@article{moatti_connard_de britto_dunn_rastogi_rai_schnabel_ligler_hutson_fitzpatrick_et al._2024, title={Surgical procedure of intratympanic injection and inner ear pharmacokinetics simulation in domestic pigs}, volume={15}, ISSN={["1663-9812"]}, DOI={10.3389/fphar.2024.1348172}, abstractNote={Introduction: One major obstacle in validating drugs for the treatment or prevention of hearing loss is the limited data available on the distribution and concentration of drugs in the human inner ear. Although small animal models offer some insights into inner ear pharmacokinetics, their smaller organ size and different barrier (round window membrane) permeabilities compared to humans can complicate study interpretation. Therefore, developing a reliable large animal model for inner ear drug delivery is crucial. The inner and middle ear anatomy of domestic pigs closely resembles that of humans, making them promising candidates for studying inner ear pharmacokinetics. However, unlike humans, the anatomical orientation and tortuosity of the porcine external ear canal frustrates local drug delivery to the inner ear. Methods: In this study, we developed a surgical technique to access the tympanic membrane of pigs. To assess hearing pre- and post-surgery, auditory brainstem responses to click and pure tones were measured. Additionally, we performed 3D segmentation of the porcine inner ear images and used this data to simulate the diffusion of dexamethasone within the inner ear through fluid simulation software (FluidSim). Results: We have successfully delivered dexamethasone and dexamethasone sodium phosphate to the porcine inner ear via the intratympanic injection. The recorded auditory brainstem measurements revealed no adverse effects on hearing thresholds attributable to the surgery. We have also simulated the diffusion rates for dexamethasone and dexamethasone sodium phosphate into the porcine inner ear and confirmed the accuracy of the simulations using in-vivo data. Discussion: We have developed and characterized a method for conducting pharmacokinetic studies of the inner ear using pigs. This animal model closely mirrors the size of the human cochlea and the thickness of its barriers. The diffusion time and drug concentrations we reported align closely with the limited data available from human studies. Therefore, we have demonstrated the potential of using pigs as a large animal model for studying inner ear pharmacokinetics.}, journal={FRONTIERS IN PHARMACOLOGY}, author={Moatti, Adele and Connard, Shannon and De Britto, Novietta and Dunn, William A. and Rastogi, Srishti and Rai, Mani and Schnabel, Lauren V. and Ligler, Frances S. and Hutson, Kendall A. and Fitzpatrick, Douglas C. and et al.}, year={2024}, month={Jan} }
 @article{moatti_silkstone_martin_abbey_hutson_fitzpatrick_zdanski_cheng_ligler_greenbaum_2023, title={Assessment of drug permeability through an ex vivo porcine round window membrane model}, volume={26}, ISSN={["2589-0042"]}, DOI={10.1016/j.isci.2023.106789}, abstractNote={Delivery of pharmaceutical therapeutics to the inner ear to treat and prevent hearing loss is challenging. Systemic delivery is not effective as only a small fraction of the therapeutic agent reaches the inner ear. Invasive surgeries to inject through the round window membrane (RWM) or cochleostomy may cause damage to the inner ear. An alternative approach is to administer drugs into the middle ear using an intratympanic injection, with the drugs primarily passing through the RWM to the inner ear. However, the RWM is a barrier, only permeable to a small number of molecules. To study and enhance the RWM permeability, we developed an ex vivo porcine RWM model, similar in structure and thickness to the human RWM. The model is viable for days, and drug passage can be measured at multiple time points. This model provides a straightforward approach to developing effective and non-invasive delivery methods to the inner ear.}, number={6}, journal={ISCIENCE}, author={Moatti, Adele and Silkstone, Dylan and Martin, Taylor and Abbey, Keith and Hutson, Kendall A. and Fitzpatrick, Douglas C. and Zdanski, Carlton J. and Cheng, Alan G. and Ligler, Frances S. and Greenbaum, Alon}, year={2023}, month={Jun} }
