@article{tsai_balke_2024, title={(Invited) Probing Local Ion Insertion through Operando AFM}, url={https://doi.org/10.1149/MA2024-01512758mtgabs}, DOI={10.1149/MA2024-01512758mtgabs}, abstractNote={Electrode volume change during ion insertion or intercalation has been one of the main failure mechanisms for several energy storage devices, especially Li-based batteries. Fundamental understanding of the relationship between the amount of the ions/charge stored and the induced volume changes of the hosting electrodes, and how this relationship impact the materials’ performance are necessary to develop the next generation batteries. However, most of the studies on the volume change were based on bulk techniques, which study the entire electrode including binders and additives. Here, we use operando atomic force microscopy (AFM), which allows tracking local volume changes and other mechanical responses with sub-nanometer spatial resolution under the conditions close to the device operation. In this work, we monitored electrode volume change via operando AFM and demonstrated the electro-chemo-mechanical coupling behaviors during proton insertion into WO 3 materials. The concept of mechanical cyclic voltammetry (mCV) curves was developed, and the relationship between electrochemical current and strain was investigated with simplified models. The results revealed multiple ion-intercalation processes with different mechanical responses are involved during electrode cycling. Local heterogeneity was investigated via mCV mapping, confirming that the charging mechanisms varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations, or chemical compositions. We further demonstrate that the mCV approach is applicable to a variety of energy storage materials (e.g., birnessite, MXene and metal nitrides) with the increasing complexity of current-deformation relationships.}, journal={ECS Meeting Abstracts}, author={Tsai, Wan-Yu and Balke, Nina}, year={2024}, month={Aug} }
 @article{ishrak_lastovich_malakar_haridas_bhattacharjee_qiao_clary_tracy_balke_lisabeth_et al._2024, title={Aluminum/SmCo<sub>5</sub> composites for structural and magnetic applications}, volume={9}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-024-10208-3}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Ishrak, Farhan and Lastovich, Michael and Malakar, Aniruddha and Haridas, Ravi Sankar and Bhattacharjee, Arun J. and Qiao, Huimin and Clary, Matthew and Tracy, Joseph and Balke, Nina and Lisabeth, Harrison P. and et al.}, year={2024}, month={Sep} }
 @misc{hausen_balke_2024, title={Current understanding of electrochemical strain microscopy to visualize ion behavior on the nanoscale}, volume={47}, ISSN={["2451-9103"]}, DOI={10.1016/j.coelec.2024.101562}, abstractNote={Electrochemical Strain Microscopy (ESM) is a technique based on Atomic Force Microscopy and provides information about local ionic processes through electro-chemo-mechanical coupling. It is employed foremost in studying battery materials, from cathodes, and anodes to solid-state electrolytes. Based on this overlap we aim to connect the electrochemistry community further with those employing ESM, by providing the current understanding of ESM, starting with a thorough introduction to the technique. In the second section, typical applications and challenges identified in recent years are reviewed while in the third chapter new approaches to overcome these issues are presented. This includes the identification of various contributions to the ESM signal, the integration of ESM as part of a multi-modal characterization approach, and importantly, how to link local ESM results to the overall cell performance in batteries. Lastly, upcoming trends and new aspects are discussed, including the application of in-situ ESM directly in an electrochemical environment.}, journal={CURRENT OPINION IN ELECTROCHEMISTRY}, author={Hausen, Florian and Balke, Nina}, year={2024}, month={Oct} }
 @article{tsai_pillai_ganeshan_saeed_gao_duin_augustyn_balke_2023, title={Effect of Electrode/Electrolyte Coupling on Birnessite (delta-MnO2) Mechanical Response and Degradation}, volume={15}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.3c02055}, DOI={10.1021/acsami.3c02055}, abstractNote={Understanding the deformation of energy storage electrodes at a local scale and its correlation to electrochemical performance is crucial for designing effective electrode architectures. In this work, the effect of electrolyte cation and electrode morphology on birnessite (δ-MnO2) deformation during charge storage in aqueous electrolytes was investigated using a mechanical cyclic voltammetry approach via operando atomic force microscopy (AFM) and molecular dynamics (MD) simulation. In both K2SO4 and Li2SO4 electrolytes, the δ-MnO2 host electrode underwent expansion during cation intercalation, but with different potential dependencies. When intercalating Li+, the δ-MnO2 electrode presents a nonlinear correlation between electrode deformation and electrode height, which is morphologically dependent. These results suggest that the stronger cation-birnessite interaction is the reason for higher local stress heterogeneity when cycling in Li2SO4 electrolyte, which might be the origin of the pronounced electrode degradation in this electrolyte.}, number={21}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Tsai, Wan-Yu and Pillai, Shelby B. B. and Ganeshan, Karthik and Saeed, Saeed and Gao, Yawei and Duin, Adri C. T. and Augustyn, Veronica and Balke, Nina}, year={2023}, month={May}, pages={26120–26127} }
 @article{o'hara_tao_neumayer_maksymovych_balke_pantelides_2022, title={Effects of thin metal contacts on few-layer van der Waals ferrielectric CuInP2S6}, volume={132}, ISSN={["1089-7550"]}, url={https://doi.org/10.1063/5.0096704}, DOI={10.1063/5.0096704}, abstractNote={Out-of-plane polarized ferroelectric materials in a capacitive structure provide a key component for several technological applications. Furthermore, two-dimensional materials are expected to aid in the quest for both ultrathin and flexible electronics. Of the various two-dimensional ferroelectrics with out-of-plane polarization, CuInP2S6 is special in that the Cu atoms are highly mobile and it has been shown to possess both low- and high-polarization states. Using density-functional-theory calculations, we explore the stabilization of the ferroelectric state for several prototypical metal contacts (Gr, Ni, Cu, Au, and Ag). In all cases, we find that the ferroelectric state can be stabilized at fewer layers than in the freestanding case. For all of the considered conventional metal contacts, we also find the existence of a quasi-ferroelectric state that stabilizes a polar phase for thicknesses greater than two layers of CIPS. In the cases of Au and Ag, interfacial alignment and strain can be used to stabilize ferroelectricity at the bilayer limit. Furthermore, we find that the strength of the interaction between the contact and CuInP2S6 also leads to stabilization of the high-polarization state when ferroelectricity is stabilized. Lastly, energy-barrier calculations show that the system is still switchable in the presence of contact doping from the metal contacts.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={O'Hara, Andrew and Tao, Lei and Neumayer, Sabine M. and Maksymovych, Petro and Balke, Nina and Pantelides, Sokrates T.}, year={2022}, month={Sep} }
 @article{neumayer_si_li_liao_tao_o'hara_pantelides_ye_maksymovych_balke_2022, title={Ionic Control over Ferroelectricity in 2D Layered van der Waals Capacitors}, volume={1}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.1c18683}, DOI={10.1021/acsami.1c18683}, abstractNote={The van der Waals layered material CuInP2S6 features interesting functional behavior, including the existence of four uniaxial polarization states, polarization reversal against the electric field through Cu ion migration, a negative-capacitance regime, and reversible extraction of Cu ions. At the heart of these characteristics lies the high mobility of Cu ions, which also determines the spontaneous polarization. Therefore, Cu migration across the lattice results in unusual ferroelectric behavior. Here, we demonstrate how the interplay of polar and ionic properties provides a path to ionically controlled ferroelectric behavior, achieved by applying selected DC voltage pulses and subsequently probing ferroelectric switching during fast triangular voltage sweeps. Using current measurements and theoretical calculations, we observe that increasing DC pulse duration results in higher ionic currents, the buildup of an internal electric field that shifts polarization loops, and an increase in total switchable polarization by ∼50% due to the existence of a high polarization phase which is stabilized by the internal electric field. Apart from tuning ferroelectric behavior by selected square pulses, hysteretic polarization switching can even be entirely deactivated and reactivated, resulting in three-state systems where polarization switching is either inhibited or can be performed in two different directions.}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Neumayer, Sabine M. and Si, Mengwei and Li, Junkang and Liao, Pai-Ying and Tao, Lei and O'Hara, Andrew and Pantelides, Sokrates T. and Ye, Peide D. and Maksymovych, Petro and Balke, Nina}, year={2022}, month={Jan} }
 @article{neumayer_zhao_o'hara_mcguire_susner_pantelides_maksymovych_balke_2022, title={Nanoscale Control of Polar Surface Phases in Layered van der Waals CuInP2S6}, volume={16}, ISSN={["1936-086X"]}, url={https://doi.org/10.1021/acsnano.1c08970}, DOI={10.1021/acsnano.1c08970}, abstractNote={Antiferroelectric (AFE) materials, in which alternating dipole moments cancel out to a zero net macroscopic polarization, can be used for high-density energy storage and memory applications. The AFE phase can exist in bulk CuInP2Se6, CuBiP2S6, and a few other transition-metal thiophosphates below 200 K. The required low temperature poses challenges for practical applications. In this work, we report the coexistence of ferrielectric (FE) states and a stable surface phase that does not show piezoelectric response ("zero-response phase") in bulk CuInP2S6 at room temperature. Using piezoresponse force microscopy (PFM) tomographic imaging together with density functional theory, we find that direct and alternating voltages can locally and stably convert FE to zero-response phases and vice versa. While PFM loops show pinched hystereses reminiscent of antiferroelectricity, PFM tomography reveals that the zero-response areas form only on top of the FE phase in which the polarization vector is pointing up. Theoretical calculations suggest that the zero-response phase may correspond to AFE ordering where stacked CuInP2S6 layers have alternating polarization orientations thereby leading to a net-zero polarization. Consistent with experimental findings, theory predicts that the FE polarization pointing down is robust up to the top surface, whereas FE polarization pointing up energetically favors the formation of an AFE surface layer, whose thickness is likely to be sensitive to local strains. AFE order is likely to be more robust against detrimental size effects than polar order, therefore providing additional opportunities to create multifunctional heterostructures with 2D electronic materials.}, number={2}, journal={ACS NANO}, publisher={American Chemical Society (ACS)}, author={Neumayer, Sabine M. and Zhao, Zhenghang and O'Hara, Andrew and McGuire, Michael A. and Susner, Michael A. and Pantelides, Sokrates T. and Maksymovych, Petro and Balke, Nina}, year={2022}, month={Feb}, pages={2452–2460} }
 @article{tsai_balke_2022, title={Probing Local Ion Insertion through Strain-Current Correlation}, url={https://doi.org/10.1149/MA2022-02562145mtgabs}, DOI={10.1149/MA2022-02562145mtgabs}, abstractNote={  	Among different electrochemical energy storage devices, the ones that store a higher amount of energy (e.g., batteries) often undergo larger ion insertion-induced structural transformation and volume change, which results in lower rate performance. The ones that store a lower amount of energy (e.g., supercapacitors) usually show gradual structural change and smaller volume change. There is a strong correlation between electrochemistry and mechanical properties. Understanding the electro-chemo-mechanical coupling and controlling the ion insertion-induced strain is crucial for achieving high power and high energy storage devices. In-situ atomic force microscopy (AFM) is well suited to tackle this task as it allows tracking local volume changes and other mechanical responses sub-nanometer spatial resolution under the conditions close to the device operation
               In this work, we monitored electrode volume change via in-situ AFM and demonstrated the electro-chemo-mechanical coupling behaviors during proton insertion into WO3 materials. The concept of mechanical cyclic voltammetry (mCV) curves was developed, and the relationship between electrochemical current and strain was investigated with simplified models. The results revealed multiple ion-intercalation processes with different mechanical responses are involved during electrode cycling. Local heterogeneity was investigated via mCV mapping, confirming that the charging mechanisms varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations, or chemical compositions. We further demonstrate that the mCV approach is applicable to a variety of energy storage materials (e.g., birnessite and MXene) with the increasing complexity of current-deformation relationships.
               The work was supported by the Fluid Interface Reactions, Structures, and Transport (FIRST), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Measurements were performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.    }, journal={ECS Meeting Abstracts}, author={Tsai, Wan-Yu and Balke, Nina}, year={2022}, month={Oct} }
 @article{wei_domingo_sun_balke_dunin-borkowski_mayer_2022, title={Progress on Emerging Ferroelectric Materials for Energy Harvesting, Storage and Conversion}, volume={5}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202201199}, abstractNote={AbstractSince the discovery of Rochelle salt a century ago, ferroelectric materials have been investigated extensively due to their robust responses to electric, mechanical, thermal, magnetic, and optical fields. These features give rise to a series of ferroelectric‐based modern device applications such as piezoelectric transducers, memories, infrared detectors, nonlinear optical devices, etc. On the way to broaden the material systems, for example, from three to two dimensions, new phenomena of topological polarity, improper ferroelectricity, magnetoelectric effects, and domain wall nanoelectronics bear the hope for next‐generation electronic devices. In the meantime, ferroelectric research has been aggressively extended to more diverse applications such as solar cells, water splitting, and CO2 reduction. In this review, the most recent research progress on newly emerging ferroelectric states and phenomena in insulators, ionic conductors, and metals are summarized, which have been used for energy storage, energy harvesting, and electrochemical energy conversion. Along with the intricate coupling between polarization, coordination, defect, and spin state, the exploration of transient ferroelectric behavior, ionic migration, polarization switching dynamics, and topological ferroelectricity, sets up the physical foundation ferroelectric energy research. Accordingly, the progress in understanding of ferroelectric physics is expected to provide insightful guidance on the design of advanced energy materials.}, journal={ADVANCED ENERGY MATERIALS}, author={Wei, Xian-Kui and Domingo, Neus and Sun, Young and Balke, Nina and Dunin-Borkowski, Rafal E. and Mayer, Joachim}, year={2022}, month={May} }
 @article{boyd_ganeshan_tsai_wu_saeed_jiang_balke_duin_augustyn_2021, title={Effects of interlayer confinement and hydration on capacitive charge storage in birnessite}, ISSN={["1476-4660"]}, url={https://doi.org/10.1038/s41563-021-01066-4}, DOI={10.1038/s41563-021-01066-4}, abstractNote={Nanostructured birnessite exhibits high specific capacitance and nearly ideal capacitive behaviour in aqueous electrolytes, rendering it an important electrode material for low-cost, high-power energy storage devices. The mechanism of electrochemical capacitance in birnessite has been described as both Faradaic (involving redox) and non-Faradaic (involving only electrostatic interactions). To clarify the capacitive mechanism, we characterized birnessite’s response to applied potential using ex situ X-ray diffraction, electrochemical quartz crystal microbalance, in situ Raman spectroscopy and operando atomic force microscope dilatometry to provide a holistic understanding of its structural, gravimetric and mechanical responses. These observations are supported by atomic-scale simulations using density functional theory for the cation-intercalated structure of birnessite, ReaxFF reactive force field-based molecular dynamics and ReaxFF-based grand canonical Monte Carlo simulations on the dynamics at the birnessite–water–electrolyte interface. We show that capacitive charge storage in birnessite is governed by interlayer cation intercalation. We conclude that the intercalation appears capacitive due to the presence of nanoconfined interlayer structural water, which mediates the interaction between the intercalated cation and the birnessite host and leads to minimal structural changes. Nanostructured birnessite exhibits high specific capacitance and, while an important electrode material for high-power energy storage devices, its capacitive mechanism remains unclear. Capacitive charge storage in birnessite is now shown to be governed by interlayer cation intercalation.}, journal={NATURE MATERIALS}, author={Boyd, Shelby and Ganeshan, Karthik and Tsai, Wan-Yu and Wu, Tao and Saeed, Saeed and Jiang, De-en and Balke, Nina and Duin, Adri C. T. and Augustyn, Veronica}, year={2021}, month={Aug} }
 @article{gao_tsai_balke_2022, title={In situ and operando force‐based atomic force microscopy for probing local functionality in energy storage materials}, volume={2}, url={https://doi.org/10.1002/elsa.202100038}, DOI={10.1002/elsa.202100038}, abstractNote={AbstractElectrochemical energy storage is the key enabling component of electric vehicles and solar‐/wind‐based energy technologies. The enhancement of energy stored requires the detailed understanding of charge storage mechanisms and local electrochemical and electromechanical phenomena over a variety of length scales from atoms to full cells. Classical electrochemical techniques, such as voltammetry, represent the macroscopic electrochemical properties, and consequently do not allow to extract important information about local electrochemical reactions, ions adsorption, intercalations, and transport. Understanding, controlling, and tuning the local electrochemical functionalities in functional energy materials require in situ/operando techniques which limit the use of structural and functional characterization techniques that provide local information. Here, force‐based atomic force microscopies (AFMs) have provided novel insights into locally probing electrochemical mechanisms on tens of nanometer and even molecular length scales and provide a viable pathway to probe electrochemical processes in situ/operando. In this review, we highlight the contributions in the development and application of force‐based AFM methods to elucidate the local charge storage mechanism in a variety of energy‐related materials. We will focus in particular on methods or AFM modalities in a liquid electrolyte environment.}, number={1}, journal={Electrochemical Science Advances}, publisher={Wiley}, author={Gao, Qiang and Tsai, Wan‐Yu and Balke, Nina}, year={2022}, month={Feb} }
 @article{schön_schierholz_jesse_yu_eichel_balke_hausen_2021, title={Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes}, url={https://doi.org/10.1002/smtd.202001279}, DOI={10.1002/smtd.202001279}, abstractNote={AbstractElectrochemical strain microscopy (ESM) is a distinguished method to characterize Li‐ion mobility in energy materials with extremely high spatial resolution. The exact origin of the cantilever deflection when the technique is applied on solid state electrolytes (SSEs) is currently discussed in the literature. Understanding local properties and influences on ion mobility in SSEs is of utmost importance to improve such materials for next generation batteries. Here, the exact signal formation process of ESM when applied on sodium super ionic conductor (NASICON)‐type SSE containing Na‐ and Li‐ions is investigated. Changes in the dielectric properties, which are linked to the local chemical composition, are found to be responsible for the observed contrast in the deflection of the cantilever instead of a physical volume change as a result of Vegard´s Law. The cantilever response is strongly reduced in areas of high sodium content which is attributed to a reduction of the tip‐sample capacitance in comparison to areas with high lithium content. This is the first time a direct link between electrostatic forces in contact mode and local chemical information is demonstrated on SSEs. The results open up new possibilities in information gain since dielectric properties are sensitive to subtle changes in local chemical composition.}, journal={Small Methods}, author={Schön, Nino and Schierholz, Roland and Jesse, Stephen and Yu, Shicheng and Eichel, Rüdiger‐A. and Balke, Nina and Hausen, Florian}, year={2021}, month={May} }
 @article{sohn_gao_vasudevan_neumayer_balke_ok_lee_skoropata_jeong_kim_et al._2021, title={Strain-driven autonomous control of cation distribution for artificial ferroelectrics}, volume={7}, url={https://doi.org/10.1126/sciadv.abd7394}, DOI={10.1126/sciadv.abd7394}, abstractNote={Strain provides autonomous control of atomic building blocks for the synthesis of functional materials.}, number={18}, journal={Science Advances}, publisher={American Association for the Advancement of Science (AAAS)}, author={Sohn, Changhee and Gao, Xiang and Vasudevan, Rama K. and Neumayer, Sabine M. and Balke, Nina and Ok, Jong Mok and Lee, Dongkyu and Skoropata, Elizabeth and Jeong, Hu Young and Kim, Young-Min and et al.}, year={2021}, month={Apr} }
 @article{wang_mathis_sun_tsai_shpigel_shao_zhang_hantanasirisakul_malchik_balke_et al._2021, title={Titanium Carbide MXene Shows an Electrochemical Anomaly in Water-in-Salt Electrolytes}, volume={8}, url={https://doi.org/10.1021/acsnano.1c06027}, DOI={10.1021/acsnano.1c06027}, abstractNote={Identifying and understanding charge storage mechanisms is important for advancing energy storage. Well-separated peaks in cyclic voltammograms (CVs) are considered key indicators of diffusion-controlled electrochemical processes with distinct Faradaic charge transfer. Herein, we report on an electrochemical system with separated CV peaks, accompanied by surface-controlled partial charge transfer, in 2D Ti3C2Tx MXene in water-in-salt electrolytes. The process involves the insertion/desertion of desolvation-free cations, leading to an abrupt change of the interlayer spacing between MXene sheets. This unusual behavior increases charge storage at positive potentials, thereby increasing the amount of energy stored. This also demonstrates opportunities for the development of high-rate aqueous energy storage devices and electrochemical actuators using safe and inexpensive aqueous electrolytes.}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Wang, Xuehang and Mathis, Tyler S. and Sun, Yangyunli and Tsai, Wan-Yu and Shpigel, Netanel and Shao, Hui and Zhang, Danzhen and Hantanasirisakul, Kanit and Malchik, Fyodor and Balke, Nina and et al.}, year={2021}, month={Sep} }
 @article{saeed_boyd_tsai_wang_balke_augustyn_2021, title={Understanding electrochemical cation insertion into prussian blue from electrode deformation and mass changes}, volume={57}, ISSN={["1364-548X"]}, url={https://doi.org/10.1039/D1CC01681D}, DOI={10.1039/D1CC01681D}, abstractNote={Alkali ion insertion into Prussian blue from aqueous electrolytes is characterized with operando AFM and EQCM, showing coupling of current with deformation and mass change rates.}, number={55}, journal={CHEMICAL COMMUNICATIONS}, publisher={Royal Society of Chemistry (RSC)}, author={Saeed, Saeed and Boyd, Shelby and Tsai, Wan-Yu and Wang, Ruocun and Balke, Nina and Augustyn, Veronica}, year={2021}, month={Jul}, pages={6744–6747} }
 @article{augustyn_wang_balke_pharr_arnold_2020, title={Deformation during Electrosorption and Insertion-Type Charge Storage: Origins, Characterization, and Design of Materials for High Power}, volume={5}, url={https://doi.org/10.1021/acsenergylett.0c01823}, DOI={10.1021/acsenergylett.0c01823}, abstractNote={Ion electrosorption and insertion form the basis of two commercialized electrochemical energy storage technologies: electric double-layer capacitors and lithium ion batteries. These processes are a...}, number={11}, journal={ACS Energy Letters}, publisher={American Chemical Society (ACS)}, author={Augustyn, Veronica and Wang, Ruocun and Balke, Nina and Pharr, Matt and Arnold, Craig B.}, year={2020}, month={Nov}, pages={3548–3559} }
 @article{vasudevan_neumayer_susner_mcguire_pantelides_maksymovych_leonard_balke_borisevich_2020, title={Domains and Topological Defects in Layered Ferrielectric Materials: Implications for Nanoelectronics}, volume={3}, url={https://doi.org/10.1021/acsanm.0c01577}, DOI={10.1021/acsanm.0c01577}, abstractNote={Topological defects in materials present unique opportunities for nanoelectronics, as they allow us to harness new functionalities unavailable in the pristine bulk. However, their study in layered ...}, number={8}, journal={ACS Applied Nano Materials}, publisher={American Chemical Society (ACS)}, author={Vasudevan, Rama K. and Neumayer, Sabine M. and Susner, Michael A. and McGuire, Michael A. and Pantelides, Sokrates T. and Maksymovych, Petro and Leonard, Donovan N. and Balke, Nina and Borisevich, Albina Y.}, year={2020}, month={Aug}, pages={8161–8166} }
 @article{kelley_ren_morozovska_eliseev_ehara_funakubo_giamarchi_balke_vasudevan_cao_et al._2020, title={Dynamic Manipulation in Piezoresponse Force Microscopy: Creating Nonequilibrium Phases with Large Electromechanical Response}, volume={14}, url={https://doi.org/10.1021/acsnano.0c04601}, DOI={10.1021/acsnano.0c04601}, abstractNote={Domain walls and topological defects in ferroelectric materials have emerged as a powerful tool for functional electronic devices including memory and logic. Similarly, wall interactions and dynamics underpin a broad range of mesoscale phenomena ranging from giant electromechanical responses to memory effects. Exploring the functionalities of individual domain walls, their interactions, and controlled modifications of the domain structures is crucial for applications and fundamental physical studies. However, the dynamic nature of these features severely limits studies of their local physics since application of local biases or pressures in piezoresponse force microscopy induce wall displacement as a primary response. Here, we introduce an approach for the control and modification of domain structures based on automated experimentation, whereby real-space image-based feedback is used to control the tip bias during ferroelectric switching, allowing for modification routes conditioned on domain states under the tip. This automated experiment approach is demonstrated for the exploration of domain wall dynamics and creation of metastable phases with large electromechanical response.}, number={8}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Kelley, Kyle P. and Ren, Yao and Morozovska, Anna N. and Eliseev, Eugene A. and Ehara, Yoshitaka and Funakubo, Hiroshi and Giamarchi, Thierry and Balke, Nina and Vasudevan, Rama K. and Cao, Ye and et al.}, year={2020}, month={Aug}, pages={10569–10577} }
 @article{neumayer_susner_mcguire_pantelides_kalnaus_maksymovych_balke_2021, title={Lowering of Tc in Van Der Waals Layered Materials Under In-Plane Strain}, volume={68}, url={https://doi.org/10.1109/TUFFC.2020.3007290}, DOI={10.1109/TUFFC.2020.3007290}, abstractNote={The dependence of electromechanical behavior on strain in ferroelectric materials can be leveraged as parameter to tune ferroelectric properties such as the Curie temperature. For van der Waals materials, a unique opportunity arises because of wrinkling, bubbling, and Moiré phenomena accessible due to structural properties inherent to the van der Waals gap. Here, we use piezoresponse force microscopy and unsupervised machine learning methods to gain insight into the ferroelectric properties of layered CuInP2S6 where local areas are strained in-plane due to a partial delamination, resulting in a topographic bubble feature. We observe significant differences between strained and unstrained areas in piezoresponse images as well as voltage spectroscopy, during which strained areas show a sigmoid-shaped response usually associated with the response measured around the Curie temperature, indicating a lowering of the Curie temperature under tensile strain. These results suggest that strain engineering might be used to further increase the functionality of CuInP2S6 through locally modifying ferroelectric properties on the micro- and nanoscale.}, number={2}, journal={IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Neumayer, Sabine M. and Susner, Michael A. and McGuire, Michael A. and Pantelides, Sokrates T. and Kalnaus, Sergiy and Maksymovych, Petro and Balke, Nina}, year={2021}, month={Feb}, pages={253–258} }
 @article{borodinov_tsai_korolkov_balke_kalinin_ovchinnikova_2020, title={Machine learning-based multidomain processing for texture-based image segmentation and analysis}, url={https://doi.org/10.1063/1.5135328}, DOI={10.1063/1.5135328}, abstractNote={Atomic and molecular resolved atomic force microscopy (AFM) images offer unique insights into materials' properties such as local ordering, molecular orientation, and topological defects, which can be used to pinpoint physical and chemical interactions occurring at the surface. Utilizing machine learning for extracting underlying physical parameters increases the throughput of AFM data processing and eliminates inconsistencies intrinsic to manual image analysis, thus enabling the creation of reliable frameworks for qualitative and quantitative evaluation of experimental data. Here, we present a robust and scalable approach to the segmentation of AFM images based on flexible pre-selected classification criteria. The usage of supervised learning and feature extraction allows us to retain the consideration of specific problem-dependent features (such as types of periodical structures observed in the images and the associated numerical parameters: spacing, orientation, etc.). We highlight the applicability of this approach for the segmentation of molecular resolved AFM images based on the crystal orientation of the observed domains, automated selection of boundaries, and collection of relevant statistics. Overall, we outline a general strategy for machine learning-enabled analysis of nanoscale systems exhibiting periodic order that could be applied to any analytical imaging technique.}, journal={Applied Physics Letters}, author={Borodinov, Nikolay and Tsai, Wan-Yu and Korolkov, Vladimir V. and Balke, Nina and Kalinin, Sergei V. and Ovchinnikova, Olga S.}, year={2020}, month={Jan} }
 @article{dixit_zaman_hortance_vujic_harkey_shen_tsai_andrade_chen_balke_et al._2020, title={Nanoscale Mapping of Extrinsic Interfaces in Hybrid Solid Electrolytes}, volume={4}, DOI={10.1016/j.joule.2019.11.015}, abstractNote={Inorganic-organic hybrid solid electrolytes are promising material systems for all solid-state batteries (ASSBs). These electrolytes contain numerous solid|solid interfaces that govern transport pathways, electrode|electrolyte compatibility, and durability. This paper evaluates the role that electrode|electrolyte interfaces and electrolyte structure have on electrochemical performance. Atomic force microscopy techniques reveal how mechanical, adhesion, and morphological properties transform in a series of model hybrid solid electrolytes. These measurements are mapped to sub-surface microstructural features using synchrotron nano-tomography. Hybrid solid electrolytes with shorter polymer chains demonstrate a higher adhesion (>100 nN), Young’s Modulus (6.4 GPa), capacity (114.6 mAh/g), and capacity retention (92.9%) than hybrid electrolytes with longer polymer chains (i.e., higher molecular weight). Extrinsic interfacial properties largely dictate electrochemical performance in ASSBs. Microstructural control over inorganic constituents may provide a means for tailoring interfacial properties in hybrid solid electrolytes.}, number={1}, journal={Joule}, publisher={Elsevier BV}, author={Dixit, Marm B. and Zaman, Wahid and Hortance, Nicholas and Vujic, Stella and Harkey, Brice and Shen, Fengyu and Tsai, Wan-Yu and Andrade, Vincent De and Chen, X. Chelsea and Balke, Nina and et al.}, year={2020}, month={Jan}, pages={207–221} }
 @article{neumayer_saremi_martin_collins_tselev_jesse_kalinin_balke_2020, title={Piezoresponse amplitude and phase quantified for electromechanical characterization}, url={https://doi.org/10.1063/5.0011631}, DOI={10.1063/5.0011631}, abstractNote={Piezoresponse force microscopy (PFM) is a powerful characterization technique to readily image and manipulate the ferroelectric domains. PFM gives an insight into the strength of local piezoelectric coupling and polarization direction through PFM amplitude and phase, respectively. Converting measured arbitrary units into units of effective piezoelectric constant remains a challenge, and insufficient methods are often used. While most quantification efforts have been spent on quantifying the PFM amplitude signal, little attention has been given to the PFM phase, which is often arbitrarily adjusted to fit expectations. This is problematic when investigating materials with unknown or negative sign of the probed effective electrostrictive coefficient or strong frequency dispersion of electromechanical responses, because assumptions about the PFM phase cannot be reliably made. The PFM phase can, however, provide important information on the polarization orientation and the sign of the effective electrostrictive coefficient probed by PFM. Most notably, the orientation of the PFM hysteresis loop is determined by the PFM phase. Moreover, when presenting PFM data as a combined signal, the resulting response can be artificially lowered or asymmetric if the phase data have not been correctly processed. Here, we explain the PFM amplitude quantification process and demonstrate a path to identify the phase offset required to extract correct meaning from the PFM phase data. We explore different sources of phase offsets including the experimental setup, instrumental contributions, and data analysis. We discuss the physical working principles of PFM and develop a strategy to extract physical meaning from the PFM amplitude and phase.}, journal={Journal of Applied Physics}, author={Neumayer, Sabine M. and Saremi, Sahar and Martin, Lane W. and Collins, Liam and Tselev, Alexander and Jesse, Stephen and Kalinin, Sergei V. and Balke, Nina}, year={2020}, month={Nov} }
 @article{barbosa_balke_tsai_santato_orlandi_2020, title={Structure of the Electrical Double Layer at the Interface between an Ionic Liquid and Tungsten Oxide in Ion-Gated Transistors}, volume={11}, url={https://doi.org/10.1021/acs.jpclett.0c00651}, DOI={10.1021/acs.jpclett.0c00651}, abstractNote={The structure of electrical double layers at electrified interfaces is of utmost importance for electrochemical energy storage as well as printable, flexible and bio-electronic devices, such as ion-gated transistors, IGTs. Here we report on a study based on Atomic Force Microscopy Force-Distance profiling on electrical double layers forming at the interface between the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]) and sol-gel films of mesoporous tungsten oxide. We successfully followed, in operando conditions, the evolution of the arrangement of the ions at the inter-face with the tungsten oxide films used as channel materials in ion-gated transistors. Our work sheds light on the operation mechanism of IGTs thus offering the possibility to optimize their performance.}, number={9}, journal={The Journal of Physical Chemistry Letters}, publisher={American Chemical Society (ACS)}, author={Barbosa, Martin S. and Balke, Nina and Tsai, Wan-Yu and Santato, Clara and Orlandi, Marcelo O.}, year={2020}, month={May}, pages={3257–3262} }
 @article{neumayer_jesse_velarde_kholkin_kravchenko_martin_balke_maksymovych_2020, title={To switch or not to switch – a machine learning approach for ferroelectricity}, volume={2}, url={https://doi.org/10.1039/C9NA00731H}, DOI={10.1039/C9NA00731H}, abstractNote={The introduced two-dimensional representation of two-parameter signal dependence allows for clear interpretation and classification of the measured signal upon using machine learning methods.}, number={5}, journal={Nanoscale Advances}, publisher={Royal Society of Chemistry (RSC)}, author={Neumayer, Sabine M. and Jesse, Stephen and Velarde, Gabriel and Kholkin, Andrei L. and Kravchenko, Ivan and Martin, Lane W. and Balke, Nina and Maksymovych, Peter}, year={2020}, pages={2063–2072} }
 @article{sharma_holt_laanait_gao_ivanov_collins_sohn_liao_skoropata_kalinin_et al._2019, title={Competing phases in epitaxial vanadium dioxide at nanoscale}, volume={7}, DOI={10.1063/1.5115784}, abstractNote={Phase competition in correlated oxides offers tantalizing opportunities as many intriguing physical phenomena occur near the phase transitions. Owing to a sharp metal-insulator transition (MIT) near room temperature, the correlated vanadium dioxide (VO2) exhibits a strong competition between insulating and metallic phases, which is important for practical applications. However, the phase boundary undergoes a strong modification when strain is involved, yielding complex phase transitions. Here, we report the emergence of nanoscale M2 phase domains in VO2 epitaxial films under anisotropic strain relaxation. The competing phases of the films are imaged by multilength-scale probes, detecting the structural and electrical properties in individual local domains. Competing evolution of the M1 and M2 phases indicates the critical role of lattice-strain on both the stability of the M2 Mott phase and the energetics of the MIT in VO2 films. This study demonstrates how strain engineering can be utilized to design phase states, which allow deliberate control of MIT behavior at the nanoscale in epitaxial VO2 films.}, number={8}, journal={APL Materials}, publisher={AIP Publishing}, author={Sharma, Yogesh and Holt, Martin V. and Laanait, Nouamane and Gao, Xiang and Ivanov, Ilia N. and Collins, Liam and Sohn, Changhee and Liao, Zhaoliang and Skoropata, Elizabeth and Kalinin, Sergei V. and et al.}, year={2019}, month={Aug}, pages={081127} }
 @article{herklotz_rus_wisinger_rouleau_guo_huon_santosh_roth_yang_vaswani_et al._2019, title={Correction to Designing Morphotropic Phase Composition in BiFeO3}, volume={19}, url={https://doi.org/10.1021/acs.nanolett.9b02023}, DOI={10.1021/acs.nanolett.9b02023}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to Designing Morphotropic Phase Composition in BiFeO3Andreas HerklotzAndreas HerklotzMore by Andreas Herklotzhttp://orcid.org/0000-0002-1545-131X, Stefania F. RusStefania F. RusMore by Stefania F. Rus, Nina Balke WisingerNina Balke WisingerMore by Nina Balke Wisingerhttp://orcid.org/0000-0001-5865-5892, Christopher RouleauChristopher RouleauMore by Christopher Rouleau, Er-Jia GuoEr-Jia GuoMore by Er-Jia Guo, Amanda HuonAmanda HuonMore by Amanda Huon, Santosh KCSantosh KCMore by Santosh KC, Robert RothRobert RothMore by Robert Rothhttp://orcid.org/0000-0002-7352-2067, Xu YangXu YangMore by Xu Yang, Chirag VaswaniChirag VaswaniMore by Chirag Vaswani, Jigang WangJigang WangMore by Jigang Wang, Peter P. OrthPeter P. OrthMore by Peter P. Orth, Mathias S. ScheurerMathias S. ScheurerMore by Mathias S. Scheurer, and Thomas Z. Ward*Thomas Z. WardMore by Thomas Z. Wardhttp://orcid.org/0000-0002-1027-9186Cite this: Nano Lett. 2019, 19, 6, 4211Publication Date (Web):May 31, 2019Publication History Published online31 May 2019Published inissue 12 June 2019https://pubs.acs.org/doi/10.1021/acs.nanolett.9b02023https://doi.org/10.1021/acs.nanolett.9b02023correctionACS PublicationsCopyright © 2019 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views1008Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (239 KB) Get e-Alertsclose Get e-Alerts}, number={6}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Herklotz, Andreas and Rus, Stefania F. and Wisinger, Nina Balke and Rouleau, Christopher and Guo, Er-Jia and Huon, Amanda and Santosh, KC and Roth, Robert and Yang, Xu and Vaswani, Chirag and et al.}, year={2019}, month={Jun}, pages={4211–4211} }
 @article{herklotz_rus_balke_rouleau_guo_huon_santosh_roth_yang_vaswani_et al._2019, title={Designing Morphotropic Phase Composition in BiFeO3}, volume={19}, url={https://doi.org/10.1021/acs.nanolett.8b04322}, DOI={10.1021/acs.nanolett.8b04322}, abstractNote={In classical morphotropic piezoelectric materials, rhombohedral and tetragonal phase variants can energetically compete to form a mixed phase regime with improved functional properties. While the discovery of morphotropic-like phases in multiferroic BiFeO3 films has broadened this definition, accessing these phase spaces is still typically accomplished through isovalent substitution or heteroepitaxial strain which do not allow for continuous modification of phase composition postsynthesis. Here, we show that it is possible to use low-energy helium implantation to tailor morphotropic phases of epitaxial BiFeO3 films postsynthesis in a continuous and iterative manner. Applying this strain doping approach to morphotropic films creates a new phase space based on internal and external lattice stress that can be seen as an analogue to temperature-composition phase diagrams of classical morphotropic ferroelectric systems.}, number={2}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Herklotz, Andreas and Rus, Stefania F. and Balke, Nina and Rouleau, Christopher and Guo, Er-Jia and Huon, Amanda and Santosh, KC and Roth, Robert and Yang, Xu and Vaswani, Chirag and et al.}, year={2019}, month={Feb}, pages={1033–1038} }
 @article{neumayer_eliseev_susner_tselev_rodriguez_brehm_pantelides_panchapakesan_jesse_kalinin_et al._2019, title={Giant negative electrostriction and dielectric tunability in a van der Waals layered ferroelectric}, volume={3}, DOI={10.1103/physrevmaterials.3.024401}, abstractNote={The interest in ferroelectric van der Waals crystals arises from the potential to realize ultrathin ferroic systems owing to the reduced surface energy of these materials and the layered structure that allows for exfoliation. Here, we reveal giant negative electrostriction of van der Waals layered copper indium thiophosphate (CIPS), with an electrostrictive coefficient Q33 as high as -3.2 m$^{4}$/C$^{2}$ and the resulting bulk piezoelectric coefficient d$_{33}$ of -85 pm/V. As a result, the electromechanical response of CIPS is comparable in magnitude to established perovskite ferroelectrics despite possessing a much smaller spontaneous polarization of only a few $\mu$C/cm$^{2}$. Moreover, in the paraelectric state, readily accessible owing to low transition temperature, CIPS exhibits large dielectric tenability, similar to widely-used barium strontium titanate, and as a result both giant and continuously tunable electromechanical response. The persistence of electrostrictive and tunable responses in the paraelectric state indicates that even few layer films or nanoparticles will sustain significant electromechanical functionality, offsetting the inevitable suppression of ferroelectric properties in the nanoscale limit. These findings can likely be extended to other ferroelectric transition metal thiophosphates and (quasi-) two-dimensional materials and might facilitate the quest towards novel ultrathin functional devices incorporating electromechanical response.}, number={2}, journal={Physical Review Materials}, publisher={American Physical Society (APS)}, author={Neumayer, Sabine M. and Eliseev, Eugene A. and Susner, Michael A. and Tselev, Alexander and Rodriguez, Brian J. and Brehm, John A. and Pantelides, Sokrates T. and Panchapakesan, Ganesh and Jesse, Stephen and Kalinin, Sergei V. and et al.}, year={2019}, month={Feb} }
 @article{tsai_come_zhao_wang_feng_thapaliya_dai_collins_balke_2019, title={Hysteretic order-disorder transitions of ionic liquid double layer structure on graphite}, volume={60}, DOI={10.1016/j.nanoen.2019.04.022}, abstractNote={Understanding the electrical double layer (EDL) structure at the solid/liquid interface is critical towards realizing the full potential of electrochemical applications using ionic liquids. In this work, the out-of-plane and in-plane EDL structures of PYR14-TFSI on graphite (HOPG) have been studied by in-situ electrochemical atomic force microscopy (AFM) and molecular dynamics (MD) simulation. AFM results revealed that the first adsorbed ion layer on HOPG consists of both disordered and ordered lateral domains. It has been found that the neighboring molecules in the x-y plane form intricate ordered lateral structures on length scale of hundreds of nanometers, and the out-of-plane EDL structure is independent of the in-plane structure. MD simulations under zero polarization showed that in the first adsorbed layer, cations have one preferred orientation while anions have two preferred orientations in relation to the HOPG surface, which might be the origin of the complex lateral ordering. When polarizing the surface, a hysteretic order-disorder transition of the lateral ordering in the first adsorbed layer can be observed by in-situ AFM, and the ordered domains disappear for high positive or negative voltages. Comparison with bias-dependent MD reveals that the existence of a bimodal anion distribution in the first absorbed layer can be linked to the observed transitions giving new insights into the origin of the structural domains, which can help understand unusual charge and discharge kinetics observed in similar systems.}, journal={Nano Energy}, publisher={Elsevier BV}, author={Tsai, Wan-Yu and Come, Jeremy and Zhao, Wei and Wang, Runxi and Feng, Guang and Thapaliya, Bishnu Prasad and Dai, Sheng and Collins, Liam and Balke, Nina}, year={2019}, month={Jun}, pages={886–893} }
 @article{sharma_wong_herklotz_lee_ievlev_collins_lee_dai_balke_rack_et al._2019, title={Ionic Gating of Ultrathin and Leaky Ferroelectrics}, volume={6}, DOI={10.1002/admi.201801723}, abstractNote={Ionic liquids are used to induce reversible large area polarization switching in ultrathin and highly defective ferroelectric films. Long range electrostatic charge control is induced by modifying the electric double layer at an ionic liquid–PbZr0.2Ti0.8O3 interface with electrostatic and electrochemical control of polarization orientation in the ferroelectric layer. The localized nature of the ionic gating mechanism prohibits the presence of leakage current, which has historically limited the switching of ultrathin and/or electrically leaky ferroelectric films in solid metal‐gated capacitor devices. This is demonstrated on ultrathin films and in massively defective films with >30% coverage of direct conducting channels running from surface to ground. This approach opens new design possibilities for integrating ultrathin ferroelectric films in functional electronic devices.}, number={5}, journal={Advanced Materials Interfaces}, publisher={Wiley}, author={Sharma, Yogesh and Wong, Anthony T. and Herklotz, Andreas and Lee, Dongkyu and Ievlev, Anton V. and Collins, Liam and Lee, Ho Nyung and Dai, Sheng and Balke, Nina and Rack, Philip D. and et al.}, year={2019}, month={Jan}, pages={1801723} }
 @article{si_saha_liao_gao_neumayer_jian_qin_wisinger_wang_maksymovych_et al._2019, title={Room-Temperature Electrocaloric Effect in Layered Ferroelectric CuInP2S6 for Solid-State Refrigeration}, volume={13}, url={https://doi.org/10.1021/acsnano.9b01491}, DOI={10.1021/acsnano.9b01491}, abstractNote={A material with reversible temperature change capability under an external electric field, known as the electrocaloric effect (ECE), has long been considered as a promising solid-state cooling solution. However, electrocaloric (EC) performance of EC materials generally is not sufficiently high for real cooling applications. As a result, exploring new EC materials with high performance is of great interest and importance. Here, we report on the ECE of a new class of EC material, the 2D ferroelectric materials (CuInP2S6 or CIPS in this work in particular) for the first time. Over 60% polarization charge change is observed within a temperature change of only 10 K at Curie temperature, as the result of a second order phase transition in CIPS. Large adiabatic temperature change (|ΔT|) of 3.3 K, isothermal entropy change (|ΔS|) of 5.8 J kg-1 K-1 at |ΔE|=142.0 kV cm-1 at 315 K (above and near room temperature) are achieved, with a large EC strength (|ΔT|/|ΔE|) of 29.5 mK cm kV-1. The ECE of CIPS is also investigated theoretically by numerical simulation and a further EC performance projection is provided.}, number={8}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Si, Mengwei and Saha, Atanu K. and Liao, Pai-Ying and Gao, Shengjie and Neumayer, Sabine M. and Jian, Jie and Qin, Jingkai and Wisinger, Nina Balke and Wang, Haiyan and Maksymovych, Petro and et al.}, year={2019}, month={Aug}, pages={8760–8765} }
 @article{kalinin_dyck_balke_neumayer_tsai_vasudevan_lingerfelt_ahmadi_ziatdinov_mcdowell_et al._2019, title={Toward Electrochemical Studies on the Nanometer and Atomic Scales: Progress, Challenges, and Opportunities}, volume={13}, url={https://doi.org/10.1021/acsnano.9b02687}, DOI={10.1021/acsnano.9b02687}, abstractNote={Electrochemical reactions and ionic transport underpin the operation of a broad range of devices and applications, from energy storage and conversion to information technologies, as well as biochemical processes, artificial muscles, and soft actuators. Understanding the mechanisms governing function of these applications requires probing local electrochemical phenomena on the relevant time and length scales. Here, we discuss the challenges and opportunities for extending electrochemical characterization probes to the nanometer and ultimately atomic scales, including challenges in down-scaling classical methods, the emergence of novel probes enabled by nanotechnology and based on emergent physics and chemistry of nanoscale systems, and the integration of local data into macroscopic models. Scanning probe microscopy (SPM) methods based on strain detection, potential detection, and hysteretic current measurements are discussed. We further compare SPM to electron beam probes and discuss the applicability of electron beam methods to probe local electrochemical behavior on the mesoscopic and atomic levels. Similar to a SPM tip, the electron beam can be used both for observing behavior and as an active electrode to induce reactions. We briefly discuss new challenges and opportunities for conducting fundamental scientific studies, matter patterning, and atomic manipulation arising in this context.}, number={9}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Kalinin, Sergei V. and Dyck, Ondrej and Balke, Nina and Neumayer, Sabine and Tsai, Wan-Yu and Vasudevan, Rama and Lingerfelt, David and Ahmadi, Mahshid and Ziatdinov, Maxim and McDowell, Matthew T. and et al.}, year={2019}, month={Sep}, pages={9735–9780} }