 @article{moatti_cai_li_popowski_cheng_ligler_greenbaum_2023, title={Tissue clearing and three-dimensional imaging of the whole cochlea and vestibular system from multiple large-animal models}, volume={4}, ISSN={["2666-1667"]}, DOI={10.1016/j.xpro.2023.102220}, abstractNote={The inner ear of humans and large animals is embedded in a thick and dense bone that makes dissection challenging. Here, we present a protocol that enables three-dimensional (3D) characterization of intact inner ears from large-animal models. We describe steps for decalcifying bone, using solvents to remove color and lipids, and imaging tissues in 3D using confocal and light sheet microscopy. We then detail a pipeline to count hair cells in antibody-stained and 3D imaged cochleae using open-source software. For complete details on the use and execution of this protocol, please refer to (Moatti et al., 2022).1.}, number={2}, journal={STAR PROTOCOLS}, author={Moatti, Adele and Cai, Yuheng and Li, Chen and Popowski, Kristen D. and Cheng, Ke and Ligler, Frances S. and Greenbaum, Alon}, year={2023}, month={Jun} }
 @article{li_moatti_zhang_ghashghaei_greenbaum_2022, title={Deep learning-based autofocus method enhances image quality in light-sheet fluorescence microscopy: publishers note (vol 12, pg 5214, 2021)}, volume={13}, ISSN={["2156-7085"]}, DOI={10.1364/BOE.450829}, abstractNote={[This corrects the article on p. 5214 in vol. 12, PMID: 34513252.].}, number={1}, journal={BIOMEDICAL OPTICS EXPRESS}, author={LI, Chen and Moatti, Adele and Zhang, Xuying and Ghashghaei, H. Troy and Greenbaum, Alon}, year={2022}, month={Jan}, pages={373–373} }
 @article{popowski_moatti_scull_silkstone_lutz_lópez de juan abad_george_belcher_zhu_mei_et al._2022, title={Inhalable dry powder mRNA vaccines based on extracellular vesicles}, volume={5}, ISSN={2590-2385}, url={http://dx.doi.org/10.1016/j.matt.2022.06.012}, DOI={10.1016/j.matt.2022.06.012}, abstractNote={Respiratory diseases are a global burden, with millions of deaths attributed to pulmonary illnesses and dysfunctions. Therapeutics have been developed, but they present major limitations regarding pulmonary bioavailability and product stability. To circumvent such limitations, we developed room-temperature-stable inhalable lung-derived extracellular vesicles or exosomes (Lung-Exos) as mRNA and protein drug carriers. Compared with standard synthetic nanoparticle liposomes (Lipos), Lung-Exos exhibited superior distribution to the bronchioles and parenchyma and are deliverable to the lungs of rodents and nonhuman primates (NHPs) by dry powder inhalation. In a vaccine application, severe acute respiratory coronavirus 2 (SARS-CoV-2) spike (S) protein encoding mRNA-loaded Lung-Exos (S-Exos) elicited greater immunoglobulin G (IgG) and secretory IgA (SIgA) responses than its loaded liposome (S-Lipo) counterpart. Importantly, S-Exos remained functional at room-temperature storage for one month. Our results suggest that extracellular vesicles can serve as an inhaled mRNA drug-delivery system that is superior to synthetic liposomes.}, number={9}, journal={Matter}, publisher={Elsevier BV}, author={Popowski, Kristen D. and Moatti, Adele and Scull, Grant and Silkstone, Dylan and Lutz, Halle and López de Juan Abad, Blanca and George, Arianna and Belcher, Elizabeth and Zhu, Dashuai and Mei, Xuan and et al.}, year={2022}, month={Sep}, pages={2960–2974} }