 @article{brehm_neumayer_tao_andrew_chyasnavichus_susner_mcguire_kalinin_jesse_ganesh_et al._2019, title={Tunable quadruple-well ferroelectric van der Waals crystals}, volume={19}, DOI={10.1038/s41563-019-0532-z}, abstractNote={The family of layered thio- and seleno-phosphates has gained attention as potential control dielectrics for the rapidly growing family of two-dimensional and quasi-two-dimensional electronic materials. Here we report a combination of density functional theory calculations, quantum molecular dynamics simulations and variable-temperature, -pressure and -bias piezoresponse force microscopy data to predict and verify the existence of an unusual ferroelectric property—a uniaxial quadruple potential well for Cu displacements—enabled by the van der Waals gap in copper indium thiophosphate (CuInP2S6). The calculated potential energy landscape for Cu displacements is strongly influenced by strain, accounting for the origin of the negative piezoelectric coefficient and rendering CuInP2S6 a rare example of a uniaxial multi-well ferroelectric. Experimental data verify the coexistence of four polarization states and explore the temperature-, pressure- and bias-dependent piezoelectric and ferroelectric properties, which are supported by bias-dependent molecular dynamics simulations. These phenomena offer new opportunities for both fundamental studies and applications in data storage and electronics. The atomic displacements that generate ferroelectricity in materials commonly fit a double-well potential energy surface. Here, ferroelectricity in two-dimensional CuInP2S6 is shown to fit a quadruple well due to the van der Waals gap between layers of this material.}, number={1}, journal={Nature Materials}, publisher={Springer Science and Business Media LLC}, author={Brehm, John A. and Neumayer, Sabine M. and Tao, Lei and Andrew, O’Hara and Chyasnavichus, Marius and Susner, Michael A. and McGuire, Michael A. and Kalinin, Sergei V. and Jesse, Stephen and Ganesh, Panchapakesan and et al.}, year={2019}, month={Nov}, pages={43–48} }
 @article{li_lu_schiemer_laanait_balke_zhang_ren_carpenter_wen_li_et al._2018, title={Giant thermally-enhanced electrostriction and polar surface phase in La2Mo2O9 oxygen ion conductors}, volume={2}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000432992000002&KeyUID=WOS:000432992000002}, DOI={10.1103/PhysRevMaterials.2.041403}, abstractNote={Q.L. and H.W. were supported by the US Department of Energy, Office of Science, Materials Science and Engineering Division. T.L. and Y.L. acknowledge the support of the Australian Research Council (ARC) in the form of Discovery Projects (DP160104780). N.L. was supported by the Eugene P. Wigner Fellowship program at ORNL (No. DE-AC05-00OR22725). The PFM experiments were performed at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility at Oak Ridge National Laboratory (ORNL). The use of Advanced Photon Source was supported by the US DOE, Basic Energy Science under Contract No. DE-AC02-06CH11357.}, number={4}, journal={Physical Review Materials}, author={Li, Q. and Lu, T. and Schiemer, J. and Laanait, N. and Balke, N. and Zhang, Z. and Ren, Y. and Carpenter, M. A. and Wen, H. D. and Li, J. Y. and et al.}, year={2018} }
 @article{shi_collins_feng_zhang_balke_liaw_yang_2018, title={Homogenization of AlxCoCrFeNi high-entropy alloys with improved corrosion resistance}, volume={133}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000429764100012&KeyUID=WOS:000429764100012}, DOI={10.1016/j.corsci.2018.01.030}, abstractNote={The present work investigates the homogenization effect of 1250 °C heat treatment on the AlxCoCrFeNi high-entropy alloys (HEAs). The multi-phase microstructures with chemical segregations are inevitable with the increased Al content in the alloys, which cause work function variations and localized corrosion. After heat treatment, the homogenization effect revealed by the microstructure simplification and chemical-segregation reduction leads to the decreased work function variations and the improved corrosion resistance. Thermodynamic calculations that are reliable to predict the phase transformations of the AlxCoCrFeNi HEAs, indicates a further enhancement in corrosion resistance through annealing could be guided for many other HEAs systems.}, journal={Corrosion Science}, author={Shi, Y. Z. and Collins, L. and Feng, R. and Zhang, C. and Balke, N. and Liaw, P. K. and Yang, B.}, year={2018}, pages={120–131} }
 @article{moreno_bootwala_tsai_gao_shen_balke_hatzell_hatzell_2018, title={In Situ Electrochemical Dilatometry of Phosphate Anion Electrosorption}, volume={5}, url={https://doi.org/10.1021/acs.estlett.8b00542}, DOI={10.1021/acs.estlett.8b00542}, abstractNote={Here we investigate the competitive electrosorption of mono- and divalent phosphate anions through electrochemical desalination- and dilatometry-based experiments. Through in situ dilatometry, we monitor the strain at the electrode surface as anions and cations are electrosorbed. Strain measurements show that the presence of divalent ions promotes a greater than anticipated electrode expansion during cation (Na+) electrosorption. The expansion observed with Na+ equaled the expansion observed with HPO42–. Because the ionic radius of Na+ is smaller than that of HPO42–, the symmetric expansion suggests that divalent anions do not completely desorb during electrode regeneration, causing the adverse interactions with the cation during co-ion expulsion. This results in a decrease in desalination performance, indicated by a decreased salt adsorption capacity. Conversely, an expected asymmetric expansion during anion and cation electrosorption occurs with monovalent phosphate anions (H2PO4–), indicating that mono...}, number={12}, journal={Environmental Science & Technology Letters}, publisher={American Chemical Society (ACS)}, author={Moreno, Daniel and Bootwala, Yousuf and Tsai, Wan-Yu and Gao, Qiang and Shen, Fengyu and Balke, Nina and Hatzell, Kelsey B. and Hatzell, Marta C.}, year={2018}, month={Dec}, pages={745–749} }
 @article{shi_collins_balke_liaw_yang_2018, title={In-situ electrochemical-AFM study of localized corrosion of AlxCoCrFeNi high-entropy alloys in chloride solution}, volume={439}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000427457100066&KeyUID=WOS:000427457100066}, DOI={10.1016/j.apsusc.2018.01.047}, abstractNote={In-situ electrochemical (EC)-AFM is employed to investigate the localized corrosion of the AlxCoCrFeNi high-entropy alloys (HEAs). Surface topography changes on the micro/sub-micro scale are monitored at different applied anodizing potentials in a 3.5 wt% NaCl solution. The microstructural evolutions with the increased Al content in the alloys are characterized by SEM, TEM, EDS and EBSD. The results show that by increasing the Al content, the microstructure changes from single solid-solution to multi-phases, leading to the segregations of elements. Due to the microstructural variations in the AlxCoCrFeNi HEAs, localized corrosion processes in different ways after the breakdown of the passive film, which changes from pitting to phase boundary corrosion. The XPS results indicate that an increased Al content in the alloys/phases corresponds to a decreased corrosion resistance of the surface passive film.}, journal={Applied Surface Science}, author={Shi, Y. Z. and Collins, L. and Balke, N. and Liaw, P. K. and Yang, B.}, year={2018}, pages={533–544} }
 @article{dugger_collins_welbourn_skoda_balke_lokitz_browning_2018, title={Ion movement in thin Nafion films under an applied electric field}, volume={113}, url={https://doi.org/10.1063/1.5042211}, DOI={10.1063/1.5042211}, abstractNote={The electromechanical response of Nafion films with and without an ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) ([emim]Tf2N) additive were characterized under an applied electric field in situ using neutron reflectometry (NR) and voltage modulated atomic force microscopy (VM-AFM). NR showed that pure Nafion films exhibited no response under field strengths of ∼0.18 V/μm, while VM-AFM measurements showed a minimal response at higher field strengths (∼200 V/μm), which is ascribed to the residual water presence in the films. The addition of ionic liquid resulted in clear electroresponsiveness seen in both NR and VM-AFM. NR results indicated mass migration away from the cathodic interface driven by the [emim]+ movement in the direction of the electric field. The lack of ionic liquid accumulation at the electrode interfaces contrasts the bulk electromechanical behavior of similar systems reported in the literature. VM-AFM measurements were able to resolve the relative contributions of the [emim]+ cation and Tf2N− anion to film deformation by alternating the direction of the applied field and support the [emim]+ dominant migration seen in the NR results. The findings presented here emphasize the need for the nanoscale analysis of material properties of electroresponsive thin film systems and demonstrate the potential for probing electric field effects using in situ techniques.}, number={11}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Dugger, Jason W. and Collins, Liam and Welbourn, Rebecca J. L. and Skoda, Maximilian W. A. and Balke, Nina and Lokitz, Bradley S. and Browning, James F.}, year={2018}, month={Sep}, pages={113105} }
 @article{balke_neumayer_brehm_susner_rodriguez_jesse_kalinin_pantelides_mcguire_maksymovych_2018, title={Locally Controlled Cu-Ion Transport in Layered Ferroelectric CuInP2S6}, volume={10}, url={https://doi.org/10.1021/acsami.8b08079}, DOI={10.1021/acsami.8b08079}, abstractNote={Metal thiophosphates are attracting growing attention in the context of quasi-two-dimensional van der Waals functional materials. Alkali thiophosphates are investigated as ion conductors for solid electrolytes, and transition-metal thiophosphates are explored as a new class of ferroelectric materials. For the latter, a representative copper indium thiophosphate is ferrielectric at room temperature and, despite low polarization, exhibits giant negative electrostrictive coefficients. Here, we reveal that ionic conductivity in this material enables localized extraction of Cu ions from the lattice with a biased scanning probe microscopy tip, which is surprisingly reversible. The ionic conduction is tracked through local volume changes with a scanning probe microscopy tip providing a current-free probing technique, which can be explored for other thiophosphates of interest. Nearly 90 nm-tall crystallites can be formed and erased reversibly on the surface of this material as a result of ionic motion, the size of which can be sensitively controlled by both magnitude and frequency of the electric field, as well as the ambient temperature. These experimental results and density functional theory calculations point to a remarkable resilience of CuInP2S6 to large-scale ionic displacement and Cu vacancies, in part enabled by the metastability of Cu-deficient phases. Furthermore, we have found that the piezoelectric response of CuInP2S6 is enhanced by about 45% when a slight ionic modification is carried out with applied field. This new mode of modifying the lattice of CuInP2S6, and more generally ionically conducting thiophosphates, posits new prospects for their applications in van der Waals heterostructures, possibly in the context of catalytic or electronic functionalities.}, number={32}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Balke, Nina and Neumayer, Sabine M. and Brehm, John A. and Susner, Michael A. and Rodriguez, Brian J. and Jesse, Stephen and Kalinin, Sergei V. and Pantelides, Sokrates T. and McGuire, Michael A. and Maksymovych, Petro}, year={2018}, month={Aug}, pages={27188–27194} }
 @article{agar_cao_naul_pandya_walt_luo_maher_balke_jesse_kalinin_et al._2018, title={Machine Detection of Enhanced Electromechanical Energy Conversion in PbZr0.2Ti0.8O3 Thin Films}, volume={30}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000439994500018&KeyUID=WOS:000439994500018}, DOI={10.1002/adma.201800701}, abstractNote={AbstractMany energy conversion, sensing, and microelectronic applications based on ferroic materials are determined by the domain structure evolution under applied stimuli. New hyperspectral, multidimensional spectroscopic techniques now probe dynamic responses at relevant length and time scales to provide an understanding of how these nanoscale domain structures impact macroscopic properties. Such approaches, however, remain limited in use because of the difficulties that exist in extracting and visualizing scientific insights from these complex datasets. Using multidimensional band‐excitation scanning probe spectroscopy and adapting tools from both computer vision and machine learning, an automated workflow is developed to featurize, detect, and classify signatures of ferroelectric/ferroelastic switching processes in complex ferroelectric domain structures. This approach enables the identification and nanoscale visualization of varied modes of response and a pathway to statistically meaningful quantification of the differences between those modes. Among other things, the importance of domain geometry is spatially visualized for enhancing nanoscale electromechanical energy conversion.}, number={28}, journal={Advanced Materials}, author={Agar, J. C. and Cao, Y. and Naul, B. and Pandya, S. and Walt, S. and Luo, A. I. and Maher, J. T. and Balke, N. and Jesse, S. and Kalinin, S. V. and et al.}, year={2018} }
 @article{sharma_balachandran_sohn_krogel_ganesh_collins_ievlev_li_gao_balke_et al._2018, title={Nanoscale Control of Oxygen Defects and Metal-Insulator Transition in Epitaxial Vanadium Dioxides}, volume={12}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000440505000081&KeyUID=WOS:000440505000081}, DOI={10.1021/acsnano.8b03031}, abstractNote={Strongly correlated vanadium dioxide (VO2) is one of the most promising materials that exhibits a temperature-driven, metal-insulator transition (MIT) near room temperature. The ability to manipulate the MIT at nanoscale offers both insight into understanding the energetics of phase transition and a promising potential for nanoelectronic devices. In this work, we study nanoscale electrochemical modifications of the MIT in epitaxial VO2 thin films using a combined approach with scanning probe microscopy (SPM) and theoretical calculations. We find that applying electric voltages of different polarity through an SPM tip locally changes the contact potential difference and conductivity on the surface of VO2 by modulating the oxygen stoichiometry. We observed nearly 2 orders of magnitude change in resistance between positive and negative biased-tip written areas of the film, demonstrating the electric field modulated MIT behavior at the nanoscale. Density functional theory calculations, benchmarked against more accurate many-body quantum Monte Carlo calculations, provide information on the formation energetics of oxygen defects that can be further manipulated by strain. This study highlights the crucial role of oxygen vacancies in controlling the MIT in epitaxial VO2 thin films, useful for developing advanced electronic and iontronic devices.}, number={7}, journal={Acs Nano}, publisher={American Chemical Society (ACS)}, author={Sharma, Yogesh and Balachandran, Janakiraman and Sohn, Changhee and Krogel, Jaron T. and Ganesh, Panchapakesan and Collins, Liam and Ievlev, Anton V. and Li, Qian and Gao, Xiang and Balke, Nina and et al.}, year={2018}, pages={7159–7166} }
 @article{wang_mitchell_gao_tsai_boyd_pharr_balke_augustyn_2018, title={Operando Atomic Force Microscopy Reveals Mechanics of Structural Water Driven Battery-to-Pseudocapacitor Transition}, volume={12}, ISSN={["1936-086X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000436910200101&KeyUID=WOS:000436910200101}, DOI={10.1021/acsnano.8b02273}, abstractNote={The presence of structural water in tungsten oxides leads to a transition in the energy storage mechanism from battery-type intercalation (limited by solid state diffusion) to pseudocapacitance (limited by surface kinetics). Here, we demonstrate that these electrochemical mechanisms are linked to the mechanical response of the materials during intercalation of protons and present a pathway to utilize the mechanical coupling for local studies of electrochemistry. Operando atomic force microscopy dilatometry is used to measure the deformation of redox-active energy storage materials and to link the local nanoscale deformation to the electrochemical redox process. This technique reveals that the local mechanical deformation of the hydrated tungsten oxide is smaller and more gradual than the anhydrous oxide and occurs without hysteresis during the intercalation and deintercalation processes. The ability of layered materials with confined structural water to minimize mechanical deformation likely contributes to their fast energy storage kinetics.}, number={6}, journal={ACS NANO}, publisher={American Chemical Society (ACS)}, author={Wang, Ruocun and Mitchell, James B. and Gao, Qiang and Tsai, Wan-Yu and Boyd, Shelby and Pharr, Matt and Balke, Nina and Augustyn, Veronica}, year={2018}, month={Jun}, pages={6032–6039} }
 @article{zhao_bi_balke_rack_ward_kalinin_dai_feng_2018, title={Understanding Electric Double-Layer Gating Based on Ionic Liquids: from Nanoscale to Macroscale}, volume={10}, url={https://doi.org/10.1021/acsami.8b15199}, DOI={10.1021/acsami.8b15199}, abstractNote={In electric double-layer transistors (EDLTs), it is well known that the EDL formed by ionic liquids (ILs) can induce an ultrahigh carrier density at the semiconductor surface, compared to solid dielectric. However, the mechanism of device performance is still not fully understood, especially at a molecular level. Here, we evaluate the gating performance of amorphous indium gallium zinc oxide (a-IGZO) transistor coupled with a series of imidazolium-based ILs, using an approach combining of molecular dynamics simulation and finite element modeling. Results reveal that the EDL with different ion structures could produce inhomogeneous electric fields at the solid-electrolyte interface, and the heterogeneity of electric field-induced charge distributions at semiconductor surface could reduce the electrical conductance of a-IGZO during gating process. Meanwhile, a resistance network analysis was adopted to bridge the nanoscopic data with the macroscopic transfer characteristics of IL-gated transistor, and showed that our theoretical results could well estimate the gating performance of practical devices. Thereby, our findings could provide both new concepts and modeling techniques for IL-gated transistors.}, number={49}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Zhao, Wei and Bi, Sheng and Balke, Nina and Rack, Philip D. and Ward, Thomas Zac and Kalinin, Sergei V. and Dai, Sheng and Feng, Guang}, year={2018}, month={Dec}, pages={43211–43218} }
 @article{kim_hou_park_bahn_hoffman_black_bhattacharya_balke_hong_kim_et al._2017, title={Effect of defects on reaction of NiO surface with Pb-contained solution}, volume={7}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000397178100001&KeyUID=WOS:000397178100001}, DOI={10.1038/srep44805}, abstractNote={AbstractIn order to understand the role of defects in chemical reactions, we used two types of samples, which are molecular beam epitaxy (MBE) grown NiO(001) film on Mg(001) substrate as the defect free NiO prototype and NiO grown on Ni(110) single crystal as the one with defects. In-situ observations for oxide-liquid interfacial structure and surface morphology were performed for both samples in water and Pb-contained solution using high-resolution X-ray reflectivity and atomic force microscopy. For the MBE grown NiO, no significant changes were detected in the high-resolution X-ray reflectivity data with monotonic increase in roughness. Meanwhile, in the case of native grown NiO on Ni(110), significant changes in both the morphology and atomistic structure at the interface were observed when immersed in water and Pb-contained solution. Our results provide simple and direct experimental evidence of the role of the defects in chemical reaction of oxide surfaces with both water and Pb-contained solution.}, journal={Scientific Reports}, author={Kim, J. and Hou, B. Y. and Park, C. and Bahn, C. B. and Hoffman, J. and Black, J. and Bhattacharya, A. and Balke, N. and Hong, H. and Kim, J. H. and et al.}, year={2017} }
 @article{balabajew_balke_bazant_bennewitz_brilliantov_wijn_dey_drummond_dryfe_girault_et al._2017, title={Electroactuators: from understanding to micro-robotics and energy conversion: general discussion}, volume={199}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000405429100027&KeyUID=WOS:000405429100027}, DOI={10.1039/c7fd90031g}, abstractNote={Tom Kru-penkin: Where was the counter-electrode located in your “ bubbler ” device? If it was at the edge, is this not a problem for the upscaling? Tom Krupenkin responded: The location of the counter electrode is mostly a design choice. Since the bubbler cavity is  lled with a high conductivity liquid, most commonly a liquid metal, the exact counter electrode location is not really important, provided it is not far removed from the bubble array. One of the most obvious choices for the location is the plate at the top of the cavity, where the gas escape membrane is located. Nikolay Brilliantov asked: In your analysis of the energy balance in the system you do not explicitly take into account dissipation losses, which may be signi  - cant at high frequencies. Have you made the according estimates of the viscous losses?}, journal={Faraday Discussions}, author={Balabajew, M. and Balke, N. and Bazant, M. and Bennewitz, R. and Brilliantov, N. and Wijn, A. S. and Dey, R. and Drummond, C. and Dryfe, R. and Girault, H. and et al.}, year={2017}, pages={525–545} }
 @article{vasudevan_balke_maksymovych_jesse_kalinin_2017, title={Ferroelectric or non-ferroelectric: Why so many materials exhibit "ferroelectricity" on the nanoscale}, volume={4}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000402488200006&KeyUID=WOS:000402488200006}, DOI={10.1063/1.4979015}, abstractNote={Ferroelectric materials have remained one of the major focal points of condensed matter physics and materials science for over 50 years. In the last 20 years, the development of voltage-modulated scanning probe microscopy techniques, exemplified by Piezoresponse force microscopy (PFM) and associated time- and voltage spectroscopies, opened a pathway to explore these materials on a single-digit nanometer level. Consequently, domain structures and walls and polarization dynamics can now be imaged in real space. More generally, PFM has allowed studying electromechanical coupling in a broad variety of materials ranging from ionics to biological systems. It can also be anticipated that the recent Nobel prize [“The Nobel Prize in Chemistry 2016,” http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/ (Nobel Media, 2016)] in molecular electromechanical machines will result in rapid growth in interest in PFM as a method to probe their behavior on single device and device assembly levels. However, the broad introduction of PFM also resulted in a growing number of reports on the nearly ubiquitous presence of ferroelectric-like phenomena including remnant polar states and electromechanical hysteresis loops in materials which are non-ferroelectric in the bulk or in cases where size effects are expected to suppress ferroelectricity. While in certain cases plausible physical mechanisms can be suggested, there is remarkable similarity in observed behaviors, irrespective of the materials system. In this review, we summarize the basic principles of PFM, briefly discuss the features of ferroelectric surfaces salient to PFM imaging and spectroscopy, and summarize existing reports on ferroelectric-like responses in non-classical ferroelectric materials. We further discuss possible mechanisms behind observed behaviors and possible experimental strategies for their identification.}, number={2}, journal={Applied Physics Reviews}, publisher={AIP Publishing}, author={Vasudevan, Rama K. and Balke, Nina and Maksymovych, Peter and Jesse, Stephen and Kalinin, Sergei V.}, year={2017}, pages={021302} }
 @article{wong_noh_pudasaini_wolf_balke_herklotz_sharma_haglund_dai_mandrus_et al._2017, title={Impact of gate geometry on ionic liquid gated ionotronic systems}, volume={5}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000400350900006&KeyUID=WOS:000400350900006}, DOI={10.1063/1.4974485}, abstractNote={Ionic liquid electrolytes are gaining widespread application as a gate dielectric used to control ion transport in functional materials. This letter systematically examines the important influence that device geometry in standard “side gate” 3-terminal geometries plays in device performance of a well-known oxygen ion conductor. We show that the most influential component of device design is the ratio between the area of the gate electrode and the active channel, while the spacing between these components and their individual shapes has a negligible contribution. These findings provide much needed guidance in device design intended for ionotronic gating with ionic liquids.}, number={4}, journal={Apl Materials}, author={Wong, A. T. and Noh, J. H. and Pudasaini, P. R. and Wolf, B. and Balke, N. and Herklotz, A. and Sharma, Y. and Haglund, A. V. and Dai, S. and Mandrus, D. and et al.}, year={2017} }
 @article{balke_ramesh_yu_2017, title={Manipulating Ferroelectrics through Changes in Surface and Interface Properties}, volume={9}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000416203800067&KeyUID=WOS:000416203800067}, DOI={10.1021/acsami.7b10747}, abstractNote={Ferroelectric materials are used in many applications of modern technologies including information storage, transducers, sensors, tunable capacitors, and other novel device concepts. In many of these applications, the ferroelectric properties, such as switching voltages, piezoelectric constants, or stability of nanodomains, are crucial. For any application, even for material characterization, the material itself needs to be interfaced with electrodes. On the basis of the structural, chemical, and electronic properties of the interfaces, the measured material properties can be determined by the interface. This is also true for surfaces. However, the importance of interfaces and surfaces and their effect on experiments are often neglected, which results in many dramatically different experimental results for nominally identical samples. Therefore, it is crucial to understand the role of the interface and surface properties on internal bias fields and the domain switching process. Here, the nanoscale ferroelectric switching process and the stability of nanodomains for Pb(Zr,Ti)O3 thin films are investigated by using scanning probe microscopy. Interface and surface properties are modulated through the selection/redesign of electrode materials as well as tuning the surface-near oxygen vacancies, which both can result in changes of the electric fields acting across the sample, and consequently this controls the measured ferroelectric and domain retention properties. By understanding the role of surfaces and interfaces, ferroelectric properties can be tuned to eliminate the problem of asymmetric domain stability by combining the effects of different electrode materials. This study forms an important step toward integrating ferroelectric materials in electronic devices.}, number={45}, journal={Acs Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Balke, Nina and Ramesh, Ramamoorthy and Yu, Pu}, year={2017}, pages={39736–39746} }
 @article{yang_morozovska_kumar_eliseev_cao_mazet_balke_jesse_vasudevan_dubourdieu_et al._2017, title={Mixed electrochemical-ferroelectric states in nanoscale ferroelectrics}, volume={13}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000406778100023&KeyUID=WOS:000406778100023}, DOI={10.1038/nphys4103}, abstractNote={Ferroelectricity on the nanoscale has been the subject of much fascination in condensed-matter physics for over half a century. In recent years, multiple reports claiming ferroelectricity in ultrathin ferroelectric films based on the formation of remnant polarization states, local electromechanical hysteresis loops, and pressure-induced switching were made. However, similar phenomena were reported for traditionally non-ferroelectric materials, creating a significant level of uncertainty in the field. Here we show that in nanoscale systems the ferroelectric state is fundamentally inseparable from the electrochemical state of the surface, leading to the emergence of a mixed electrochemical–ferroelectric state. We explore the nature, thermodynamics, and thickness evolution of such states, and demonstrate the experimental pathway to establish its presence. This analysis reconciles multiple prior studies, provides guidelines for studies of ferroelectric materials on the nanoscale, and establishes the design paradigm for new generations of ferroelectric-based devices. Nanoscale ferroelectricity is hard to characterize. Studies of BaTiO3 thin films now reveal a close coupling between the ferroelectric and the surface electrochemical states — a notion important for future applications of ferroelectric nanomaterials.}, number={8}, journal={Nature Physics}, author={Yang, S. M. and Morozovska, A. N. and Kumar, R. and Eliseev, E. A. and Cao, Y. and Mazet, L. and Balke, N. and Jesse, S. and Vasudevan, R. K. and Dubourdieu, C. and et al.}, year={2017}, pages={812-+} }
 @article{black_come_bi_zhu_zhao_wong_noh_pudasaini_zhang_okatan_et al._2017, title={Role of Electrical Double Layer Structure in Ionic Liquid Gated Devices}, volume={9}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000416614600118&KeyUID=WOS:000416614600118}, DOI={10.1021/acsami.7b11044}, abstractNote={Ionic liquid gating of transition metal oxides has enabled new states (magnetic, electronic, metal-insulator), providing fundamental insights into the physics of strongly correlated oxides. However, despite much research activity, little is known about the correlation of the structure of the liquids in contact with the transition metal oxide surface, its evolution with the applied electric potential, and its correlation with the measured electronic properties of the oxide. Here, we investigate the structure of an ionic liquid at a semiconducting oxide interface during the operation of a thin film transistor where the electrical double layer gates the device using experiment and theory. We show that the transition between the ON and OFF states of the amorphous indium gallium zinc oxide transistor is accompanied by a densification and preferential spatial orientation of counterions at the oxide channel surface. This process occurs in three distinct steps, corresponding to ion orientations, and consequently, regimes of different electrical conductivity. The reason for this can be found in the surface charge densities on the oxide surface when different ion arrangements are present. Overall, the field-effect gating process is elucidated in terms of the interfacial ionic liquid structure, and this provides unprecedented insight into the working of a liquid gated transistor linking the nanoscopic structure to the functional properties. This knowledge will enable both new ionic liquid design as well as advanced device concepts.}, number={46}, journal={Acs Applied Materials & Interfaces}, author={Black, J. M. and Come, J. and Bi, S. and Zhu, M. Y. and Zhao, W. and Wong, A. T. and Noh, J. H. and Pudasaini, P. R. and Zhang, P. F. and Okatan, M. B. and et al.}, year={2017}, pages={40949–40958} }
 @article{gao_come_naguib_jesse_gogotsi_balke_2017, title={Synergetic effects of K+ and Mg2+ ion intercalation on the electrochemical and actuation properties of the two-dimensional Ti3C2 MXene}, volume={199}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000405429100021&KeyUID=WOS:000405429100021}, DOI={10.1039/c6fd00251j}, abstractNote={Two-dimensional materials, such as MXenes, are attractive candidates for energy storage and electrochemical actuators due to their high volume changes upon ion intercalation. Of special interest for boosting energy storage is the intercalation of multivalent ions such as Mg2+, which suffers from sluggish intercalation and transport kinetics due to its ion size. By combining traditional electrochemical characterization techniques with electrochemical dilatometry and contact resonance atomic force microscopy, the synergetic effects of the pre-intercalation of K+ions are demonstrated to improve the charge storage of multivalent ions, as well as tune the mechanical and actuation properties of the Ti3C2MXene. Our results have important implications for quantitatively understanding the charge storage processes in intercalation compounds and provide a new path for studying the mechanical evolution of energy storage materials.}, journal={Faraday Discussions}, publisher={Royal Society of Chemistry (RSC)}, author={Gao, Qiang and Come, Jeremy and Naguib, Michael and Jesse, Stephen and Gogotsi, Yury and Balke, Nina}, year={2017}, pages={393–403} }
 @article{damodaran_pandya_agar_cao_vasudevan_xu_saremi_li_kim_mccarter_et al._2017, title={Three-State Ferroelastic Switching and Large Electromechanical Responses in PbTiO3 Thin Films}, volume={29}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000412184100007&KeyUID=WOS:000412184100007}, DOI={10.1002/adma.201702069}, abstractNote={Leveraging competition between energetically degenerate states to achieve large field‐driven responses is a hallmark of functional materials, but routes to such competition are limited. Here, a new route to such effects involving domain‐structure competition is demonstrated, which arises from strain‐induced spontaneous partitioning of PbTiO3 thin films into nearly energetically degenerate, hierarchical domain architectures of coexisting c/a and a1/a2 domain structures. Using band‐excitation piezoresponse force microscopy, this study manipulates and acoustically detects a facile interconversion of different ferroelastic variants via a two‐step, three‐state ferroelastic switching process (out‐of‐plane polarized c+ → in‐plane polarized a → out‐of‐plane polarized c− state), which is concomitant with large nonvolatile electromechanical strains (≈1.25%) and tunability of the local piezoresponse and elastic modulus (>23%). It is further demonstrated that deterministic, nonvolatile writing/erasure of large‐area patterns of this electromechanical response is possible, thus showing a new pathway to improved function and properties.}, number={37}, journal={Advanced Materials}, author={Damodaran, A.R. and Pandya, S. and Agar, J.C. and Cao, Y. and Vasudevan, R. and Xu, R. and Saremi, S. and Li, Q. and Kim, J. and McCarter, M.R. and et al.}, year={2017}, month={Oct}, pages={1702069} }
 @article{weinrich_come_tempel_kungl_eichel_balke_2017, title={Understanding the nanoscale redox-behavior of iron-anodes for rechargeable iron-air batteries}, volume={41}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000415302600078&KeyUID=WOS:000415302600078}, DOI={10.1016/j.nanoen.2017.10.023}, abstractNote={Iron-air cells provide a promising and resource-efficient alternative battery concept with superior area specific power density characteristics compared to state-of-the-art Li-air batteries and potentially superior energy density characteristics compared to present Li-ion batteries. Understanding charge-transfer reactions at the anode-electrolyte interface is the key to develop high-performance cells. By employing in-situ electrochemical atomic force microscopy (in-situ EC-AFM), in-depth insight into the electrochemically induced surface reaction processes on iron in concentrated alkaline electrolyte is obtained. The results highlight the formation and growth of the redox-layer on iron over the course of several oxidation/reduction cycles. By this means, a direct correlation between topography changes and the corresponding electrochemical reactions at the nanoscale could unambiguously be established. Here, the twofold character of the nanoparticulate redox-layer in terms of its passivating character and its contribution to the electrochemical reactions is elucidated. Furthermore, the evolution of single nanoparticles on the iron electrode surface is evaluated in unprecedented and artifact-free detail. Based on the dedicated topography analysis, a detailed structural model for the evolution of the redox-layer which is likewise elementary for corrosion science and battery research is derived.}, journal={Nano Energy}, author={Weinrich, H. and Come, J. and Tempel, H. and Kungl, H. and Eichel, R. A. and Balke, N.}, year={2017}, pages={706–716} }
 @article{verde_baggetto_balke_veith_seo_wang_meng_2016, title={Elucidating the Phase Transformation of Li4Ti5O12 Lithiation at the Nanoscale}, volume={10}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000375245000049&KeyUID=WOS:000375245000049}, DOI={10.1021/acsnano.5b07875}, abstractNote={This work provides insight regarding the fundamental lithiation and delithiation mechanism of the popular lithium ion battery anode material, Li4Ti5O12 (LTO). Our results quantify the extent of reaction between Li4Ti5O12 and Li7Ti5O12 at the nanoscale, during the first cycle. Lithium titanate's discharge (lithiation) and charge (delithiation) reactions are notoriously difficult to characterize due to the zero-strain transition occurring between the end members Li4Ti5O12 and Li7Ti5O12. Interestingly, however, the latter compound is electronically conductive, while the former is an insulator. We take advantage of this critical property difference by using conductive atomic force microscopy (c-AFM) to locally monitor the phase transition between the two structures at various states of charge. To do so, we perform ex situ characterization on electrochemically cycled LTO thin-films that are never exposed to air. We provide direct confirmation of the manner in which the reaction occurs, which proceeds via percolation channels within single grains. We complement scanning probe analyses with an X-ray photoelectron spectroscopy (XPS) study that identifies and explains changes in the LTO surface structure and composition. In addition, we provide a computational analysis to describe the unique electronic differences between LTO and its lithiated form.}, number={4}, journal={Acs Nano}, author={Verde, M. G. and Baggetto, L. and Balke, N. and Veith, G. M. and Seo, J. K. and Wang, Z. Y. and Meng, Y. S.}, year={2016}, pages={4312–4321} }
 @article{meyer_herklotz_lauter_freeland_nichols_guo_lee_ward_balke_kalinin_et al._2016, title={Enhancing interfacial magnetization with a ferroelectric}, volume={94}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000388464100005&KeyUID=WOS:000388464100005}, DOI={10.1103/PhysRevB.94.174432}, abstractNote={Ferroelectric control of the electronic and magnetic properties of a correlated oxide provides new opportunities for fundamental science and practical device applications. However, the exploding interest in ferroelectric control of magnetic interfaces, which typically happens in a few nanometers, has been inhibited by the lack of appropriate characterization techniques. Here, the authors have used polarized neutron reflectivity (PNR), a nondestructive yet powerful technique, to directly probe the evolution of the interfacial magnetism at the interface between ferromagnetic La${}_{0.8}$Sr${}_{0.2}$MnO${}_{3}$ and ferroelectric PbZr${}_{0.2}$Ti${}_{0.8}$O${}_{3}$. Using PNR, the authors find that the orientation of the ferroelectric polarization of the ferroelectric layer critically determines the interfacial magnetism, which occurs within a few nanometers of the interface. When the polarization is oriented towards the manganite layer, it is capable of enhancing the interfacial magnetization above the bulk region of the film. This finding not only proves the ferroelectric field effect control of magnetism, but also emphasizes the necessity of separating bulk properties from interfacial phenomena in magnetoelectric materials.}, number={17}, journal={Physical Review B}, author={Meyer, T. L. and Herklotz, A. and Lauter, V. and Freeland, J. W. and Nichols, J. and Guo, E. J. and Lee, S. and Ward, T. Z. and Balke, N. and Kalinin, S. V. and et al.}, year={2016} }
 @article{cao_yang_jesse_kravchenko_yu_chen_kalinin_balke_li_2016, title={Exploring Polarization Rotation Instabilities in Super-Tetragonal BiFeO3 Epitaxial Thin Films and Their Technological Implications}, volume={2}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000392939300009&KeyUID=WOS:000392939300009}, DOI={10.1002/aelm.201600307}, abstractNote={Dr. Y. Cao, Dr. S. Jesse, Dr. I. Kravchenko, Dr. S. V. Kalinin, Dr. N. Balke, Dr. Q. Li Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge, TN 37831, USA E-mail: balken@ornl.gov; liq1@ornl.gov S. Yang, Prof. P. Yu State Key Laboratory for Low-Dimensional Quantum Physics Department of Physics and Collaborative Innovation Center for Quantum Matter Tsinghua University Beijing 100084, China S. Yang, Prof. P. Yu RIKEN Center for Emergent Matter Science (CEMS) Wako, Saitama 351-0198, Japan Prof. L.-Q. Chen Department of Materials Science and Engineering The Pennsylvania State University University Park, PA 16802, USA}, number={12}, journal={Advanced Electronic Materials}, author={Cao, Y. and Yang, S. Z. and Jesse, S. and Kravchenko, I. and Yu, P. and Chen, L. Q. and Kalinin, S. V. and Balke, N. and Li, Q.}, year={2016} }
 @article{beekman_siemons_chi_balke_howe_ward_maksymovych_budai_tischler_xu_et al._2016, title={Ferroelectric Self-Poling, Switching, and Monoclinic Domain Configuration in BiFeO3 Thin Films}, volume={26}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000380890200019&KeyUID=WOS:000380890200019}, DOI={10.1002/adfm.201600468}, abstractNote={Self‐poling of ferroelectric films, i.e., a preferred, uniform direction of the ferroelectric polarization in as‐grown samples is often observed yet poorly understood despite its importance for device applications. The multiferroic perovskite BiFeO3, which crystallizes in two distinct structural polymorphs depending on applied epitaxial strain, is well known to exhibit self‐poling. This study investigates the effect of self‐poling on the monoclinic domain configuration and the switching properties of the two polymorphs of BiFeO3 (R′ and T′) in thin films grown on LaAlO3 substrates with slightly different La0.3Sr0.7MnO3 buffer layers. This study shows that the polarization state formed during the growth acts as “imprint” on the polarization and that switching the polarization away from this self‐poled direction can only be done at the expense of the sample's monoclinic domain configuration. The observed reduction of the monoclinic domain size is largely reversible; hence, the domain size is restored when the polarization is switched back to its original orientation. This is a direct consequence of the growth taking place in the polar phase (below Tc). Switching the polarization away from the preferred configuration, in which defects and domain patterns synergistically minimize the system's energy, leads to a domain state with smaller (and more highly strained and distorted) monoclinic domains.}, number={28}, journal={Advanced Functional Materials}, author={Beekman, C. and Siemons, W. and Chi, M. and Balke, N. and Howe, J. Y. and Ward, T. Z. and Maksymovych, P. and Budai, J. D. and Tischler, J. Z. and Xu, R. and et al.}, year={2016}, pages={5166–5173} }
 @article{collins_belianinov_somnath_balke_kalinin_jesse_2016, title={Full data acquisition in Kelvin Probe Force Microscopy: Mapping dynamic electric phenomena in real space}, volume={6}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000381262700001&KeyUID=WOS:000381262700001}, DOI={10.1038/srep30557}, abstractNote={AbstractKelvin probe force microscopy (KPFM) has provided deep insights into the local electronic, ionic and electrochemical functionalities in a broad range of materials and devices. In classical KPFM, which utilizes heterodyne detection and closed loop bias feedback, the cantilever response is down-sampled to a single measurement of the contact potential difference (CPD) per pixel. This level of detail, however, is insufficient for materials and devices involving bias and time dependent electrochemical events; or at solid-liquid interfaces, where non-linear or lossy dielectrics are present. Here, we demonstrate direct recovery of the bias dependence of the electrostatic force at high temporal resolution using General acquisition Mode (G-Mode) KPFM. G-Mode KPFM utilizes high speed detection, compression and storage of the raw cantilever deflection signal in its entirety at high sampling rates. We show how G-Mode KPFM can be used to capture nanoscale CPD and capacitance information with a temporal resolution much faster than the cantilever bandwidth, determined by the modulation frequency of the AC voltage. In this way, G-Mode KPFM offers a new paradigm to study dynamic electric phenomena in electroactive interfaces as well as a promising route to extend KPFM to the solid-liquid interface.}, journal={Scientific Reports}, author={Collins, L. and Belianinov, A. and Somnath, S. and Balke, N. and Kalinin, S. V. and Jesse, S.}, year={2016} }
 @article{black_zhu_zhang_unocic_guo_okatan_dai_cummings_kalinin_feng_et al._2016, title={Fundamental aspects of electric double layer force-distance measurements at liquid-solid interfaces using atomic force microscopy}, volume={6}, ISSN={2045-2322}, url={http://dx.doi.org/10.1038/srep32389}, DOI={10.1038/srep32389}, abstractNote={AbstractAtomic force microscopy (AFM) force-distance measurements are used to investigate the layered ion structure of Ionic Liquids (ILs) at the mica surface. The effects of various tip properties on the measured force profiles are examined and reveal that the measured ion position is independent of tip properties, while the tip radius affects the forces required to break through the ion layers as well as the adhesion force. Force data is collected for different ILs and directly compared with interfacial ion density profiles predicted by molecular dynamics. Through this comparison it is concluded that AFM force measurements are sensitive to the position of the ion with the larger volume and mass, suggesting that ion selectivity in force-distance measurements are related to excluded volume effects and not to electrostatic or chemical interactions between ions and AFM tip. The comparison also revealed that at distances greater than 1 nm the system maintains overall electroneutrality between the AFM tip and sample, while at smaller distances other forces (e.g., van der waals interactions) dominate and electroneutrality is no longer maintained.}, number={1}, journal={Scientific Reports}, publisher={Springer Science and Business Media LLC}, author={Black, Jennifer M. and Zhu, Mengyang and Zhang, Pengfei and Unocic, Raymond R. and Guo, Daqiang and Okatan, M. Baris and Dai, Sheng and Cummings, Peter T. and Kalinin, Sergei V. and Feng, Guang and et al.}, year={2016}, month={Sep} }
 @article{agar_damodaran_okatan_kacher_gammer_vasudevan_pandya_dedon_mangalam_velarde_et al._2016, title={Highly mobile ferroelastic domain walls in compositionally graded ferroelectric thin films}, volume={15}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000374763500018&KeyUID=WOS:000374763500018}, DOI={10.1038/nmat4567}, abstractNote={Domains and domain walls are critical in determining the response of ferroelectrics, and the ability to controllably create, annihilate, or move domains is essential to enable a range of next-generation devices. Whereas electric-field control has been demonstrated for ferroelectric 180° domain walls, similar control of ferroelastic domains has not been achieved. Here, using controlled composition and strain gradients, we demonstrate deterministic control of ferroelastic domains that are rendered highly mobile in a controlled and reversible manner. Through a combination of thin-film growth, transmission-electron-microscopy-based nanobeam diffraction and nanoscale band-excitation switching spectroscopy, we show that strain gradients in compositionally graded PbZr1-xTixO3 heterostructures stabilize needle-like ferroelastic domains that terminate inside the film. These needle-like domains are highly labile in the out-of-plane direction under applied electric fields, producing a locally enhanced piezoresponse. This work demonstrates the efficacy of novel modes of epitaxy in providing new modalities of domain engineering and potential for as-yet-unrealized nanoscale functional devices.}, number={5}, journal={Nature Materials}, author={Agar, J. C. and Damodaran, A. R. and Okatan, M. B. and Kacher, J. and Gammer, C. and Vasudevan, R. K. and Pandya, S. and Dedon, L. R. and Mangalam, R. V. K. and Velarde, G. A. and et al.}, year={2016}, pages={549-+} }
 @article{collins_belianinov_somnath_rodriguez_balke_kalinin_jesse_2016, title={Multifrequency spectrum analysis using fully digital G Mode-Kelvin probe force microscopy}, volume={27}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000369849200018&KeyUID=WOS:000369849200018}, DOI={10.1088/0957-4484/27/10/105706}, abstractNote={Since its inception over two decades ago, Kelvin probe force microscopy (KPFM) has become the standard technique for characterizing electrostatic, electrochemical and electronic properties at the nanoscale. In this work, we present a purely digital, software-based approach to KPFM utilizing big data acquisition and analysis methods. General mode (G-Mode) KPFM works by capturing the entire photodetector data stream, typically at the sampling rate limit, followed by subsequent de-noising, analysis and compression of the cantilever response. We demonstrate that the G-Mode approach allows simultaneous multi-harmonic detection, combined with on-the-fly transfer function correction—required for quantitative CPD mapping. The KPFM approach outlined in this work significantly simplifies the technique by avoiding cumbersome instrumentation optimization steps (i.e. lock in parameters, feedback gains etc), while also retaining the flexibility to be implemented on any atomic force microscopy platform. We demonstrate the added advantages of G-Mode KPFM by allowing simultaneous mapping of CPD and capacitance gradient (C′) channels as well as increased flexibility in data exploration across frequency, time, space, and noise domains. G-Mode KPFM is particularly suitable for characterizing voltage sensitive materials or for operation in conductive electrolytes, and will be useful for probing electrodynamics in photovoltaics, liquids and ionic conductors.}, number={10}, journal={Nanotechnology}, author={Collins, L. and Belianinov, A. and Somnath, S. and Rodriguez, B. J. and Balke, N. and Kalinin, S. V. and Jesse, S.}, year={2016} }
 @article{come_xie_naguib_jesse_kalinin_gogotsi_kent_balke_2016, title={Nanoscale Elastic Changes in 2D Ti3C2Tx (MXene) Pseudocapacitive Electrodes}, volume={6}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000379306400012&KeyUID=WOS:000379306400012}, DOI={10.1002/aenm.201502290}, abstractNote={Designing sustainable electrodes for next generation energy storage devices relies on the understanding of their fundamental properties at the nanoscale, including the comprehension of ions insertion into the electrode and their interactions with the active material. One consequence of ion storage is the change in the electrode volume resulting in mechanical strain and stress that can strongly affect the cycle life. Therefore, it is important to understand the changes of dimensions and mechanical properties occurring during electrochemical reactions. While the characterization of mechanical properties via macroscopic measurements is well documented, in situ characterization of their evolution has never been achieved at the nanoscale. It is reported here with in situ imaging, combined with density functional theory of the elastic changes of a 2D titanium carbide (Ti3C2Tx) based electrode in direction normal to the basal plane (electrode surface) during alkaline cation intercalation/extraction. 2D carbides, known as MXenes, are promising new materials for supercapacitors and various kinds of batteries, and understanding the coupling between their mechanical and electrochemical properties is therefore necessary. The results show a strong correlation between the cations content and the out‐of‐plane elastic modulus. This strategy enables identifying the preferential intercalation pathways within a single particle, which is important for understanding ionic transport in these materials.}, number={9}, journal={Advanced Energy Materials}, author={Come, J. and Xie, Y. and Naguib, M. and Jesse, S. and Kalinin, S. V. and Gogotsi, Y. and Kent, P. R. C. and Balke, N.}, year={2016} }
 @article{balke_jesse_carmichael_okatan_kravchenko_kalinin_tselev_2017, title={Quantification of in-contact probe-sample electrostatic forces with dynamic atomic force microscopy}, volume={28}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000392217400001&KeyUID=WOS:000392217400001}, DOI={10.1088/1361-6528/aa5370}, abstractNote={Atomic Force Microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. In combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V/nm at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.}, number={6}, journal={Nanotechnology}, author={Balke, N. and Jesse, S. and Carmichael, B. and Okatan, M. B. and Kravchenko, II and Kalinin, S. V. and Tselev, A.}, year={2017} }