 @article{moatti_li_sivadanam_cai_ranta_piedrahita_cheng_ligler_greenbaum_2022, title={Ontogeny of cellular organization and LGR5 expression in porcine cochlea revealed using tissue clearing and 3D imaging}, volume={25}, ISSN={["2589-0042"]}, DOI={10.1016/j.isci.2022.104695}, abstractNote={Over 11% of the world's population experience hearing loss. Although there are promising studies to restore hearing in rodent models, the size, ontogeny, genetics, and frequency range of hearing of most rodents' cochlea do not match that of humans. The porcine cochlea can bridge this gap as it shares many anatomical, physiological, and genetic similarities with its human counterpart. Here, we provide a detailed methodology to process and image the porcine cochlea in 3D using tissue clearing and light-sheet microscopy. The resulting 3D images can be employed to compare cochleae across different ages and conditions, investigate the ontogeny of cochlear cytoarchitecture, and produce quantitative expression maps of LGR5, a marker of cochlear progenitors in mice. These data reveal that hair cell organization, inner ear morphology, cellular cartography in the organ of Corti, and spatiotemporal expression of LGR5 are dynamic over developmental stages in a pattern not previously documented.}, number={8}, journal={ISCIENCE}, author={Moatti, Adele and Li, Chen and Sivadanam, Sasank and Cai, Yuheng and Ranta, James and Piedrahita, Jorge A. and Cheng, Alan G. and Ligler, Frances S. and Greenbaum, Alon}, year={2022}, month={Aug} }
 @article{moatti_mineo-foley_gupta_sachan_narayan_2022, title={Spin Engineering of VO2 Phase Transitions and Removal of Structural Transition}, volume={14}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.1c24978}, DOI={10.1021/acsami.1c24978}, abstractNote={Vanadium dioxide undergoes a metal-to-insulator transition, where the energy of electron-electron, electron-lattice, spin-spin, and spin-lattice interactions are of the same order of magnitude. This leads to the coexistence of electronic and structural transitions in VO2 that limit the lifetime and speed of VO2-based devices. However, the closeness of interaction energy of lattice-electron-spin can be turned into an opportunity to induce some transitions while pinning others via external stimuli. That is, the contribution of spin, charge, orbital, and lattice degrees of freedom can be manipulated. In this study, spin engineering has been exploited to affect the spin-related interactions in VO2 by introducing a ferromagnetic Ni layer. The coercivity in the Ni layer is engineered by controlling the shape anisotropy via kinetics of growth. Using spin engineering, the structural pinning of the monoclinic M2 phase of VO2 is successfully achieved, while the electronic and magnetic transitions take place.}, number={10}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Moatti, Adele and Mineo-Foley, Gabrielle and Gupta, Siddharth and Sachan, Ritesh and Narayan, Jay}, year={2022}, month={Mar}, pages={12883–12892} }
 @article{li_moatti_zhang_ghashghaei_greenabum_2021, title={Deep learning-based autofocus method enhances image quality in light-sheet fluorescence microscopy}, volume={12}, ISSN={["2156-7085"]}, url={http://dx.doi.org/10.1364/boe.427099}, DOI={10.1364/BOE.427099}, abstractNote={Light-sheet fluorescence microscopy (LSFM) is a minimally invasive and high throughput imaging technique ideal for capturing large volumes of tissue with sub-cellular resolution. A fundamental requirement for LSFM is a seamless overlap of the light-sheet that excites a selective plane in the specimen, with the focal plane of the objective lens. However, spatial heterogeneity in the refractive index of the specimen often results in violation of this requirement when imaging deep in the tissue. To address this issue, autofocus methods are commonly used to refocus the focal plane of the objective-lens on the light-sheet. Yet, autofocus techniques are slow since they require capturing a stack of images and tend to fail in the presence of spherical aberrations that dominate volume imaging. To address these issues, we present a deep learning-based autofocus framework that can estimate the position of the objective-lens focal plane relative to the light-sheet, based on two defocused images. This approach outperforms or provides comparable results with the best traditional autofocus method on small and large image patches respectively. When the trained network is integrated with a custom-built LSFM, a certainty measure is used to further refine the network's prediction. The network performance is demonstrated in real-time on cleared genetically labeled mouse forebrain and pig cochleae samples. Our study provides a framework that could improve light-sheet microscopy and its application toward imaging large 3D specimens with high spatial resolution.