 @article{balke_jesse_yu_carmichael_kalinin_tselev_2016, title={Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopy}, volume={27}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000385483900006&KeyUID=WOS:000385483900006}, DOI={10.1088/0957-4484/27/42/425707}, abstractNote={Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ∼1–3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip–sample contact stiffness. The approach has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. This analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.}, number={42}, journal={Nanotechnology}, author={Balke, N. and Jesse, S. and Yu, P. and Carmichael, B. and Kalinin, S. V. and Tselev, A.}, year={2016} }
 @article{chyasnavichyus_susner_ievlev_eliseev_kalinin_balke_morozovska_mcguire_maksymovych_2016, title={Size-effect in layered ferrielectric CuInP2S6}, volume={109}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000387258300025&KeyUID=WOS:000387258300025}, DOI={10.1063/1.4965837}, abstractNote={We report on polarization switching properties of thin flakes of van der Waals ferrielectric CuInP2S6. We observe mesoscale polarization domains, ferroelectric switching, and the Curie temperature above 299 K down to a thickness of ∼50 nm. However, the electromechanical response is progressively suppressed below 50 nm, and vanishes at room temperature at a thickness of ∼10 nm. Though larger than a single layer, 10 nm is still a very small value compared to the expectations for an intrinsic ferroelectric semiconductor. We therefore propose a model for a doped surface layer that screens spontaneous polarization in this material. The charges in the screening layer may also participate in secondary chemical reactions, which may explain domain pinning observed in thermal cycling of the flakes above the Curie temperature. At the same time, ferroelectric switching is intertwined with ionic diffusion, resulting in erratic and damaging switching at room temperature. Owing to much stronger temperature dependence of ionic diffusion, the two phenomena can be decoupled allowing more reliable switching to be obtained at low temperatures.}, number={17}, journal={Applied Physics Letters}, author={Chyasnavichyus, M. and Susner, M. A. and Ievlev, A. V. and Eliseev, E. A. and Kalinin, S. V. and Balke, N. and Morozovska, A. N. and McGuire, M. A. and Maksymovych, P.}, year={2016} }
 @article{strelcov_yang_jesse_balke_vasudevan_kalinin_2016, title={Solid-state electrochemistry on the nanometer and atomic scales: the scanning probe microscopy approach}, volume={8}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=MEDLINE&KeyUT=MEDLINE:27146961&KeyUID=MEDLINE:27146961}, DOI={10.1039/c6nr01524g}, abstractNote={Energy technologies of the 21(st) century require an understanding and precise control over ion transport and electrochemistry at all length scales - from single atoms to macroscopic devices. This short review provides a summary of recent studies dedicated to methods of advanced scanning probe microscopy for probing electrochemical transformations in solids at the meso-, nano- and atomic scales. The discussion presents the advantages and limitations of several techniques and a wealth of examples highlighting peculiarities of nanoscale electrochemistry.}, number={29}, journal={Nanoscale}, author={Strelcov, Evgheni and Yang, Sang Mo and Jesse, Stephen and Balke, Nina and Vasudevan, Rama K. and Kalinin, Sergei V.}, year={2016}, pages={13838–58} }
 @article{collins_jesse_balke_rodriguez_kalinin_li_2015, title={Band excitation Kelvin probe force microscopy utilizing photothermal excitation}, volume={106}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000351397600072&KeyUID=WOS:000351397600072}, DOI={10.1063/1.4913910}, abstractNote={A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standard ambient KPFM approach, amplitude modulated KPFM. Finally, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.}, number={10}, journal={Applied Physics Letters}, author={Collins, Liam and Jesse, Stephen and Balke, Nina and Rodriguez, Brian J. and Kalinin, Sergei and Li, Qian}, year={2015} }
 @article{come_black_lukatskaya_naguib_beidaghi_rondinone_kalinin_wesolowski_gogotsi_balke_2015, title={Controlling the actuation properties of MXene paper electrodes upon cation intercalation}, volume={17}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000366149000004&KeyUID=WOS:000366149000004}, DOI={10.1016/j.nanoen.2015.07.028}, abstractNote={Atomic force microscopy was used to monitor the macroscopic deformation in a delaminated Ti3C2 paper electrode in situ, during charge/discharge in a variety of aqueous electrolytes to examine the effect of the cation intercalation on the electrochemical behavior and mechanical response. The results show a strong dependence of the electrode deformation on cation size and charge. The electrode undergoes a large contraction during Li+, Na+ or Mg2+ intercalation, differentiating the Ti3C2 paper from conventional electrodes where redox intercalation of ions (e.g. Li+) into the bulk phase (e.g. graphite, silicon) results in volumetric expansion. This feature may explain the excellent rate performance and cyclability reported for MXenes. We also demonstrated that the variation of the electromechanical contraction can be easily adjusted by electrolyte exchange, and shows interesting characteristics for the design of actuators based on 2D metal carbides.}, journal={Nano Energy}, author={Come, J. and Black, J. M. and Lukatskaya, M. R. and Naguib, M. and Beidaghi, M. and Rondinone, A. J. and Kalinin, S. V. and Wesolowski, D. J. and Gogotsi, Y. and Balke, N.}, year={2015}, pages={27–35} }
 @article{balke_jesse_li_maksymovych_okatan_strelcov_tselev_kalinin_2015, title={Current and surface charge modified hysteresis loops in ferroelectric thin films}, volume={118}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000360441900014&KeyUID=WOS:000360441900014}, DOI={10.1063/1.4927811}, abstractNote={Polarization domains in ferroelectric materials and the ability to orient them with an external electric field lead to the development of a variety of applications from information storage to actuation. The development of piezoresponse force microscopy (PFM) has enabled researchers to investigate ferroelectric domains and ferroelectric domain switching on the nanoscale, which offers a pathway to study structure-function relationships in this important material class. Due to its commercial availability and ease of use, PFM has become a widely used research tool. However, measurement artifacts, i.e., alternative signal origins besides the piezoelectric effect are barely discussed or considered. This becomes especially important for materials with a small piezoelectric coefficient or materials with unknown ferroelectric properties, including non-ferroelectric materials. Here, the role of surface charges and current flow during PFM measurements on classical ferroelectrics are discussed and it will be shown how they alter the PFM hysteresis loop shape. This will help to better address alternative signal origins in PFM-type experiments and offer a pathway to study additional phenomena besides ferroelectricity.}, number={7}, journal={Journal of Applied Physics}, author={Balke, Nina and Jesse, Stephen and Li, Qian and Maksymovych, Petro and Okatan, M. Baris and Strelcov, Evgheni and Tselev, Alexander and Kalinin, Sergei V.}, year={2015} }
 @article{balke_maksymovych_jesse_herklotz_tselev_eom_kravchenko_yu_kalinin_2015, title={Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects with Scanning Probe Microscopy}, volume={9}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000356988500091&KeyUID=WOS:000356988500091}, DOI={10.1021/acsnano.5b02227}, abstractNote={Ferroelectricity in functional materials remains one of the most fascinating areas of modern science in the past several decades. In the last several years, the rapid development of piezoresponse force microscopy (PFM) and spectroscopy revealed the presence of electromechanical hysteresis loops and bias-induced remnant polar states in a broad variety of materials including many inorganic oxides, polymers, and biosystems. In many cases, this behavior was interpreted as the ample evidence for ferroelectric nature of the system. Here, we systematically analyze PFM responses on ferroelectric and nonferroelectric materials and demonstrate that mechanisms unrelated to ferroelectricity can induce ferroelectric-like characteristics through charge injection and electrostatic forces on the tip. We will focus on similarities and differences in various PFM measurement characteristics to provide an experimental guideline to differentiate between ferroelectric material properties and charge injection. In the end, we apply the developed measurement protocols to an unknown ferroelectric material.}, number={6}, journal={Acs Nano}, author={Balke, Nina and Maksymovych, Petro and Jesse, Stephen and Herklotz, Andreas and Tselev, Alexander and Eom, Chang-Beom and Kravchenko, Ivan I. and Yu, Pu and Kalinin, Sergei V.}, year={2015}, pages={6484–6492} }
 @article{winchester_balke_cheng_morozovska_kalinin_chen_2015, title={Electroelastic fields in artificially created vortex cores in epitaxial BiFeO3 thin films}, volume={107}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000359375700024&KeyUID=WOS:000359375700024}, DOI={10.1063/1.4927750}, abstractNote={We employ phase-field modeling to explore the elastic properties of artificially created 1-D domain walls in (001)p-oriented BiFeO3 thin films, composed of a junction of the four polarization variants, all with the same out-of-plane polarization. It was found that these junctions exhibit peculiarly high electroelastic fields induced by the neighboring ferroelastic/ferroelectric domains. The vortex core exhibits a volume expansion, while the anti-vortex core is more compressive. Possible ways to control the electroelastic field, such as varying material constant and applying transverse electric field, are also discussed.}, number={5}, journal={Applied Physics Letters}, author={Winchester, B. and Balke, N. and Cheng, X. X. and Morozovska, A. N. and Kalinin, S. and Chen, L. Q.}, year={2015} }
 @article{li_cao_yu_vasudevan_laanait_tselev_xue_chen_maksymovych_kalinin_et al._2015, title={Giant elastic tunability in strained BiFeO3 near an electrically induced phase transition}, volume={6}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=MEDLINE&KeyUT=MEDLINE:26597483&KeyUID=MEDLINE:26597483}, DOI={10.1038/ncomms9985}, abstractNote={AbstractElastic anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation elastic/piezoresponse spectroscopy, we probed sub-MHz elastic dynamics of a tip bias-induced rhombohedral−tetragonal phase transition of strained (001)-BiFeO3 (rhombohedral) ferroelectric thin films from ∼103 nm3 sample volumes. Near this transition, we observed that the Young’s modulus intrinsically softens by over 30% coinciding with two- to three-fold enhancement of local piezoresponse. Coupled with phase-field modelling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (for example, domain walls) on the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary in ferroelectrics. Furthermore, the giant electrically tunable elastic stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO3 in next-generation frequency-agile electroacoustic devices, based on the utilization of the soft modes underlying successive ferroelectric phase transitions.}, journal={Nature communications}, author={Li, Q. and Cao, Y. and Yu, P. and Vasudevan, R. K. and Laanait, N. and Tselev, A. and Xue, F. and Chen, L. Q. and Maksymovych, P. and Kalinin, S. V. and et al.}, year={2015}, pages={8985} }
 @article{sacci_black_balke_dudney_more_unocic_2015, title={Nanoscale Imaging of Fundamental Li Battery Chemistry: Solid-Electrolyte Interphase Formation and Preferential Growth of Lithium Metal Nanoclusters}, volume={15}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl5048626}, DOI={10.1021/nl5048626}, abstractNote={The performance characteristics of Li-ion batteries are intrinsically linked to evolving nanoscale interfacial electrochemical reactions. To probe the mechanisms of solid electrolyte interphase (SEI) formation and to track Li nucleation and growth mechanisms from a standard organic battery electrolyte (LiPF6 in EC:DMC), we used in situ electrochemical scanning transmission electron microscopy (ec-S/TEM) to perform controlled electrochemical potential sweep measurements while simultaneously imaging site-specific structures resulting from electrochemical reactions. A combined quantitative electrochemical measurement and STEM imaging approach is used to demonstrate that chemically sensitive annular dark field STEM imaging can be used to estimate the density of the evolving SEI and to identify Li-containing phases formed in the liquid cell. We report that the SEI is approximately twice as dense as the electrolyte as determined from imaging and electron scattering theory. We also observe site-specific locations where Li nucleates and grows on the surface and edge of the glassy carbon electrode. Lastly, this report demonstrates the investigative power of quantitative nanoscale imaging combined with electrochemical measurements for studying fluid-solid interfaces and their evolving chemistries.}, number={3}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Sacci, Robert L. and Black, Jennifer M. and Balke, Nina and Dudney, Nancy J. and More, Karren L. and Unocic, Raymond R.}, year={2015}, month={Feb}, pages={2011–2018} }
 @article{balke_bassiri-gharb_lichtensteiger_2015, title={Preface to Special Topic: Piezoresponse Force Microscopy}, volume={118}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000360441900001&KeyUID=WOS:000360441900001}, DOI={10.1063/1.4927818}, abstractNote={First Page}, number={7}, journal={Journal of Applied Physics}, author={Balke, Nina and Bassiri-Gharb, Nazanin and Lichtensteiger, Celine}, year={2015} }
 @article{li_jesse_tselev_collins_yu_kravchenko_kalinin_balke_2015, title={Probing Local Bias-Induced Transitions Using Photothermal Excitation Contact Resonance Atomic Force Microscopy and Voltage Spectroscopy}, volume={9}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000349940500081&KeyUID=WOS:000349940500081}, DOI={10.1021/nn506753u}, abstractNote={Nanomechanical properties are closely related to the states of matter, including chemical composition, crystal structure, mesoscopic domain configuration, etc. Investigation of these properties at the nanoscale requires not only static imaging methods, e.g., contact resonance atomic force microscopy (CR-AFM), but also spectroscopic methods capable of revealing their dependence on various external stimuli. Here we demonstrate the voltage spectroscopy of CR-AFM, which was realized by combining photothermal excitation (as opposed to the conventional piezoacoustic excitation method) with the band excitation technique. We applied this spectroscopy to explore local bias-induced phenomena ranging from purely physical to surface electromechanical and electrochemical processes. Our measurements show that the changes in the surface properties associated with these bias-induced transitions can be accurately assessed in a fast and dynamic manner, using resonance frequency as a signature. With many of the advantages offered by photothermal excitation, contact resonance voltage spectroscopy not only is expected to find applications in a broader field of nanoscience but also will provide a basis for future development of other nanoscale elastic spectroscopies.}, number={2}, journal={Acs Nano}, author={Li, Qian and Jesse, Stephen and Tselev, Alexander and Collins, Liam and Yu, Pu and Kravchenko, Ivan and Kalinin, Sergei V. and Balke, Nina}, year={2015}, pages={1848–1857} }
 @article{tselev_klein_gassmann_jesse_li_kalinin_balke_2015, title={Quantitative Nanometer-Scale Mapping of Dielectric Tunability}, volume={2}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000363415300001&KeyUID=WOS:000363415300001}, DOI={10.1002/admi.201500088}, abstractNote={Two scanning probe microscopy techniques—near‐field scanning microwave microscopy (SMM) and piezoresponse force microscopy (PFM)—are used to characterize and image tunability in a thin (Ba,Sr)TiO3 film with nanometer scale spatial resolution. While sMIM allows direct probing of tunability by measurement of the change in the dielectric constant, in PFM, tunability can be extracted via electrostrictive response. The near‐field microwave imaging and PFM provide similar information about dielectric tunability with PFM capable to deliver quantitative information on tunability with a higher spatial resolution close to 15 nm. This is the first time, information about the dielectric tunability is available on such length scales.}, number={15}, journal={Advanced Materials Interfaces}, author={Tselev, Alexander and Klein, Andreas and Gassmann, Juergen and Jesse, Stephen and Li, Qian and Kalinin, Sergei V. and Balke, Nina}, year={2015} }
 @article{black_okatan_feng_cummings_kalinin_balke_2015, title={Topological defects in electric double layers of ionic liquids at carbon interfaces}, volume={15}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000364578900072&KeyUID=WOS:000364578900072}, DOI={10.1016/j.nanoen.2015.05.037}, abstractNote={The structure and properties of the electrical double layer in ionic liquids is of interest in a wide range of areas including energy storage, catalysis, lubrication, and many more. Theories describing the electrical double layer for ionic liquids have been proposed; however, a full molecular level description of the double layer is lacking. To date, studies have been predominantly focused on ion distributions normal to the surface; however, the 3D nature of the electrical double layer in ionic liquids requires a full picture of the double layer structure not only normal to the surface, but also in plane. Here we utilize 3D force mapping to probe the in plane structure of an ionic liquid at a graphite interface and report the direct observation of the structure and properties of topological defects. The observation of ion layering at structural defects such as step-edges, reinforced by molecular dynamics simulations, defines the spatial resolution of the method. Observation of defects allows for the establishment of the universality of ionic liquid behavior vs. separation from the carbon surface and to map internal defect structure. These studies offer a universal pathway for probing the internal structure of topological defects in soft condensed matter on the nanometer level in three dimensions.}, journal={Nano Energy}, author={Black, Jennifer M. and Okatan, M. Baris and Feng, Guang and Cummings, Peter T. and Kalinin, Sergei V. and Balke, Nina}, year={2015}, pages={737–745} }
 @article{yang_belianinov_strelcov_tebano_foglietti_di castro_schlueter_lee_baddorf_balke_et al._2014, title={Effect of Doping on Surface Reactivity and Conduction Mechanism in Samarium-Doped Ceria Thin Films}, volume={8}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000347138000062&KeyUID=WOS:000347138000062}, DOI={10.1021/nn505345c}, abstractNote={A systematic study by reversible and hysteretic electrochemical strain microscopy (ESM) in samples of cerium oxide with different Sm content and in several working conditions allows disclosing the microscopic mechanism underlying the difference in electrical conduction mechanism and related surface activity, such as water adsorption and dissociation with subsequent proton liberation. We have measured the behavior of the reversible hysteresis loops by changing temperature and humidity, both in standard ESM configuration and using the first-order reversal curve method. The measurements have been performed in much smaller temperature ranges with respect to alternative measuring techniques. Complementing our study with hard X-ray photoemission spectroscopy and irreversible scanning probe measurements, we find that water incorporation is favored until the doping with Sm is too high to allow the presence of Ce3+. The influence of doping on the surface reactivity clearly emerges from all of our experimental results. We find that at lower Sm concentration, proton conduction is prevalent, featured by lower activation energy and higher electrical conductivity. Defect concentrations determine the type of the prevalent charge carrier in a doping dependent manner.}, number={12}, journal={Acs Nano}, author={Yang, Nan and Belianinov, Alex and Strelcov, Evgheni and Tebano, Antonello and Foglietti, Vittorio and Di Castro, Daniele and Schlueter, Christoph and Lee, Tien-Lin and Baddorf, Arthur P. and Balke, Nina and et al.}, year={2014}, pages={12494–12501} }
 @article{eliseev_morozovska_ievlev_balke_maksymovych_tselev_kalinin_2014, title={Electrostrictive and electrostatic responses in contact mode voltage modulated scanning probe microscopies}, volume={104}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000337891200065&KeyUID=WOS:000337891200065}, DOI={10.1063/1.4882861}, abstractNote={Electromechanical response of solids underpins image formation mechanism of several scanning probe microscopy techniques including the piezoresponse force microscopy (PFM) and electrochemical strain microscopy (ESM). While the theory of linear piezoelectric and ionic responses are well developed, the contributions of quadratic effects including electrostriction and capacitive tip-surface forces to measured signal remain poorly understood. Here we analyze the electrostrictive and capacitive contributions to the PFM and ESM signals and discuss the implications of the dielectric tip-surface gap on these interactions.}, number={23}, journal={Applied Physics Letters}, author={Eliseev, Eugene A. and Morozovska, Anna N. and Ievlev, Anton V. and Balke, Nina and Maksymovych, Peter and Tselev, Alexander and Kalinin, Sergei V.}, year={2014} }
 @article{balke_maksymovych_jesse_kravchenko_li_kalinin_2014, title={Exploring Local Electrostatic Effects with Scanning Probe Microscopy: Implications for Piezoresponse Force Microscopy and Triboelectricity}, volume={8}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000343952600057&KeyUID=WOS:000343952600057}, DOI={10.1021/nn505176a}, abstractNote={The implementation of contact mode Kelvin probe force microscopy (cKPFM) utilizes the electrostatic interactions between tip and sample when the tip and sample are in contact with each other. Surprisingly, the electrostatic forces in contact are large enough to be measured even with tips as stiff as 4.5 N/m. As for traditional noncontact KPFM, the signal depends strongly on electrical properties of the sample, such as the dielectric constant, and the tip properties, such as the stiffness. Since the tip is in contact with the sample, bias-induced changes in the junction potential between tip and sample can be measured with higher lateral and temporal resolution compared to traditional noncontact KPFM. Significant and reproducible variations of tip-surface capacitance are observed and attributed to surface electrochemical phenomena. Observations of significant surface charge states at zero bias and strong hysteretic electromechanical responses at a nonferroelectric surface have significant implications for fields such as triboelectricity and piezoresponse force microscopy.}, number={10}, journal={Acs Nano}, author={Balke, Nina and Maksymovych, Petro and Jesse, Stephen and Kravchenko, Ivan I. and Li, Qian and Kalinin, Sergei V.}, year={2014}, pages={10229–10236} }
 @article{siemons_beekman_fowlkes_balke_tischler_xu_liu_gonzales_budai_christen_2014, title={Focused-ion-beam induced damage in thin films of complex oxide BiFeO3}, volume={2}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000332282800011&KeyUID=WOS:000332282800011}, DOI={10.1063/1.4866051}, abstractNote={An unexpected, strong deterioration of crystal quality is observed in epitaxial perovskite BiFeO3 films in which microscale features have been patterned by focused-ion-beam (FIB) milling. Specifically, synchrotron x-ray microdiffraction shows that the damaged region extends to tens of μm, but does not result in measureable changes to morphology or stoichiometry. Therefore, this change would go undetected with standard laboratory equipment, but can significantly influence local material properties and must be taken into account when using a FIB to manufacture nanostructures. The damage is significantly reduced when a thin metallic layer is present on top of the film during the milling process, clearly indicating that the reduced crystallinity is caused by ion beam induced charging.}, number={2}, journal={Apl Materials}, author={Siemons, W. and Beekman, C. and Fowlkes, J. D. and Balke, N. and Tischler, J. Z. and Xu, R. and Liu, W. and Gonzales, C. M. and Budai, J. D. and Christen, H. M.}, year={2014} }
 @article{collins_jesse_kilpatrick_tselev_varenyk_okatan_weber_kumar_balke_kalinin_et al._2014, title={Probing charge screening dynamics and electrochemical processes at the solid-liquid interface with electrochemical force microscopy}, volume={5}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000337503800015&KeyUID=WOS:000337503800015}, DOI={10.1038/ncomms4871}, abstractNote={The presence of mobile ions complicates the implementation of voltage-modulated scanning probe microscopy techniques such as Kelvin probe force microscopy (KPFM). Overcoming this technical hurdle, however, provides a unique opportunity to probe ion dynamics and electrochemical processes in liquid environments and the possibility to unravel the underlying mechanisms behind important processes at the solid–liquid interface, including adsorption, electron transfer and electrocatalysis. Here we describe the development and implementation of electrochemical force microscopy (EcFM) to probe local bias- and time-resolved ion dynamics and electrochemical processes at the solid–liquid interface. Using EcFM, we demonstrate contact potential difference measurements, consistent with the principles of open-loop KPFM operation. We also demonstrate that EcFM can be used to investigate charge screening mechanisms and electrochemical reactions in the probe–sample junction. We further establish EcFM as a force-based imaging mode, allowing visualization of the spatial variability of sample-dependent local electrochemical properties. Voltage-modulated scanning probe microscopy may elucidate important processes at solid–liquid interfaces, but it is complicated by the presence of mobile ions. By incorporating force sensitivity into a multidimensional measurement approach, Collins et al.present a technique that overcomes these limitations.}, journal={Nature Communications}, author={Collins, Liam and Jesse, Stephen and Kilpatrick, Jason I. and Tselev, Alexander and Varenyk, Oleksandr and Okatan, M. Baris and Weber, Stefan A. L. and Kumar, Amit and Balke, Nina and Kalinin, Sergei V. and et al.}, year={2014} }