}, number={8}, journal={BIOMEDICAL OPTICS EXPRESS}, publisher={The Optical Society}, author={Li, Chen and Moatti, Adele and Zhang, Xuying and Ghashghaei, H. Troy and Greenabum, Alon}, year={2021}, month={Aug}, pages={5214–5226} }
 @article{carter_popowski_cheng_greenbaum_ligler_moatti_2021, title={Enhancement of Bone Regeneration Through the Converse Piezoelectric Effect, A Novel Approach for Applying Mechanical Stimulation}, volume={9}, ISSN={["2576-3113"]}, url={https://doi.org/10.1089/bioe.2021.0019}, DOI={10.1089/bioe.2021.0019}, abstractNote={Serious bone injuries have devastating effects on the lives of patients including limiting working ability and high cost. Orthopedic implants can aid in healing injuries to an extent that exceeds the natural regenerative capabilities of bone to repair fractures or large bone defects. Autografts and allografts are the standard implants used, but disadvantages such as donor site complications, a limited quantity of transplantable bone, and high costs have led to an increased demand for synthetic bone graft substitutes. However, replicating the complex physiological properties of biological bone, much less recapitulating its complex tissue functions, is challenging. Extensive efforts to design biocompatible implants that mimic the natural healing processes in bone have led to the investigation of piezoelectric smart materials because the bone has natural piezoelectric properties. Piezoelectric materials facilitate bone regeneration either by accumulating electric charge in response to mechanical stress, which mimics bioelectric signals through the direct piezoelectric effect or by providing mechanical stimulation in response to electrical stimulation through the converse piezoelectric effect. Although both effects are beneficial, the converse piezoelectric effect can address bone atrophy from stress shielding and immobility by improving the mechanical response of a healing defect. Mechanical stimulation has a positive impact on bone regeneration by activating cellular pathways that increase bone formation and decrease bone resorption. This review will highlight the potential of the converse piezoelectric effect to enhance bone regeneration by discussing the activation of beneficial cellular pathways, the properties of piezoelectric biomaterials, and the potential for the more effective administration of the converse piezoelectric effect using wireless control.}, journal={BIOELECTRICITY}, publisher={Mary Ann Liebert Inc}, author={Carter, Amber and Popowski, Kristen and Cheng, Ke and Greenbaum, Alon and Ligler, Frances S. and Moatti, Adele}, year={2021}, month={Sep} }
 @article{moatti_sachan_narayan_2020, title={Mechanism of strain relaxation: key to control of structural and electronic transitions in VO2 thin-films}, url={https://doi.org/10.1080/21663831.2019.1681030}, DOI={10.1080/21663831.2019.1681030}, abstractNote={VO2 is a smart transition-metal oxide, which exhibits a tetragonal-to-monoclinic phase transition at ∼ 68°C. We report a case where both tetragonal and monoclinic phases exist in relaxed and strained domains, respectively, above the transition temperature. The epitaxial nucleation of these relaxed domains of VO2 over the strained one occurs when the critical thickness criterion is met through the emergence of interfacial dislocations under domain-matching epitaxy paradigm. Below this critical thickness, the film isostructurally (across the transition temperature range) adopts a strained-monoclinic phase. Above the critical thickness, domains are structurally free to transform from tetragonal to monoclinic. GRAPHICAL ABSTRACT Impact statement We studied formation and atomic-scale characterization of a novel heterostructure of relaxed (tetragonal/monoclinic) and unrelaxed (monoclinic) VO2 phases. The monoclinic-to-tetragonal structural transition occurs at the critical thickness of ∼15 nm.}, journal={Materials Research Letters}, author={Moatti, Adele and Sachan, Ritesh and Narayan, Jagdish}, year={2020}, month={Jan} }