 @article{agar_mangalam_damodaran_velarde_karthik_okatan_chen_jesse_balke_kalinin_et al._2014, title={Tuning Susceptibility via Misfit Strain in Relaxed Morphotropic Phase Boundary PbZr1-xTixO3 Epitaxial Thin Films}, volume={1}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000348283700019&KeyUID=WOS:000348283700019}, DOI={10.1002/admi.201400098}, abstractNote={Epitaxial strain is a powerful tool to manipulate the properties of ferroelectric materials. But despite extensive work in this regard, few studies have explored the effect of epitaxial strain on PbZr0.52Ti0.48O3. Here we explore how epitaxial strain impacts the structure and properties of 75 nm thick films of the morphotropic phase boundary composition. Single‐phase, fully epitaxial films are found to possess “relaxed” or nearly “relaxed” structures despite growth on a range of substrates. Subsequent studies of the dielectric and ferroelectric properties reveal films with low leakage currents facilitating the measurement of low‐loss hysteresis loops down to measurement frequencies of 30 mHz and dielectric response at background dc bias fields as large as 850 kV/cm. Despite a seeming insensitivity of the crystal structure to the epitaxial strain, the polarization and switching characteristics are found to vary with substrate. The elastic constraint from the substrate produces residual strains that dramatically alter the electric‐field response including quenching domain wall contributions to the dielectric permittivity and suppressing field‐induced structural reorientation. These results demonstrate that substrate mediated epitaxial strain of PbZr0.52Ti0.48O3 is more complex than in conventional ferroelectrics with discretely defined phases, yet can have a marked effect on the material and its responses.}, number={5}, journal={Advanced Materials Interfaces}, author={Agar, J. C. and Mangalam, R. V. K. and Damodaran, A. R. and Velarde, G. and Karthik, J. and Okatan, M. B. and Chen, Z. H. and Jesse, S. and Balke, N. and Kalinin, S. V. and et al.}, year={2014} }
 @article{black_walters_labuda_feng_hillesheim_dai_cummings_kalinin_proksch_balke_2013, title={Bias-Dependent Molecular-Level Structure of Electrical Double Layer in Ionic Liquid on Graphite}, volume={13}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000328439200031&KeyUID=WOS:000328439200031}, DOI={10.1021/nl4031083}, abstractNote={Here we report the bias-evolution of the electrical double layer structure of an ionic liquid on highly ordered pyrolytic graphite measured by atomic force microscopy. We observe reconfiguration under applied bias and the orientational transitions in the Stern layer. The synergy between molecular dynamics simulation and experiment provides a comprehensive picture of structural phenomena and long and short-range interactions, which improves our understanding of the mechanism of charge storage on a molecular level.}, number={12}, journal={Nano Letters}, author={Black, Jennifer M. and Walters, Deron and Labuda, Aleksander and Feng, Guang and Hillesheim, Patrick C. and Dai, Sheng and Cummings, Peter T. and Kalinin, Sergei V. and Proksch, Roger and Balke, Nina}, year={2013}, pages={5954–5960} }
 @article{vasudevan_wu_guest_baddorf_morozovska_eliseev_balke_nagarajan_maksymovych_kalinin_2013, title={Domain Wall Conduction and Polarization-Mediated Transport in Ferroelectrics}, volume={23}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000318999700010&KeyUID=WOS:000318999700010}, DOI={10.1002/adfm.201300085}, abstractNote={AbstractNanometer‐scale electronic transport in engineered interfaces in ferroelectrics, such as domains and topological defects, has emerged as a topic of broad interest due to potential applications in information storage, sensors and photovoltaic devices. Scanning probe microscopy (SPM) methods led to rapid growth in the field by enabling correlation of the unique functional properties with microstructural features in the aforementioned highly localized phenomena. In addition to conduction localized at interfaces, polarization‐mediated control of conduction through domains in nanoscale ferroelectrics suggests significant potential for use in memristor technologies. In parallel with experiment, theory based on thermodynamic Landau‐Ginzburg‐Devonshire (LGD) framework has seen rapid development, both rationalizing the observations, and hinting at possibilities for local, deterministic control of order parameters. These theories can successfully account for static interface conductivity at charged, nominally uncharged and topologically protected domain walls. Here, recent experimental and theoretical progress in SPM‐motivated studies on domain wall conduction in both standard and improper ferroelectrics are reviewed. SPM studies on transport through ferroelectrics reveal that both domains and topological defects in oxides can be exploited as individual elements for use in functional nanoscale devices. Future prospects of the field are discussed.}, number={20}, journal={Advanced Functional Materials}, author={Vasudevan, Rama K. and Wu, Weida and Guest, Jeffrey R. and Baddorf, Arthur P. and Morozovska, Anna N. and Eliseev, Eugene A. and Balke, Nina and Nagarajan, V. and Maksymovych, Peter and Kalinin, Sergei V.}, year={2013}, pages={2592–2616} }
 @article{arruda_lawton_kumar_unocic_kravchenko_zawodzinski_jesse_kalinin_balke_2013, title={In Situ Formation of Micron-Scale Li-Metal Anodes with High Cyclability}, volume={3}, ISSN={2162-8726 2162-8734}, url={http://dx.doi.org/10.1149/2.003401eel}, DOI={10.1149/2.003401eel}, abstractNote={Scanning probe microscopy methods have been used to electrodeposit and cycle micron-scale Li anodes deposited electrochemically under nanofabricated Au current collectors. An average Li volume of 5 × 108 nm3 was deposited and cycled with 100% coulombic efficiency for ∼160 cycles. Integrated charge/discharge values agree with before/after topography, as well as in situ dilatometry, suggesting this is a reliable method to study solid-state electrochemical processes. In this work we illustrate the possibility to deposit highly cyclable nanometer thick Li electrodes by mature SPM and nanofab techniques which can pave the way for inexpensive nanoscale battery arrays.}, number={1}, journal={ECS Electrochemistry Letters}, publisher={The Electrochemical Society}, author={Arruda, T. M. and Lawton, J. S. and Kumar, A. and Unocic, R. R. and Kravchenko, I. I. and Zawodzinski, T. A. and Jesse, S. and Kalinin, S. V. and Balke, N.}, year={2013}, month={Nov}, pages={A4–A7} }
 @article{kim_kelly_morozovska_rahani_strelcov_eliseev_jesse_biegalski_balke_benedek_et al._2013, title={Mechanical Control of Electroresistive Switching}, volume={13}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000330158900016&KeyUID=WOS:000330158900016}, DOI={10.1021/nl401411r}, abstractNote={Hysteretic metal-insulator transitions (MIT) mediated by ionic dynamics or ferroic phase transitions underpin emergent applications for nonvolatile memories and logic devices. The vast majority of applications and studies have explored the MIT coupled to the electric field or temperarture. Here, we argue that MIT coupled to ionic dynamics should be controlled by mechanical stimuli, the behavior we refer to as the piezochemical effect. We verify this effect experimentally and demonstrate that it allows both studying materials physics and enabling novel data storage technologies with mechanical writing and current-based readout.}, number={9}, journal={Nano Letters}, author={Kim, Yunseok and Kelly, Simon J. and Morozovska, Anna and Rahani, Ehsan Kabiri and Strelcov, Evgheni and Eliseev, Eugene and Jesse, Stephen and Biegalski, Michael D. and Balke, Nina and Benedek, Nicole and et al.}, year={2013}, pages={4068–4074} }
 @article{beekman_siemons_ward_chi_howe_biegalski_balke_maksymovych_farrar_romero_et al._2013, title={Phase Transitions, Phase Coexistence, and Piezoelectric Switching Behavior in Highly Strained BiFeO3 Films}, volume={25}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000332331300002&KeyUID=WOS:000332331300002}, DOI={10.1002/adma.201302066}, abstractNote={Highly strained BiFeO3 films transition into a true tetragonal state at 430 °C but remain polar to much higher temperatures (∼800 °C). Piezoelectric switching is only possible up to 300 °C, i.e., at temperatures for which strain stabilizes the stripe-like coexistence of multiple polymorphs.}, number={39}, journal={Advanced Materials}, author={Beekman, C. and Siemons, W. and Ward, T. Z. and Chi, M. and Howe, J. and Biegalski, M. D. and Balke, N. and Maksymovych, P. and Farrar, A. K. and Romero, J. B. and et al.}, year={2013}, pages={5561-+} }
 @article{wang_zhao_wang_gai_balke_chi_lee_tian_zhu_cheng_et al._2013, title={Room-Temperature Multiferroic Hexagonal LuFeO3 Films}, volume={110}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000320115000022&KeyUID=WOS:000320115000022}, DOI={10.1103/PhysRevLett.110.237601}, abstractNote={The crystal and magnetic structures of single-crystalline hexagonal LuFeO(3) films have been studied using x-ray, electron, and neutron diffraction methods. The polar structure of these films are found to persist up to 1050 K; and the switchability of the polar behavior is observed at room temperature, indicating ferroelectricity. An antiferromagnetic order was shown to occur below 440 K, followed by a spin reorientation resulting in a weak ferromagnetic order below 130 K. This observation of coexisting multiple ferroic orders demonstrates that hexagonal LuFeO(3) films are room-temperature multiferroics.}, number={23}, journal={Physical Review Letters}, author={Wang, Wenbin and Zhao, Jun and Wang, Wenbo and Gai, Zheng and Balke, Nina and Chi, Miaofang and Lee, Ho Nyung and Tian, Wei and Zhu, Leyi and Cheng, Xuemei and et al.}, year={2013} }
 @article{black_feng_fulvio_hillesheim_dai_gogotsi_cummings_kalinin_balke_2014, title={Strain-Based In Situ Study of Anion and Cation Insertion into Porous Carbon Electrodes with Different Pore Sizes}, volume={4}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000331709900005&KeyUID=WOS:000331709900005}, DOI={10.1002/aenm.201300683}, abstractNote={The expansion of porous carbon electrodes in a room temperature ionic liquid (RTIL) is studied using in situ atomic force microscopy (AFM). The effect of carbon surface area and pore size/pore size distribution on the observed strain profile and ion kinetics is examined. Additionally, the influence of the potential scan rate on the strain response is investigated. By analyzing the strain data at various potential scan rates, information on ion kinetics in the different carbon materials is obtained. Molecular dynamics (MD) simulations are performed to compare with and provide molecular insights into the experimental results; this is the first MD work investigating the pressure exerted on porous electrodes under applied potential in a RTIL electrolyte. Using MD, the pressure exerted on the pore wall is calculated as a function of potential/charge for both a micropore (1.2 nm) and a mesopore (7.0 nm). The shape of the calculated pressure profile matches closely with the strain profiles observed experimentally.}, number={3}, journal={Advanced Energy Materials}, author={Black, Jennifer M. and Feng, Guang and Fulvio, Pasquale F. and Hillesheim, Patrick C. and Dai, Sheng and Gogotsi, Yury and Cummings, Peter T. and Kalinin, Sergei V. and Balke, Nina}, year={2014} }
 @article{arruda_kumar_jesse_veith_tselev_baddorf_balke_kalinin_2013, title={Toward Quantitative Electrochemical Measurements on the Nanoscale by Scanning Probe Microscopy: Environmental and Current Spreading Effects}, volume={7}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000330016900079&KeyUID=WOS:000330016900079}, DOI={10.1021/nn4034772}, abstractNote={The application of electric bias across tip-surface junctions in scanning probe microscopy can readily induce surface and bulk electrochemical processes that can be further detected though changes in surface topography, Faradaic or conductive currents, or electromechanical strain responses. However, the basic factors controlling tip-induced electrochemical processes, including the relationship between applied tip bias and the thermodynamics of local processes, remains largely unexplored. Using the model Li-ion reduction reaction on the surface in Li-ion conducting glass ceramic, we explore the factors controlling Li-metal formation and find surprisingly strong effects of atmosphere and back electrode composition on the process. We find that reaction processes are highly dependent on the nature of the counter electrode and environmental conditions. Using a nondepleting Li counter electrode, Li particles could grow significantly larger and faster than a depleting counter electrode. Significant Li ion depletion leads to the inability for further Li reduction. Time studies suggest that Li diffusion replenishes the vacant sites after ∼12 h. These studies suggest the feasibility of SPM-based quantitative electrochemical studies under proper environmental controls, extending the concepts of ultramicroelectrodes to the single-digit nanometer scale.}, number={9}, journal={Acs Nano}, author={Arruda, Thomas M. and Kumar, Amit and Jesse, Stephen and Veith, Gabriel M. and Tselev, Alexander and Baddorf, Arthur P. and Balke, Nina and Kalinin, Sergei V.}, year={2013}, pages={8175–8182} }
 @article{huijben_yu_martin_molegraaf_chu_holcomb_balke_rijnders_ramesh_2013, title={Ultrathin Limit of Exchange Bias Coupling at Oxide Multiferroic/Ferromagnetic Interfaces}, volume={25}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000327692100014&KeyUID=WOS:000327692100014}, DOI={10.1002/adma.201300940}, abstractNote={Exchange bias coupling at the multiferroic- ferromagnetic interface in BiFeO₃ /La₀.₇ Sr₀.₃ MnO₃ heterostructures exhibits a critical thickness for ultrathin BiFeO₃ layers of 5 unit cells (2 nm). Linear dichroism measurements demonstrate the dependence on the BiFeO₃ layer thickness with a strong reduction for ultrathin layers, indicating diminished antiferromagnetic ordering that prevents interfacial exchange bias coupling.}, number={34}, journal={Advanced Materials}, author={Huijben, M. and Yu, P. and Martin, L. W. and Molegraaf, H. J. A. and Chu, Y. H. and Holcomb, M. B. and Balke, N. and Rijnders, G. and Ramesh, R.}, year={2013}, pages={4739–4745} }
 @article{beekman_siemons_ward_budai_tischler_xu_liu_balke_nam_christen_2013, title={Unit cell orientation of tetragonal-like BiFeO3 thin films grown on highly miscut LaAlO3 substrates}, volume={102}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000320621600033&KeyUID=WOS:000320621600033}, DOI={10.1063/1.4809601}, abstractNote={Synchrotron and lab-scale x-ray diffraction shows that tetragonal-like T′-BiFeO3 films on miscut LaAlO3 substrates (α < 5°) exhibit (00l)-planes tilted away from those of the substrate as predicted by the “Nagai model” (except for miscut < 0.2°). Tilts as large as 1° are achieved even in 100 nm thick films, strikingly larger than those observed in other perovskites. We attribute this to the large c/a ratio and the high crystalline coherency of the T′-BiFeO3/LaAlO3 interface. This coherency is possible through an observed “diagonal-on-diagonal” film/substrate alignment. Interestingly, the substrate miscut does not influence the relative population of monoclinic domains.}, number={22}, journal={Applied Physics Letters}, author={Beekman, C. and Siemons, W. and Ward, T. Z. and Budai, J. D. and Tischler, J. Z. and Xu, R. and Liu, W. and Balke, N. and Nam, J. H. and Christen, H. M.}, year={2013} }
 @article{balke_winchester_ren_chu_morozovska_eliseev_huijben_vasudevan_maksymovych_britson_et al._2012, title={Enhanced electric conductivity at ferroelectric vortex cores in BiFeO3}, volume={8}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298423000021&KeyUID=WOS:000298423000021}, number={1}, journal={Nature Physics}, author={Balke, Nina and Winchester, Benjamin and Ren, Wei and Chu, Ying Hao and Morozovska, Anna N. and Eliseev, Eugene A. and Huijben, Mark and Vasudevan, Rama K. and Maksymovych, Petro and Britson, Jason and et al.}, year={2012}, pages={81–88} }
 @article{balke_jesse_chu_kalinin_2012, title={High-Frequency Electromechanical Imaging of Ferroelectrics in a Liquid Environment}, volume={6}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000305661300111&KeyUID=WOS:000305661300111}, DOI={10.1021/nn301489g}, abstractNote={The coupling between electrical and mechanical phenomena is a ubiquitous feature of many information and energy storage materials and devices. In addition to involvement in performance and degradation mechanisms, electromechanical effects underpin a broad spectrum of nanoscale imaging and spectroscopies including piezoresponse force and electrochemical strain microscopies. Traditionally, these studies are conducted under ambient conditions. However, applications related to imaging energy storage and electrophysiological phenomena require operation in a liquid phase and therefore the development of electromechanical probing techniques suitable to liquid environments. Due to the relative high conductivity of most liquids and liquid decomposition at low voltages, the transfer of characterization techniques from ambient to liquid is not straightforward. Here we present a detailed study of ferroelectric domain imaging and manipulation in thin film BiFeO(3) using piezoresponse force microscopy in liquid environments as model systems for electromechanical phenomena in general. We explore the use of contact resonance enhancement and the application of multifrequency excitation and detection principles to overcome the experimental problems introduced by a liquid environment. Understanding electromechanical sample characterization in liquid is a key aspect not only for ferroelectric oxides but also for biological and electrochemical sample systems.}, number={6}, journal={Acs Nano}, author={Balke, Nina and Jesse, Stephen and Chu, Ying-Hao and Kalinin, Sergei V.}, year={2012}, pages={5559–5565} }
 @article{arruda_heon_presser_hillesheim_dai_gogotsi_kalinin_balke_2013, title={In situ tracking of the nanoscale expansion of porous carbon electrodes}, volume={6}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000312337700027&KeyUID=WOS:000312337700027}, DOI={10.1039/c2ee23707e}, abstractNote={Electrochemical double layer capacitors (EDLC) are rapidly emerging as a promising energy storage technology offering extremely large power densities. Despite significant experimental progress, nanoscale operation mechanisms of the EDLCs remain poorly understood and it is difficult to separate processes at multiple time and length scales involved in operation including that of double layer charging and ionic mass transport. Here we explore the functionality of EDLC microporous carbon electrodes using a combination of classical electrochemical measurements and scanning probe microscopy based dilatometry, thus separating individual stages in charge/discharge processes based on strain generation. These methods allowed us to observe two distinct modes of EDLC charging, one fast charging of the double layer unassociated with strain, and another much slower mass transport related charging exhibiting significant sample volume changes. These studies open the pathway for the exploration of electrochemical systems with multiple processes involved in the charge and discharge, and investigation of the kinetics of those processes.}, number={1}, journal={Energy & Environmental Science}, author={Arruda, Thomas M. and Heon, Min and Presser, Volker and Hillesheim, Patrick C. and Dai, Sheng and Gogotsi, Yury and Kalinin, Sergei V. and Balke, Nina}, year={2013}, pages={225–231} }
 @article{balke_kalnaus_dudney_daniel_jesse_kalinin_2012, title={Local Detection of Activation Energy for Ionic Transport in Lithium Cobalt Oxide}, volume={12}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000306296200008&KeyUID=WOS:000306296200008}, DOI={10.1021/nl300219g}, abstractNote={Local activation energy for ionic diffusion is probed on the nanometer level in LiCoO(2) thin films using variable temperature electrochemical strain microscopy (ESM). The high spatial resolution of ESM allows one to extract information about ionic activation energies on the level of individual grains and grain facets, thus bridging the lengths scales of atomistic calculations and traditional macroscopic experiments. A series of control experiments have been performed and possible signal generating mechanisms are discussed to explain the temperature-dependent ESM measurements.}, number={7}, journal={Nano Letters}, author={Balke, Nina and Kalnaus, Sergiy and Dudney, Nancy J. and Daniel, Claus and Jesse, Stephen and Kalinin, Sergei V.}, year={2012}, pages={3399–3403} }
 @article{heredia_meunier_bdikin_gracio_balke_jesse_tselev_agarwal_sumpter_kalinin_et al._2012, title={Nanoscale Ferroelectricity in Crystalline gamma-Glycine}, volume={22}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000306315200011&KeyUID=WOS:000306315200011}, DOI={10.1002/adfm.201103011}, abstractNote={AbstractFerroelectrics are multifunctional materials that reversibly change their polarization under an electric field. Recently, the search for new ferroelectrics has focused on organic and bio‐organic materials, where polarization switching is used to record/retrieve information in the form of ferroelectric domains. This progress has opened a new avenue for data storage, molecular recognition, and new self‐assembly routes. Crystalline glycine is the simplest amino acid and is widely used by living organisms to build proteins. Here, it is reported for the first time that γ‐glycine, which has been known to be piezoelectric since 1954, is also a ferroelectric, as evidenced by local electromechanical measurements and by the existence of as‐grown and switchable ferroelectric domains in microcrystals grown from the solution. The experimental results are rationalized by molecular simulations that establish that the polarization vector in γ‐glycine can be switched on the nanoscale level, opening a pathway to novel classes of bioelectronic logic and memory devices.}, number={14}, journal={Advanced Functional Materials}, author={Heredia, Alejandro and Meunier, Vincent and Bdikin, Igor K. and Gracio, Jose and Balke, Nina and Jesse, Stephen and Tselev, Alexander and Agarwal, Pratul K. and Sumpter, Bobby G. and Kalinin, Sergei V. and et al.}, year={2012}, pages={2996–3003} }
 @article{dittmer_jo_roedel_kalinin_balke_2012, title={Nanoscale Insight Into Lead-Free BNT-BT-xKNN}, volume={22}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000309886700004&KeyUID=WOS:000309886700004}, DOI={10.1002/adfm.201200592}, abstractNote={AbstractPiezoresponse force microscopy (PFM) is used to afford insight into the nanoscale electromechanical behavior of lead‐free piezoceramics. Materials based on Bi1/2Na1/2TiO3 exhibit high strains mediated by a field‐induced phase transition. Using the band excitation technique the initial domain morphology, the poling behavior, the switching behavior, and the time‐dependent phase stability in the pseudo‐ternary system (1–x)(0.94Bi1/2Na1/2TiO3‐0.06BaTiO3)‐xK0.5Na0.5NbO3 (0 <= x <= 18 mol%) are revealed. In the base material (x = 0 mol%), macroscopic domains and ferroelectric switching can be induced from the initial relaxor state with sufficiently high electric field, yielding large macroscopic remanent strain and polarization. The addition of KNN increases the threshold field required to induce long range order and decreases the stability thereof. For x = 3 mol% the field‐induced domains relax completely, which is also reflected in zero macroscopic remanence. Eventually, no long range order can be induced for x >= 3 mol%. This PFM study provides a novel perspective on the interplay between macroscopic and nanoscopic material properties in bulk lead‐free piezoceramics.}, number={20}, journal={Advanced Functional Materials}, author={Dittmer, Robert and Jo, Wook and Roedel, Juergen and Kalinin, Sergei and Balke, Nina}, year={2012}, pages={4208–4215} }
 @article{balke_tselev_arruda_jesse_chu_kalinin_2012, title={Probing Local Electromechanical Effects in Highly Conductive Electrolytes}, volume={6}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000311521700087&KeyUID=WOS:000311521700087}, DOI={10.1021/nn3038868}, abstractNote={The functionality of a variety of materials and devices is strongly coupled with electromechanical effects which can be used to characterize their functionality. Of high interest is the investigation of these electromechanical effects on the nanoscale which can be achieved by using scanning probe microscopy. Here, an electrical bias is applied locally to the scanning probe tip, and the mechanical sample response is detected. In some applications with electromechanical phenomena, such as energy storage or for biological samples, a liquid environment is required to provide full functionality and sample stability. However, electromechanical sample characterization has mostly been applied in air or under vacuum due to the difficulties of applying local electric fields in a conductive environment. Here, we present a detailed study of piezoresponse force microscopy of ferroelectric samples in liquid environments as a model system for electromechanical effects in general. The ionic strength of the liquid is varied, and possibilities and limitations of the technique are explored. Numerical simulations are used to explain the observed phenomena and used to suggest strategies to work in liquid environments with high ionic strength.}, number={11}, journal={Acs Nano}, author={Balke, Nina and Tselev, Alexander and Arruda, Thomas M. and Jesse, Stephen and Chu, Ying-Hao and Kalinin, Sergei V.}, year={2012}, pages={10139–10146} }