 @article{moatti_cai_li_sattler_edwards_piedrahita_ligler_greenbaum_2020, title={Three-dimensional imaging of intact porcine cochlea using tissue clearing and custom-built light-sheet microscopy}, volume={11}, ISSN={["2156-7085"]}, url={http://dx.doi.org/10.1364/boe.402991}, DOI={10.1364/BOE.402991}, abstractNote={Hearing loss is a prevalent disorder that affects people of all ages. On top of the existing hearing aids and cochlear implants, there is a growing effort to regenerate functional tissues and restore hearing. However, studying and evaluating these regenerative medicine approaches in a big animal model (e.g. pigs) whose anatomy, physiology, and organ size are similar to a human is challenging. In big animal models, the cochlea is bulky, intricate, and veiled in a dense and craggy otic capsule. These facts complicate 3D microscopic analysis that is vital in the cochlea, where structure-function relation is time and again manifested. To allow 3D imaging of an intact cochlea of newborn and juvenile pigs with a volume up to ∼ 250 mm3, we adapted the BoneClear tissue clearing technique, which renders the bone transparent. The transparent cochleae were then imaged with cellular resolution and in a timely fashion, which prevented bubble formation and tissue degradation, using an adaptive custom-built light-sheet fluorescence microscope. The adaptive light-sheet microscope compensated for deflections of the illumination beam by changing the angles of the beam and translating the detection objective while acquiring images. Using this combination of techniques, macroscopic and microscopic properties of the cochlea were extracted, including the density of hair cells, frequency maps, and lower frequency limits. Consequently, the proposed platform could support the growing effort to regenerate cochlear tissues and assist with basic research to advance cures for hearing impairments.}, number={11}, journal={BIOMEDICAL OPTICS EXPRESS}, publisher={The Optical Society}, author={Moatti, Adele and Cai, Yuheng and Li, Chen and Sattler, Tyler and Edwards, Laura and Piedrahita, Jorge and Ligler, Frances S. and Greenbaum, Alon}, year={2020}, month={Nov}, pages={6181–6196} }
 @article{moatti_sachan_narayan_2020, title={Volatile and non-volatile behavior of metal–insulator transition in VO2 through oxygen vacancies tunability for memory applications}, url={https://doi.org/10.1063/5.0006671}, DOI={10.1063/5.0006671}, abstractNote={Vanadium dioxide can be utilized as a Mott memory, where “0” and “1” states can be defined by insulator and metal states, respectively. In stoichiometric VO2, voltage or joule heating can trigger the transition and activate the volatile behavior. As a result, there is a constant need for such a stimulus to preserve the “1” state. If oxygen vacancies are introduced to the system while maintaining the crystal structure of the VO2 phase, the state “1” can be obtained/written permanently. That is, there is no need for external stimuli to read and recall the data. Here, we have shown the reversibility of the behavior and structure of the VO2 when oxygen vacancies are introduced to and removed from the system. The structure and relaxation mechanism are discussed, as well. This research paves the way for the nonvolatile application of VO2 in neuromorphic devices.}, journal={Journal of Applied Physics}, author={Moatti, Adele and Sachan, Ritesh and Narayan, Jagdish}, year={2020}, month={Jul} }
 @article{moatti_sachan_kumar_narayan_2019, title={Catalyst-assisted epitaxial growth of ferromagnetic TiO2/TiN nanowires}, volume={167}, ISSN={1359-6454}, url={http://dx.doi.org/10.1016/J.ACTAMAT.2019.01.052}, DOI={10.1016/j.actamat.2019.01.052}, abstractNote={We report a novel method of growth for single-crystalline TiO2/TiN nanowires through oxidation of epitaxial TiN nanowires on Si-SiO2 (amorphous) and c-sapphire (crystalline) as practical substrates. We propose that the laser ablated Ti and N diffuse into molten Au to form TiN nanodots where the growth rate of nanowires is directly proportional to the laser ablation flux due to high diffusion in molten Au. The TiN nanowires were grown by Pulsed Laser Deposition method using Au as a catalyst. The TiN nanowires were then oxidized to create TiO2/TiN core-shell nanowires. The growth of TiO2 (rutile) occurs by domain matching epitaxy paradigm in such a way that (002) planes of the TiO2 match with (200) plane of TiN, where the TiO2 thickness can be tuned by adjustment of oxidation time and temperature. This design provides a core-shell structure of TiO2/TiN nanowires integrated with silicon and sapphire substrates. The Rutile TiO2 nanowires show ferromagnetic behavior, while the as-grown TiN exhibits diamagnetic behavior. The SEM, TEM, and EBSD are used to characterize the microstructure and atomic alignments of TiO2 nanowires. The simple method of oxidation combined with tunable magnetic properties provides benefits to many smart applications where the magnetic field can be used as an external stimulation.}, journal={Acta Materialia}, publisher={Elsevier BV}, author={Moatti, A. and Sachan, R. and Kumar, D. and Narayan, J.}, year={2019}, month={Apr}, pages={112–120} }
 @article{moatti_sachan_cooper_narayan_2019, title={Electrical Transition in Isostructural VO2 Thin-Film Heterostructures}, volume={9}, ISSN={2045-2322}, url={http://dx.doi.org/10.1038/S41598-019-39529-Z}, DOI={10.1038/s41598-019-39529-z}, abstractNote={Abstract}, number={1}, journal={Scientific Reports}, publisher={Springer Science and Business Media LLC}, author={Moatti, Adele and Sachan, Ritesh and Cooper, Valentino R and Narayan, Jagdish}, year={2019}, month={Feb} }
 @article{sachan_hachtel_bhaumik_moatti_prater_idrobo_narayan_2019, title={Emergence of shallow energy levels in B-doped Q-carbon: A high-temperature superconductor}, volume={174}, url={https://doi.org/10.1016/j.actamat.2019.05.013}, DOI={10.1016/j.actamat.2019.05.013}, abstractNote={We report the spectroscopic demonstration of the shallow-level energy states in the recently discovered B-doped Q-carbon Bardeen-Cooper-Schrieffer (BCS) high-temperature superconductor. The Q-carbon is synthesized by ultrafast melting and quenching, allowing for high B-doping concentrations which increase the superconducting transition temperature (Tc) to 36 K (compared to 4 K for B-doped diamond). The increase in Tc is attributed to the increased density of energy states near the Fermi level in B-doped Q-carbon, which give rise to superconducting states via strong electron-phonon coupling below Tc. These shallow-level energy states, however, are challenging to map due to limited spatial and energy resolution. Here, we use ultrahigh energy resolution monochromated electron energy-loss spectroscopy (EELS), to detect and visualize the newly formed shallow-level energy states (vibrational modes) near the Fermi level (ranging 30–100 meV) of the B-doped Q-carbon. With this study, we establish the significance of high-resolution EELS in understanding the superconducting behavior of BCS superconducting C-based materials, which demonstrate a phenomenal enhancement in the presence of shallow-level energy states.}, journal={Acta Materialia}, publisher={Elsevier BV}, author={Sachan, Ritesh and Hachtel, Jordan A. and Bhaumik, Anagh and Moatti, Adele and Prater, John and Idrobo, Juan Carlos and Narayan, Jagdish}, year={2019}, month={Aug}, pages={153–159} }