 @article{balke_bonnell_ginger_kemerink_2012, title={Scanning probes for new energy materials: Probing local structure and function}, volume={37}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000306367300010&KeyUID=WOS:000306367300010}, DOI={10.1557/mrs.2012.141}, abstractNote={Abstract}, number={7}, journal={Mrs Bulletin}, author={Balke, Nina and Bonnell, Dawn and Ginger, David S. and Kemerink, Martijn}, year={2012}, pages={633–637} }
 @article{balke_eliseev_jesse_kalnaus_daniel_dudney_morozovska_kalinin_2012, title={Three-dimensional vector electrochemical strain microscopy}, volume={112}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000309072200021&KeyUID=WOS:000309072200021}, DOI={10.1063/1.4746085}, abstractNote={Three-dimensional vector imaging of bias-induced displacements of surfaces of ionically conductive materials using electrochemical strain microscopy (ESM) is demonstrated for model polycrystalline LiCoO2 surface. We demonstrate that resonance enhanced imaging using band excitation detection can be performed both for out-of-plane and in-plane response components at flexural and torsional resonances of the cantilever, respectively. The image formation mechanism in vector ESM is analyzed and relationship between measured signal and grain orientation is discussed.}, number={5}, journal={Journal of Applied Physics}, author={Balke, N. and Eliseev, E. A. and Jesse, S. and Kalnaus, S. and Daniel, C. and Dudney, N. J. and Morozovska, A. N. and Kalinin, S. V.}, year={2012} }
 @article{maksymovych_huijben_pan_jesse_balke_chu_chang_borisevich_baddorf_rijnders_et al._2012, title={Ultrathin limit and dead-layer effects in local polarization switching of BiFeO3}, volume={85}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000299868400001&KeyUID=WOS:000299868400001}, DOI={10.1103/PhysRevB.85.014119}, abstractNote={Using piezoresponse force microscopy in an ultrahigh vacuum, polarization switching has been detected and quantified in epitaxial BiFeO3 films from 200 to about 4 unit cells thick. Local remnant piezoresponse was utilized to probe both ferroelectric properties and effects of imperfect electrical contacts. It was found that the shape of electromechanical hysteresis loops is strongly influenced by an extrinsic dielectric gap, primarily through the suppressing effect of the depolarizing field on the spontaneous polarization in the ultrathin films. Furthermore, statistical analysis of the hysteresis loops has revealed lateral variation of the extrinsic dielectric gap with sub–10-nm resolution. Robust and reproducible ferroelectric properties of nanoscale BiFeO3 indicate its potential for nanoscale applications in information storage and spintronics.}, number={1}, journal={Physical Review B}, author={Maksymovych, Peter and Huijben, Mark and Pan, Minghu and Jesse, Stephen and Balke, Nina and Chu, Ying-Hao and Chang, Hye Jung and Borisevich, Albina Y. and Baddorf, Arthur P. and Rijnders, Guus and et al.}, year={2012} }
 @article{guo_jesse_kalnaus_balke_daniel_kalinin_2011, title={Direct Mapping of Ion Diffusion Times on LiCoO2 Surfaces with Nanometer Resolution}, volume={158}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000292154300018&KeyUID=WOS:000292154300018}, DOI={10.1149/1.3604759}, abstractNote={The strong coupling between the molar volume and mobile ion concentration in ionically-conductive solids is used for spatially-resolved studies of ionic transport on the polycrystalline LiCoO2 surface by time-resolved spectroscopy. Strong variability between ionic transport at the grain boundaries and within the grains is observed, and the relationship between relaxation and hysteresis loop formation is established. The use of the strain measurements allows ionic transport be probed on the nanoscale, and suggests enormous potential for probing ionic materials and devices.}, number={8}, journal={Journal of the Electrochemical Society}, author={Guo, S. and Jesse, S. and Kalnaus, S. and Balke, N. and Daniel, C. and Kalinin, S. V.}, year={2011}, pages={A982–A990} }
 @article{jesse_balke_eliseev_tselev_dudney_morozovska_kalinin_2011, title={Direct Mapping of Ionic Transport in a Si Anode on the Nanoscale: Time Domain Electrochemical Strain Spectroscopy Study}, volume={5}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298316700040&KeyUID=WOS:000298316700040}, DOI={10.1021/nn203141g}, abstractNote={Local Li-ion transport in amorphous silicon is studied on the nanometer scale using time domain electrochemical strain microscopy (ESM). A strong variability of ionic transport controlled by the anode surface morphology is observed. The observed relaxing and nonrelaxing response components are discussed in terms of local and global ionic transport mechanisms, thus establishing the signal formation mechanisms in ESM. This behavior is further correlated with local conductivity measurements. The implications of these studies for Si-anode batteries are discussed. The universal presence of concentration-strain coupling suggests that ESM and associated time and voltage spectroscopies can be applied to a broad range of electrochemical systems ranging from batteries to fuel cells.}, number={12}, journal={Acs Nano}, author={Jesse, Stephen and Balke, Nina and Eliseev, Eugene and Tselev, Alexander and Dudney, Nancy J. and Morozovska, Anna N. and Kalinin, Sergei V.}, year={2011}, pages={9682–9695} }
 @article{kalinin_kumar_balke_mccorkle_guo_arruda_jesse_2011, title={ESM of Ionic and Electrochemical Phenomena on the Nanoscale}, volume={169}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000302757100003&KeyUID=WOS:000302757100003}, number={11}, journal={Advanced Materials & Processes}, author={Kalinin, Sergei and Kumar, Amit and Balke, Nina and McCorkle, Morgan and Guo, Senli and Arruda, Thomas and Jesse, Stephen}, year={2011}, pages={30–34} }
 @article{vasudevan_chen_tai_balke_wu_bhattacharya_chen_chu_lin_kalinin_et al._2011, title={Exploring Topological Defects in Epitaxial BiFeO3 Thin Films}, volume={5}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000287553800022&KeyUID=WOS:000287553800022}, DOI={10.1021/nn102099z}, abstractNote={Using a combination of piezoresponse force microscopy (PFM) and phase-field modeling, we demonstrate ubiquitous formation of center-type and possible ferroelectric closure domain arrangements during polarization switching near the ferroelastic domain walls in (100) oriented rhombohedral BiFeO(3). The formation of these topological defects is determined from the vertical and lateral PFM data and confirmed from the reversible changes in surface topography. These observations provide insight into the mechanisms of tip-induced ferroelastic domain control and suggest that formation of topological defect states under the action of local defect- and tip-induced fields is much more common than previously believed.}, number={2}, journal={Acs Nano}, author={Vasudevan, Rama K. and Chen, Yi-Chun and Tai, Hsiang-Hua and Balke, Nina and Wu, Pingping and Bhattacharya, Saswata and Chen, L. Q. and Chu, Ying-Hao and Lin, I. Nan and Kalinin, Sergei V. and et al.}, year={2011}, pages={879–887} }
 @article{kalinin_balke_jesse_tselev_kumar_arruda_guo_proksch_2011, title={Li-ion dynamics and reactivity on the nanoscale}, volume={14}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000297256200018&KeyUID=WOS:000297256200018}, number={11}, journal={Materials Today}, author={Kalinin, Sergei and Balke, Nina and Jesse, Stephen and Tselev, Alexander and Kumar, Amit and Arruda, Thomas M. and Guo, Senli and Proksch, Roger}, year={2011}, pages={548–558} }
 @article{jo_chen_sichel_baek_smith_balke_kalinin_holt_maser_evans-lutterodt_et al._2011, title={Structural Consequences of Ferroelectric Nanolithography}, volume={11}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000293665600005&KeyUID=WOS:000293665600005}, DOI={10.1021/nl2009873}, abstractNote={Domains of remnant polarization can be written into ferroelectrics with nanoscale precision using scanning probe nanolithography techniques such as piezoresponse force microscopy (PFM). Understanding the structural effects accompanying this process has been challenging due to the lack of appropriate structural characterization tools. Synchrotron X-ray nanodiffraction provides images of the domain structure written by PFM into an epitaxial Pb(Zr,Ti)O(3) thin film and simultaneously reveals structural effects arising from the writing process. A coherent scattering simulation including the superposition of the beams simultaneously diffracted by multiple mosaic blocks provides an excellent fit to the observed diffraction patterns. Domains in which the polarization is reversed from the as-grown state have a strain of up to 0.1% representing the piezoelectric response to unscreened surface charges. An additional X-ray microdiffraction study of the photon-energy dependence of the difference in diffracted intensity between opposite polarization states shows that this contrast has a crystallographic origin. The sign and magnitude of the intensity contrast between domains of opposite polarization are consistent with the polarization expected from PFM images and with the writing of domains through the entire thickness of the ferroelectric layer. The strain induced by writing provides a significant additional contribution to the increased free energy of the written domain state with respect to a uniformly polarized state.}, number={8}, journal={Nano Letters}, author={Jo, Ji Young and Chen, Pice and Sichel, Rebecca J. and Baek, Seung-Hyub and Smith, Ryan T. and Balke, Nina and Kalinin, Sergei V. and Holt, Martin V. and Maser, Joerg and Evans-Lutterodt, Kenneth and et al.}, year={2011}, pages={3080–3084} }
 @article{kalinin_jesse_tselev_baddorf_balke_2011, title={The Role of Electrochemical Phenomena in Scanning Probe Microscopy of Ferroelectric Thin Films}, volume={5}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000293035200046&KeyUID=WOS:000293035200046}, DOI={10.1021/nn2013518}, abstractNote={Applications of piezoresponse force microscopy and conductive atomic force microscopy to ferroelectric thin films necessitate understanding of the possible bias-induced electrochemical reactivity of oxide surfaces. These range from reversible ionic surface charging (possibly coupled to polarization) and vacancy and proton injection to partially reversible vacancy ordering, to irreversible electrochemical degradation of the film and bottom electrode. Here, the electrochemical phenomena induced by a biased tip are analyzed and both theoretical and experimental criteria for their identification are summarized.}, number={7}, journal={Acs Nano}, author={Kalinin, Sergei V. and Jesse, Stephen and Tselev, Alexander and Baddorf, Arthur P. and Balke, Nina}, year={2011}, pages={5683–5691} }
 @article{chung_balke_kalinin_garcia_2011, title={Virtual Electrochemical Strain Microscopy of Polycrystalline LiCoO2 Films}, volume={158}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000294063000004&KeyUID=WOS:000294063000004}, DOI={10.1149/1.3619775}, abstractNote={A recently developed technique, electrochemical strain microscopy (ESM), utilizes the strong coupling between ionic current and anisotropic volumetric chemical expansion of lithium-ion electrode materials to dynamically probe the sub-one-hundred? nm inter-facial kinetic intercalation properties. A numerical technique based on the finite element method was developed to analyze the underlying physics that govern the ESM signal generation and establish relations to battery performance. The performed analysis demonstrates that the diffusion path within a thin film is tortuous and the extent of lithium diffusion into the electrode is dependent on the SPM-tip-imposed overpotential frequency. The detected surface actuation gives rise to the development of an electromechanical hysteresis loop whose shape is dependent on grain size and overpotential frequency. Shape and tilting angle of the loop are classified into low and high frequency regimes, separated by a transition frequency which is also a function of lithium diffusivity and grain size, f{sub T} = D//{sup 2}. Research shows that the crystallographic orientation of the surface actuated grain has a significant impact on the shape of the loop. The polycrystalline crystallographic orientation of the grains induces a diffusion path network in the electrode which impacts on the mechanical reliability of the battery. Simulations demonstrate thatmore » continuous battery cycling results in a cumulative capacity loss as a result of the hysteric non-reversible lithium intercalation. Furthermore, results suggest that ESM has the capability to infer the local out-of-plane lithium diffusivity and the out-of-plane contribution to Vegard tensor.« less}, number={10}, journal={Journal of the Electrochemical Society}, author={Chung, Ding-Wen and Balke, Nina and Kalinin, Sergei V. and Garcia, R. Edwin}, year={2011}, pages={A1083–A1089} }
 @article{chang_kalinin_yang_yu_bhattacharya_wu_balke_jesse_chen_ramesh_et al._2011, title={Watching domains grow: In-situ studies of polarization switching by combined scanning probe and scanning transmission electron microscopy}, volume={110}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000294968600015&KeyUID=WOS:000294968600015}, DOI={10.1063/1.3623779}, abstractNote={Ferroelectric domain nucleation and growth in multiferroic BiFeO3 films is observed directly by applying a local electric field with a conductive tip inside a scanning transmission electron microscope. The nucleation and growth of a ferroelastic domain and its interaction with pre-existing 71° domain walls are observed and compared with the results of phase-field modeling. In particular, a preferential nucleation site and direction-dependent pinning of domain walls are observed due to slow kinetics of metastable switching in the sample without a bottom electrode. These in situ spatially resolved observations of a first-order bias-induced phase transition reveal the mesoscopic mechanisms underpinning functionality of a wide range of multiferroic materials.}, number={5}, journal={Journal of Applied Physics}, author={Chang, Hyejung and Kalinin, Sergei V. and Yang, Seungyeul and Yu, Pu and Bhattacharya, Saswata and Wu, Ping P. and Balke, Nina and Jesse, Stephen and Chen, Long Q. and Ramesh, Ramamoorthy and et al.}, year={2011} }
 @article{balke_jesse_kim_adamczyk_ivanov_dudney_kalinin_2010, title={Decoupling Electrochemical Reaction and Diffusion Processes in Ionically-Conductive Solids on the Nanometer Scale}, volume={4}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000285449100037&KeyUID=WOS:000285449100037}, DOI={10.1021/nn101502x}, abstractNote={We have developed a scanning probe microscopy approach to explore voltage-controlled ion dynamics in ionically conductive solids and decouple transport and local electrochemical reactivity on the nanometer scale. Electrochemical strain microscopy allows detection of bias-induced ionic motion through the dynamic (0.1-1 MHz) local strain. Spectroscopic modes based on low-frequency (∼1 Hz) voltage sweeps allow local ion dynamics to be probed locally. The bias dependence of the hysteretic strain response accessed through first-order reversal curve (FORC) measurements demonstrates that the process is activated at a certain critical voltage and is linear above this voltage everywhere on the surface. This suggests that FORC spectroscopic ESM data separates local electrochemical reaction and transport processes. The relevant parameters such as critical voltage and effective mobility can be extracted for each location and correlated with the microstructure. The evolution of these behaviors with the charging of the amorphous Si anode in a thin-film Li-ion battery is explored. A broad applicability of this method to other ionically conductive systems is predicted.}, number={12}, journal={Acs Nano}, author={Balke, Nina and Jesse, Stephen and Kim, Yoongu and Adamczyk, Leslie and Ivanov, Ilia N. and Dudney, Nancy J. and Kalinin, Sergei V.}, year={2010}, pages={7349–7357} }
 @article{balke_gajek_tagantsev_martin_chu_ramesh_kalinin_2010, title={Direct Observation of Capacitor Switching Using Planar Electrodes}, volume={20}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000284000200006&KeyUID=WOS:000284000200006}, DOI={10.1002/adfm.201000475}, abstractNote={AbstractFerroelectric polarization switching in epitaxial (110) BiFeO3 films is studied using piezoresponse force microscopy of a model in‐plane capacitor structure. The electrode orientation is chosen such that only two active domain variants exist. Studies of the kinetics of domain evolution allows clear visualization of nucleation sites, as well as forward and lateral growth stages of domain formation. It is found that the location of the reverse‐domain nucleation is correlated with the direction of switching in a way that the polarization in the domains nucleated at an electrode is always directed away from it. The role of interface charge injection and surface screening charge on switching mechanisms is explored, and the nucleation is shown to be controllable by the bias history of the sample. Finally, the manipulation of domain nucleation through domain structure engineering is illustrated. These studies pave the way for the engineering and design of the ferroelectric device structures through control of individual steps of the switching process.}, number={20}, journal={Advanced Functional Materials}, author={Balke, Nina and Gajek, Martin and Tagantsev, Alexander K. and Martin, Lane W. and Chu, Ying-Hao and Ramesh, Ramamoorthy and Kalinin, Sergei V.}, year={2010}, pages={3466–3475} }
 @article{jang_kumar_denev_biegalski_maksymovych_bark_nelson_folkman_baek_balke_et al._2010, title={Ferroelectricity in Strain-Free SrTiO3 Thin Films}, volume={104}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000277699600052&KeyUID=WOS:000277699600052}, DOI={10.1103/PhysRevLett.104.197601}, abstractNote={Biaxial strain is known to induce ferroelectricity in thin films of nominally nonferroelectric materials such as SrTiO3. By a direct comparison of the strained and strain-free SrTiO3 films using dielectric, ferroelectric, Raman, nonlinear optical and nanoscale piezoelectric property measurements, we conclude that all SrTiO3 films and bulk crystals are relaxor ferroelectrics, and the role of strain is to stabilize longer-range correlation of preexisting nanopolar regions, likely originating from minute amounts of unintentional Sr deficiency in nominally stoichiometric samples. These findings highlight the sensitive role of stoichiometry when exploring strain and epitaxy-induced electronic phenomena in oxide films, heterostructures, and interfaces.}, number={19}, journal={Physical Review Letters}, author={Jang, H. W. and Kumar, A. and Denev, S. and Biegalski, M. D. and Maksymovych, P. and Bark, C. W. and Nelson, C. T. and Folkman, C. M. and Baek, S. H. and Balke, N. and et al.}, year={2010} }
 @article{kalinin_balke_2010, title={Local Electrochemical Functionality in Energy Storage Materials and Devices by Scanning Probe Microscopies: Status and Perspectives}, volume={22}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000282910100009&KeyUID=WOS:000282910100009}, DOI={10.1002/adma.201001190}, abstractNote={AbstractEnergy storage and conversion systems are an integral component of emerging green technologies, including mobile electronic devices, automotive, and storage components of solar and wind energy economics. Despite the rapidly expanding manufacturing capabilities and wealth of phenomenological information on the macroscopic device behaviors, the microscopic mechanisms underpinning battery and fuel cell operations in the nanometer–micrometer range are virtually unknown. This lack of information is due to the dearth of experimental techniques capable of addressing elementary mechanisms involved in battery operation, including electronic and ion transport, vacancy injection, and interfacial reactions, on the nanometer scale. In this article, a brief overview of scanning probe microscopy (SPM) methods addressing nanoscale electrochemical functionalities is provided and compared with macroscopic electrochemical methods. Future applications of emergent SPM methods, including near field optical, electromechanical, microwave, and thermal probes and combined SPM‐(S)TEM (scanning transmission electron microscopy) methods in energy storage and conversion materials are discussed.}, number={35}, journal={Advanced Materials}, author={Kalinin, Sergei V. and Balke, Nino}, year={2010}, pages={E193–E209} }
 @article{morozovska_eliseev_balke_kalinin_2010, title={Local probing of ionic diffusion by electrochemical strain microscopy: Spatial resolution and signal formation mechanisms}, volume={108}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000282478900045&KeyUID=WOS:000282478900045}, DOI={10.1063/1.3460637}, abstractNote={Electrochemical insertion-deintercalation reactions are typically associated with significant change in molar volume of the host compound. This strong coupling between ionic currents and strains underpins image formation mechanisms in electrochemical strain microscopy (ESM), and allows exploring the tip-induced electrochemical processes locally. Here we analyze the signal formation mechanism in ESM, and develop the analytical description of operation in frequency and time domains. The ESM spectroscopic modes are compared to classical electrochemical methods including potentiostatic and galvanostatic intermittent titration, and electrochemical impedance spectroscopy. This analysis illustrates the feasibility of spatially resolved studies of Li-ion dynamics on the sub-10-nm level using electromechanical detection.}, number={5}, journal={Journal of Applied Physics}, author={Morozovska, A. N. and Eliseev, E. A. and Balke, N. and Kalinin, S. V.}, year={2010} }
 @article{balke_jesse_morozovska_eliseev_chung_kim_adamczyk_garcia_dudney_kalinin_2010, title={Nanoscale mapping of ion diffusion in a lithium-ion battery cathode}, volume={5}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000282578000015&KeyUID=WOS:000282578000015}, DOI={10.1038/nnano.2010.174}, abstractNote={The movement of lithium ions into and out of electrodes is central to the operation of lithium-ion batteries. Although this process has been extensively studied at the device level, it remains insufficiently characterized at the nanoscale level of grain clusters, single grains and defects. Here, we probe the spatial variation of lithium-ion diffusion times in the battery-cathode material LiCoO(2) at a resolution of ∼100 nm by using an atomic force microscope to both redistribute lithium ions and measure the resulting cathode deformation. The relationship between diffusion and single grains and grain boundaries is observed, revealing that the diffusion coefficient increases for certain grain orientations and single-grain boundaries. This knowledge provides feedback to improve understanding of the nanoscale mechanisms underpinning lithium-ion battery operation.}, number={10}, journal={Nature Nanotechnology}, author={Balke, N. and Jesse, S. and Morozovska, A. N. and Eliseev, E. and Chung, D. W. and Kim, Y. and Adamczyk, L. and Garcia, R. E. and Dudney, N. and Kalinin, S. V.}, year={2010}, pages={749–754} }
 @article{balke_jesse_kim_adamczyk_tselev_ivanov_dudney_kalinin_2010, title={Real Space Mapping of Li-Ion Transport in Amorphous Si Anodes with Nanometer Resolution}, volume={10}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000281498200034&KeyUID=WOS:000281498200034}, DOI={10.1021/nl101439x}, abstractNote={The electrical bias driven Li-ion motion in silicon anode materials in thin film battery heterostructures is investigated using electrochemical strain microscopy (ESM), which is a newly developed scanning probe microscopy based characterization method. ESM utilizes the intrinsic link between bias-controlled Li-ion concentration and molar volume of electrode materials, providing the capability for studies on the sub-20 nm scale, and allows the relationship between Li-ion flow and microstructure to be established. The evolution of Li-ion transport during the battery charging is directly observed.}, number={9}, journal={Nano Letters}, author={Balke, Nina and Jesse, Stephen and Kim, Yoongu and Adamczyk, Leslie and Tselev, Alexander and Ivanov, Ilia N. and Dudney, Nancy J. and Kalinin, Sergei V.}, year={2010}, pages={3420–3425} }
 @article{seidel_martin_he_zhan_chu_rother_hawkridge_maksymovych_yu_gajek_et al._2009, title={Conduction at domain walls in oxide multiferroics}, volume={8}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000263556800023&KeyUID=WOS:000263556800023}, DOI={10.1038/nmat2373}, abstractNote={Domain walls may play an important role in future electronic devices, given their small size as well as the fact that their location can be controlled. Here, we report the observation of room-temperature electronic conductivity at ferroelectric domain walls in the insulating multiferroic BiFeO(3). The origin and nature of the observed conductivity are probed using a combination of conductive atomic force microscopy, high-resolution transmission electron microscopy and first-principles density functional computations. Our analyses indicate that the conductivity correlates with structurally driven changes in both the electrostatic potential and the local electronic structure, which shows a decrease in the bandgap at the domain wall. Additionally, we demonstrate the potential for device applications of such conducting nanoscale features.}, number={3}, journal={Nature Materials}, author={Seidel, J. and Martin, L. W. and He, Q. and Zhan, Q. and Chu, Y. H. and Rother, A. and Hawkridge, M. E. and Maksymovych, P. and Yu, P. and Gajek, M. and et al.}, year={2009}, pages={229–234} }