 @article{gupta_moatti_bhaumik_sachan_narayan_2019, title={Room-temperature ferromagnetism in epitaxial titanium nitride thin films}, volume={166}, ISSN={1359-6454}, url={http://dx.doi.org/10.1016/J.ACTAMAT.2018.12.041}, DOI={10.1016/j.actamat.2018.12.041}, abstractNote={Localized charge injection by formation of vacancies provides an attractive platform for the development of multifunctional nanomaterials with direct implications in spintronics. However, further progress in spintronics critically depends on a deeper understanding of polaronic interactions between the localized charge states. This report is focused on TiN metallic system, which exhibits Pauli paramagnetism due to the absence of unpaired localized spin states. Here, nitrogen vacancies (VN) are used as a variable to tune the magnetic properties of epitaxial TiN thin films by thermal annealing in high-vacuum and N2 environment. Systematic introduction of VN generates robust magnetic ordering in vacuum-annealed TiN1-x films, with Curie temperature (TC) ∼700 K, and saturation magnetization (Ms) at absolute zero of 13.6 emu g−1. The signature spin-glass behavior below the irreversibility temperature (Tir ∼40 K) indicates the Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling interactions between the unpaired localized spin-states. Through spatially resolved electron energy-loss spectroscopy, we have determined the generation of unpaired localized spins at Ti+2 polarons with ∼12 ± 2 at.% VN in TiN1-x films. Such a large concentration of VN results in increased spin stiffness and high TC. These findings open a definitive pathway for tuning the magnetic nature of metallic materials for spintronic applications.}, journal={Acta Materialia}, publisher={Elsevier BV}, author={Gupta, Siddharth and Moatti, Adele and Bhaumik, Anagh and Sachan, Ritesh and Narayan, Jagdish}, year={2019}, month={Mar}, pages={221–230} }
 @article{moatti_sachan_prater_narayan_2018, title={An optimized sample preparation approach for atomic resolution in situ studies of thin films}, volume={81}, ISSN={1059-910X 1097-0029}, url={http://dx.doi.org/10.1002/JEMT.23130}, DOI={10.1002/jemt.23130}, abstractNote={Abstract}, number={11}, journal={Microscopy Research and Technique}, publisher={Wiley}, author={Moatti, Adele and Sachan, Ritesh and Prater, John and Narayan, Jagdish}, year={2018}, month={Oct}, pages={1250–1256} }
 @article{moatti_narayan_2018, title={High-quality TiN/AlN thin film heterostructures on c-sapphire}, volume={145}, ISSN={["1873-2453"]}, url={https://doi.org/10.1016/j.actamat.2017.11.044}, DOI={10.1016/j.actamat.2017.11.044}, abstractNote={We have developed TiN/AlN/c-sapphire epitaxial heterostructures and compared it with TiN/c-sapphire epitaxial heterostructures, needed for GaN-based LEDs and lasers. AlN is used as a buffer layer to provide a high misfit strain and facilitate the 2D growth on sapphire. The large misfit strain between sapphire and AlN makes this substrate a great candidate for GaN-based devices because it guarantees a full relaxation of AlN thin films through domain matching epitaxy paradigm. TiN can also act as an excellent contact and bottom electrode for Ⅲ-Ⅴ nitrides. Also, the introduction of TiN as a buffer layer decreases the critical thickness beyond which dislocations can grow in GaN thin films due to higher misfit strain compared to sapphire, which also improves the quality of potential GaN thin films. The selected-area-electron-diffraction patterns, scanning transmission electron microscopy, and transmission Kikuchi diffractions along with atomic arrangement simulations revealed that films are epitaxial with the following relationships: TiN<101>‖AlN[1¯21¯0]‖sapphire[011¯0] (in-plane), and TiN<111>‖AlN[0001]‖sapphire[0001] (out-of-plane). This is equivalent to a 30° rotation of Al basal plane in AlN with respect to that in sapphire. In TiN/c-sapphire epitaxial platforms, there is a 30° rotation: TiN<101>‖sapphire[011¯0] (in-plane), and TiN<111>‖sapphire[0001] (out-of-plane). It is shown that these heterostructures are fully relaxed in terms of misfit strains and only thermal strain stays as unrelaxed. The domain matching epitaxy paradigm is used to rationalize the epitaxial growth. The details of dislocations nucleation and glide in these heterostructures were studied and the results also discussed to elucidate the mechanism of strain relaxation.}, journal={ACTA MATERIALIA}, publisher={Elsevier BV}, author={Moatti, A. and Narayan, J.}, year={2018}, month={Feb}, pages={134–141} }