 @article{kalinin_rodriguez_borisevich_baddorf_balke_chang_chen_choudhury_jesse_maksymovych_et al._2010, title={Defect-Mediated Polarization Switching in Ferroelectrics and Related Materials: From Mesoscopic Mechanisms to Atomistic Control}, volume={22}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000274278500001&KeyUID=WOS:000274278500001}, DOI={10.1002/adma.200900813}, abstractNote={AbstractThe plethora of lattice and electronic behaviors in ferroelectric and multiferroic materials and heterostructures opens vistas into novel physical phenomena including magnetoelectric coupling and ferroelectric tunneling. The development of new classes of electronic, energy‐storage, and information‐technology devices depends critically on understanding and controlling field‐induced polarization switching. Polarization reversal is controlled by defects that determine activation energy, critical switching bias, and the selection between thermodynamically equivalent polarization states in multiaxial ferroelectrics. Understanding and controlling defect functionality in ferroelectric materials is as critical to the future of oxide electronics and solid‐state electrochemistry as defects in semiconductors are for semiconductor electronics. Here, recent advances in understanding the defect‐mediated switching mechanisms, enabled by recent advances in electron and scanning probe microscopy, are discussed. The synergy between local probes and structural methods offers a pathway to decipher deterministic polarization switching mechanisms on the level of a single atomically defined defect.}, number={3}, journal={Advanced Materials}, author={Kalinin, Sergei V. and Rodriguez, Brian J. and Borisevich, Albina Y. and Baddorf, Arthur P. and Balke, Nina and Chang, Hye Jung and Chen, Long-Qing and Choudhury, Samrat and Jesse, Stephen and Maksymovych, Peter and et al.}, year={2010}, pages={314–322} }
 @article{maksymovych_balke_jesse_huijben_ramesh_baddorf_kalinin_2009, title={Defect-induced asymmetry of local hysteresis loops on BiFeO3 surfaces}, volume={44}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000269117000006&KeyUID=WOS:000269117000006}, DOI={10.1007/s10853-009-3697-z}, abstractNote={Local piezoresponse hysteresis loops were systematically studied on the surface of ferroelectric thin films of BiFeO3 grown on SrRuO3 and La0.7Sr0.3MnO3 electrodes and compared between ultrahigh vacuum and ambient environment. The loops on all the samples exhibited characteristic asymmetry manifested in the difference of the piezoresponse slope following local domain nucleation. Spatially resolved mapping has revealed that the asymmetry is strongly correlated with the random-field disorder inherent in the films and is not affected by the random-bond disorder component. The asymmetry thus originates from electrostatic disorder within the film, which allows using it as a unique signature of single defects or defect clusters. The electrostatic effects due to the measurement environment also contribute to the total asymmetry of the piezoresponse loop, albeit with a much smaller magnitude compared to local defects.}, number={19}, journal={Journal of Materials Science}, author={Maksymovych, Peter and Balke, Nina and Jesse, Stephen and Huijben, Mark and Ramesh, Ramamoorthy and Baddorf, Arthur P. and Kalinin, Sergei V.}, year={2009}, pages={5095–5101} }
 @article{balke_granzow_roedel_2009, title={Degradation of lead-zirconate-titanate ceramics under different dc loads}, volume={105}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000266500100128&KeyUID=WOS:000266500100128}, DOI={10.1063/1.3126707}, abstractNote={During poling and application in actuators, piezoelectric ceramics like lead-zirconate-titanate are exposed to static or cyclically varying electric fields, often leading to pronounced changes in the electromechanical properties. These fatigue phenomena depend on time, peak electric load, and temperature. Although this process impacts the performance of many actuator materials, its physical understanding remains elusive. This paper proposes a set of key experiments to systematically investigate the changes in the ferroelectric hysteresis, field-dependent relative permittivity, and piezoelectric coefficient after submitting the material to dc loads of varying amplitude and duration. The observed effects are explained based on a model of domain stabilization due to charge accumulation at domain boundaries.}, number={10}, journal={Journal of Applied Physics}, author={Balke, Nina and Granzow, Torsten and Roedel, Juergen}, year={2009} }
 @article{balke_choudhury_jesse_huijben_chu_baddorf_chen_ramesh_kalinin_2009, title={Deterministic control of ferroelastic switching in multiferroic materials}, volume={4}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000272415600022&KeyUID=WOS:000272415600022}, DOI={10.1038/nnano.2009.293}, abstractNote={Multiferroic materials showing coupled electric, magnetic and elastic orderings provide a platform to explore complexity and new paradigms for memory and logic devices. Until now, the deterministic control of non-ferroelectric order parameters in multiferroics has been elusive. Here, we demonstrate deterministic ferroelastic switching in rhombohedral BiFeO(3) by domain nucleation with a scanning probe. We are able to select among final states that have the same electrostatic energy, but differ dramatically in elastic or magnetic order, by applying voltage to the probe while it is in lateral motion. We also demonstrate the controlled creation of a ferrotoroidal order parameter. The ability to control local elastic, magnetic and torroidal order parameters with an electric field will make it possible to probe local strain and magnetic ordering, and engineer various magnetoelectric, domain-wall-based and strain-coupled devices.}, number={12}, journal={Nature Nanotechnology}, author={Balke, N. and Choudhury, S. and Jesse, S. and Huijben, M. and Chu, Y. H. and Baddorf, A. P. and Chen, L. Q. and Ramesh, R. and Kalinin, S. V.}, year={2009}, pages={868–875} }
 @article{yang_seidel_kim_rossen_yu_gajek_chu_martin_holcomb_he_et al._2009, title={Electric modulation of conduction in multiferroic Ca-doped BiFeO3 films}, volume={8}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000266208700020&KeyUID=WOS:000266208700020}, DOI={10.1038/nmat2432}, abstractNote={Many interesting materials phenomena such as the emergence of high-Tc superconductivity in the cuprates and colossal magnetoresistance in the manganites arise out of a doping-driven competition between energetically similar ground states. Doped multiferroics present a tantalizing evolution of this generic concept of phase competition. Here, we present the observation of an electronic conductor-insulator transition by control of band-filling in the model antiferromagnetic ferroelectric BiFeO3 through Ca doping. Application of electric field enables us to control and manipulate this electronic transition to the extent that a p-n junction can be created, erased and inverted in this material. A 'dome-like' feature in the doping dependence of the ferroelectric transition is observed around a Ca concentration of approximately 1/8, where a new pseudo-tetragonal phase appears and the electric modulation of conduction is optimized. Possible mechanisms for the observed effects are discussed on the basis of the interplay of ionic and electronic conduction. This observation opens the door to merging magnetoelectrics and magnetoelectronics at room temperature by combining electronic conduction with electric and magnetic degrees of freedom already present in the multiferroic BiFeO3.}, number={6}, journal={Nature Materials}, author={Yang, C. H. and Seidel, J. and Kim, S. Y. and Rossen, P. B. and Yu, P. and Gajek, M. and Chu, Y. H. and Martin, L. W. and Holcomb, M. B. and He, Q. and et al.}, year={2009}, pages={485–493} }
 @article{balke_bdikin_kalinin_kholkin_2009, title={Electromechanical Imaging and Spectroscopy of Ferroelectric and Piezoelectric Materials: State of the Art and Prospects for the Future}, volume={92}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000268704600001&KeyUID=WOS:000268704600001}, DOI={10.1111/j.1551-2916.2009.03240.x}, abstractNote={Piezoresponse force microscopy (PFM) has emerged as a powerful and versatile tool for probing nanoscale phenomena in ferroelectric materials on the nanometer and micrometer scales. In this review, we summarize the fundamentals and recent advances in PFM, and describe the nanoscale electromechanical properties of several important ferroelectric ceramic materials widely used in memory and microelectromechanical systems applications. Probing static and dynamic polarization behavior of individual grains in PZT films and ceramics is discussed. Switching spectroscopy PFM is introduced as a useful tool for studying defects and interfaces in ceramic materials. The results on local switching and domain pinning behavior, as well as nanoscale fatigue and imprint mapping are presented. Probing domain structures and polarization dynamics in polycrystalline relaxors (PMN‐PT, PLZT, doped BaTiO3) are briefly outlined. Finally, applications of PFM to dimensionally confined ferroelectrics are demonstrated. The potential of PFM for studying local electromechanical phenomena in polycrystalline ferroelectrics where defects and other inhomogeneities are essential for the interpretation of their macroscopic properties is illustrated.}, number={8}, journal={Journal of the American Ceramic Society}, author={Balke, Nina and Bdikin, Igor and Kalinin, Sergei V. and Kholkin, Andrei L.}, year={2009}, pages={1629–1647} }
 @article{chang_borisevich_balke_kalinin_ramesh_huijben_pennycook_2009, title={Interfacial Structure in Multiferroic BiFeO3 Thin Films}, volume={15}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000208119100508&KeyUID=WOS:000208119100508}, DOI={10.1017/s1431927609092903}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009}, journal={Microscopy and Microanalysis}, author={Chang, H. J. and Borisevich, A. Y. and Balke, N. and Kalinin, S. V. and Ramesh, R. and Huijben, M. and Pennycook, S. J.}, year={2009}, pages={1028–1029} }
 @inbook{balke_yu_wang_ramesh_ieee_2008, title={CH003: Stability of nanodots in ferroelectric thin films}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270584000022&KeyUID=WOS:000270584000022}, booktitle={2008 17th Ieee International Symposium on the Applications of Ferroelectrics}, author={Balke, N. and Yu, P. and Wang, L. P. and Ramesh, R. and Ieee}, year={2008}, pages={69–70} }
 @inbook{balke_granzow_roedel_ieee_2008, title={CHO15: Current-voltage characteristics for PZT ceramics}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270584000031&KeyUID=WOS:000270584000031}, booktitle={2008 17th Ieee International Symposium on the Applications of Ferroelectrics}, author={Balke, N. and Granzow, T. and Roedel, J. and Ieee}, year={2008}, pages={91–92} }
 @article{balke_granzow_roedel_2008, title={Current-voltage characteristics for lead zirconate titanate bulk ceramics}, volume={104}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000259853600106&KeyUID=WOS:000259853600106}, DOI={10.1063/1.2976304}, abstractNote={Current-voltage characteristics have been obtained on lead zirconate titanate bulk ceramics using robust measurement techniques separating polarization effects from actual charge transport. Measurement of the electrical conduction upon both increase and decrease in the electric field shows that long settling times are required to suppress polarization currents and obtain reliable data. The influence of additional field cycles and different electrode materials is also studied. The analysis reveals that an Ohmic conduction is dominant at low fields, while at high fields charge transport is most likely governed by space charge limited currents.}, number={5}, journal={Journal of Applied Physics}, author={Balke, Nina and Granzow, Torsten and Roedel, Juergen}, year={2008} }
 @article{chu_martin_holcomb_gajek_han_he_balke_yang_lee_hu_et al._2008, title={Electric-field control of local ferromagnetism using a magnetoelectric multiferroic}, volume={7}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000256110200022&KeyUID=WOS:000256110200022}, DOI={10.1038/nmat2184}, abstractNote={Multiferroics are of interest for memory and logic device applications, as the coupling between ferroelectric and magnetic properties enables the dynamic interaction between these order parameters. Here, we report an approach to control and switch local ferromagnetism with an electric field using multiferroics. We use two types of electromagnetic coupling phenomenon that are manifested in heterostructures consisting of a ferromagnet in intimate contact with the multiferroic BiFeO(3). The first is an internal, magnetoelectric coupling between antiferromagnetism and ferroelectricity in the BiFeO(3) film that leads to electric-field control of the antiferromagnetic order. The second is based on exchange interactions at the interface between a ferromagnet (Co(0.9)Fe(0.1)) and the antiferromagnet. We have discovered a one-to-one mapping of the ferroelectric and ferromagnetic domains, mediated by the colinear coupling between the magnetization in the ferromagnet and the projection of the antiferromagnetic order in the multiferroic. Our preliminary experiments reveal the possibility to locally control ferromagnetism with an electric field.}, number={6}, journal={Nature Materials}, author={Chu, Ying-Hao and Martin, Lane W. and Holcomb, Mikel B. and Gajek, Martin and Han, Shu-Jen and He, Qing and Balke, Nina and Yang, Chan-Ho and Lee, Donkoun and Hu, Wei and et al.}, year={2008}, pages={478–482} }
 @article{chu_martin_holcomb_gajek_han_he_balke_yang_lee_hu_et al._2008, title={Electric-field control of local ferromagnetism using a magnetoelectric multiferroic (vol 7, pg 478, 2008)}, volume={7}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000257892200029&KeyUID=WOS:000257892200029}, DOI={10.1038/nmat2246}, abstractNote={Nature Materials 7, 478–482 (2008) The authors wish to correct Fig. 6 of this article, where they had incorrectly depicted the incoming X-ray direction; this does not alter the interpretation of the data presented. The correct figure is shown below.}, number={8}, journal={Nature Materials}, author={Chu, Ying-Hao and Martin, Lane W. and Holcomb, Mikel B. and Gajek, Martin and Han, Shu-Jen and He, Qing and Balke, Nina and Yang, Chan-Ho and Lee, Donkoun and Hu, Wei and et al.}, year={2008}, pages={678} }
 @article{genenko_balke_lupascu_2008, title={Migration of Charged Defects in Local Depolarization Fields as a Mechanism of Aging in Ferroelectrics}, volume={370}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000260641100025&KeyUID=WOS:000260641100025}, DOI={10.1080/00150190802381563}, abstractNote={Quasistatic dielectric relaxation due to migration of charged point defects is considered as a mechanism of aging in ferroelectrics. A two-dimensional model is developed which includes the coupled potential problem and the field-driven diffusion problem. Numerical study reveals formation of space charge zones near the grain boundaries with the only characteristic time of several days being the Maxwell relaxation time defined by the charge carrier density and mobility. The clamping pressure due to charge segregation is about few MPa which corresponds to observed coercive stresses in perovskite ferroelectrics and is significantly stronger than in the mechanisms involving orientational reordering of defect dipoles.}, journal={Ferroelectrics}, author={Genenko, Y. A. and Balke, N. and Lupascu, D. C.}, year={2008}, pages={196–202} }
 @article{martin_crane_chu_holcomb_gajek_huijben_yang_balke_ramesh_2008, title={Multiferroics and magnetoelectrics: thin films and nanostructures}, volume={20}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000259922600021&KeyUID=WOS:000259922600021}, DOI={10.1088/0953-8984/20/43/434220}, abstractNote={Multiferroic materials, or materials that simultaneously possess two or more ferroic order parameters, have returned to the forefront of materials research. Driven by the desire to achieve new functionalities—such as electrical control of ferromagnetism at room temperature—researchers have undertaken a concerted effort to identify and understand the complexities of multiferroic materials. The ability to create high quality thin film multiferroics stands as one of the single most important landmarks in this flurry of research activity. In this review we discuss the basics of multiferroics including the important order parameters and magnetoelectric coupling in materials. We then discuss in detail the growth of single phase, horizontal multilayer, and vertical heterostructure multiferroics. The review ends with a look to the future and how multiferroics can be used to create new functionalities in materials.}, number={43}, journal={Journal of Physics-Condensed Matter}, author={Martin, L. W. and Crane, S. P. and Chu, Y. H. and Holcomb, M. B. and Gajek, M. and Huijben, M. and Yang, C. H. and Balke, N. and Ramesh, R.}, year={2008} }
 @inbook{genenko_balke_lupascu_ieee_2007, title={Aging in Ferroelectrics, a Drift Approach}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000262360900070&KeyUID=WOS:000262360900070}, booktitle={2006 15th IEEE International Symposium on Applications of Ferroelectrics}, author={Genenko, Yuri and Balke, Nina and Lupascu, Doru C. and Ieee}, year={2007}, pages={290–293} }
 @article{balke_kungl_granzow_lupascu_hoffmann_rodel_2007, title={Bipolar fatigue caused by field screening in Pb(Zr,Ti)O-3 ceramics}, volume={90}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000251504300023&KeyUID=WOS:000251504300023}, DOI={10.1111/j.1551-2916.2007.02041.x}, abstractNote={ Bipolar cycling of lead zirconate titanate ceramics can lead to massive material damage in regions close to the electrode. The damaged region can be identified by color changes, and the microstructure in this region shows signs of interface melting. This damaged region can screen the sample volume from the applied voltages and reduced fields are applied to the undamaged part of the sample. This has two effects. The first one is that the bulk is effectively subjected to smaller fields, but the measured parameters are assigned to the applied field, yielding apparent fatigue curves. The second effect is that with further cycling, field screening protects the bulk of the sample from fatigue due to the reduced effective fields. If the damaged region is mechanically removed and the ferroelectric hystereses are measured again, nearly unfatigued parameters are obtained. }, number={12}, journal={Journal of the American Ceramic Society}, author={Balke, Nina and Kungl, Hans and Granzow, Torsten and Lupascu, Doru C. and Hoffmann, Michael J. and Rodel, Jurgen}, year={2007}, pages={3869–3874} }
 @inbook{puff_balke_kungl_hoffmann_balogh_2007, title={Effect of Fe-doping and electrical load on the defect structure of Pb(ZrxTi1-x)O-3 ferroelectric ceramics}, volume={4}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000250716700094&KeyUID=WOS:000250716700094}, DOI={10.1002/pssc.200675863}, abstractNote={AbstractVacancy related defects in undoped and 1 mol% Fe doped Pb(Zr54Ti46)O3 ferroelectric ceramic samples have been investigated by means of positron lifetime spectroscopy. Temperature dependent measure‐ments between 10 K and room temperature have been performed to study the influence of the acceptor type doping on the defect structure and on the charge states of the defects. On commercial Pb(Zr0.54Ti0.47(Ni0.33Sb0.67)0.08)O3 samples the influence of different electrical loading have been studied. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)}, booktitle={Physica Status Solidi C - Current Topics in Solid State Physics, Vol 4, No 10}, author={Puff, W. and Balke, N. and Kungl, H. and Hoffmann, M. J. and Balogh, A. G.}, editor={Knights, A. P. and Mascher, P. and Simpson, P. J.Editors}, year={2007}, pages={3839–3842} }
 @article{balke_lupascu_granzow_roedel_2007, title={Fatigue of lead zirconate titanate ceramics II: Sesquipolar loading}, volume={90}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000245675300012&KeyUID=WOS:000245675300012}, DOI={10.1111/j.1551-2916.2007.01521.x}, abstractNote={ Piezoelectric actuators generally are driven with unipolar electric load cycles. Although the obtainable strain is increased by small excursions into the negative field regime, this type of load cycle is rarely considered, as its long‐time reliability has been questioned. Here, we investigate the degradation of lead zirconate titanate during cycling between high positive and low negative electric fields. Measurements of the large and small signal parameters are used to quantify changes of the material. The fatigue behavior shifts from one best described with existing models of unipolar fatigue to bipolar‐like fatigue with increasing field amplitude. }, number={4}, journal={Journal of the American Ceramic Society}, author={Balke, Nina and Lupascu, Doru C. and Granzow, Torsten and Roedel, Juergen}, year={2007}, pages={1088–1093} }
 @article{balke_lupascu_granzow_roedel_2007, title={Fatigue of lead zirconate titanate ceramics. I: Unipolar and DC loading}, volume={90}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000245675300011&KeyUID=WOS:000245675300011}, DOI={10.1111/j.1551-2916.2007.01520.x}, abstractNote={ In actuator applications, a degradation of the ferroelectric material occurs both under unipolar cycling as well as DC loads. The developing material state is characterized by measurements of large and small signal unipolar as well as bipolar hysteresis loops. While the unipolar loops indicate a small decrease in strain and polarization amplitudes, the bipolar loops unveil the development of an offset field, an offset polarization, and an asymmetry in the hysteresis of strain and dielectric constant. A mechanism for unipolar fatigue is suggested to explain the observed changes in material properties with cyclic loading. }, number={4}, journal={Journal of the American Ceramic Society}, author={Balke, Nina and Lupascu, Doru C. and Granzow, Torsten and Roedel, Juergen}, year={2007}, pages={1081–1087} }
 @inbook{roedel_balke_glaum_granzow_ieee_2007, title={Unipolar and sesquipolar electrical fatigue in PZT}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000253416100198&KeyUID=WOS:000253416100198}, booktitle={2007 Sixteenth Ieee International Symposium on the Applications of Ferroelectrics, Vols 1 and 2}, author={Roedel, Juergen and Balke, Nina and Glaum, Julia and Granzow, Torsten and Ieee}, year={2007}, pages={602–604} }
 @article{balke_lupascu_blair_gruverman_2006, title={Thickness profiles through fatigued bulk ceramic lead zirconate titanate}, volume={100}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000242887400130&KeyUID=WOS:000242887400130}, DOI={10.1063/1.2395600}, abstractNote={Wedge-cut samples of fatigued ferroelectric lead zirconate titanate ceramics were investigated using piezoresponse force microscopy in conjunction with conventional electrical hysteresis measurements. The local clamping of domains is monitored at different depths in the sample. The coercive fields in grains near the electrodes differ for different materials and preparation methods of the electrodes. For silver, fatigue consistently generates a space charge in the depth of the sample. For platinum electrodes, the fatigue behavior scatters strongly. Microscopically, it either occurs directly underneath the electrodes or resembles the behavior of the silver electrodes in other samples.}, number={11}, journal={Journal of Applied Physics}, author={Balke, Nina and Lupascu, Doru C. and Blair, Thomas and Gruverman, Alexei}, year={2006} }
 @article{lupascu_genenko_balke_2006, title={Aging in ferroelectrics}, volume={89}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000234482600034&KeyUID=WOS:000234482600034}, DOI={10.1111/j.1551-2916.2005.00663.x}, abstractNote={ The reorientation of defect dipoles and the drift of free charge carriers are the most prominent microscopic mechanisms under discussion to provoke the aging effect in ferroelectrics. These two mechanisms are contrasted taking into account the influence of grain boundaries in a polycrystalline material. For the drift model, clamping pressures on domain walls only depend on geometry and on the transport properties of the mobile defect charge carrier independent of its electronic or ionic nature. For a numerical example clamping pressures as a result of drift of oxygen vacancies are determined in BaTiO3. They range from 106 to 107 Pa corresponding to experimental values. }, number={1}, journal={Journal of the American Ceramic Society}, author={Lupascu, D. C. and Genenko, Y. A. and Balke, N.}, year={2006}, pages={224–229} }
 @article{granzow_balke_lupascu_rodel_2005, title={Evolution of a stable polarization state in lead zirconate titanate ceramics by repeated partial switching}, volume={87}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000233362300058&KeyUID=WOS:000233362300058}, DOI={10.1063/1.2133930}, abstractNote={The development of the ferroelectric polarization of lead–zirconate–titanate (PZT) bulk ceramics under varying electric fields is examined. Repeated partial switching and backswitching results in a decrease of the switchable polarization, but has no effect on the effective strain. This is attributed to a stabilization of the domain structure, which leads to a decrease of the electric losses. The results are discussed with respect to the effective strain of PZT ceramics for piezoelectric actuators.}, number={21}, journal={Applied Physics Letters}, author={Granzow, T. and Balke, N. and Lupascu, D. C. and Rodel, J.}, year={2005} }
 @article{zhang_lupascu_balke_rodel_2005, title={Near electrode fatigue in lead zirconate titanate ceramics}, volume={128}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000232430400016&KeyUID=WOS:000232430400016}, DOI={10.1051/jp4:2005128015}, abstractNote={Fatigue in ferroelectric materials is partly due to a complex interplay of ferroelectric ceramic and electrode material. Different types of silver electrodes were tested for their effect on fatigue. Material damage mostly occurs in the near-electrode volume. Removal of material to different depths from the electrode yields different degrees of recovery of device properties depending on electrode material and cycle number. Polarization hysteresis, time resolved switching, and small signal dielectric and piezoelectric measurements are equally affected.}, journal={Journal De Physique Iv}, author={Zhang, Y. and Lupascu, D. C. and Balke, N. and Rodel, J.}, year={2005}, pages={97–103} }