 @article{jaipan_nannuri_mucha_singh_xu_moatti_narayan_fialkova_kotoka_yarmolenko_et al._2018, title={Influence of Gold Catalyst on the Growth o Titanium Nitride Nanowires}, volume={7}, ISSN={["2169-4303"]}, DOI={10.1166/mat.2018.1571}, number={5}, journal={MATERIALS FOCUS}, author={Jaipan, Panupong and Nannuri, Chandra and Mucha, Nikhil Reddy and Singh, Mayur P. and Xu, Zhigang and Moatti, Adele and Narayan, Jay and Fialkova, Svitlana and Kotoka, Ruben and Yarmolenko, Sergey and et al.}, year={2018}, month={Oct}, pages={720–725} }
 @article{moatti_sachan_gupta_narayan_2018, title={Vacancy-Driven Robust Metallicity of Structurally Pinned Monoclinic Epitaxial VO2 Thin Films}, volume={11}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/ACSAMI.8B17879}, DOI={10.1021/acsami.8b17879}, abstractNote={Vanadium dioxide (VO2) is a strongly correlated material with 3d electrons, which exhibits temperature-driven insulator-to-metal transition with a concurrent change in the crystal symmetry. Interestingly, even modest changes in stoichiometry-induced orbital occupancy dramatically affect the electrical conductivity of the system. Here, we report a successful transformation of epitaxial monoclinic VO2 thin films from a conventionally insulating to permanently metallic behavior by manipulating the electron correlations. These ultrathin (∼10 nm) epitaxial VO2 films were grown on NiO(111)/Al2O3(0001) pseudomorphically, where the large misfit between NiO and Al2O3 were fully relaxed by domain-matching epitaxy. Complete conversion from an insulator to permanent metallic phase is achieved through injecting oxygen vacancies ( x ∼ 0.20 ± 0.02) into the VO2- x system via annealing under high vacuum (∼5 × 10-7 Torr) and increased temperature (450 °C). Systematic introduction of oxygen vacancies partially converts V4+ to V3+ and generates unpaired electron charges which result in the emergence of donor states near the Fermi level. Through the detailed study of the vibrational modes by Raman spectroscopy, hardening of the V-V vibrational modes and stabilization of V-V dimers are observed in vacuum-annealed VO2 films, providing conclusive evidence for stabilization of a monoclinic phase. This ultimately leads to convenient free-electron transport through the oxygen-deficient VO2- x thin films, resulting in metallic characteristics at room temperature. With these results, we propose a defect engineering pathway through the control of oxygen vacancies to tune electrical and optical properties in epitaxial monoclinic VO2.}, number={3}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Moatti, Adele and Sachan, Ritesh and Gupta, Siddharth and Narayan, Jagdish}, year={2018}, month={Dec}, pages={3547–3554} }
 @article{moatti_sachan_prater_narayan_2017, title={Control of Structural and Electrical Transitions of VO2 Thin Films}, volume={9}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.7b05620}, DOI={10.1021/acsami.7b05620}, abstractNote={Unstrained and defect-free VO2 single crystals undergo structural (from high-temperature tetragonal to low-temperature monoclinic phase) and electronic phase transitions simultaneously. In thin films, however, in the presence of unrelaxed strains and defects, structural (Peierls) and electronic (Mott) transitions are affected differently, and are separated. In this paper, we have studied the temperature dependence of structural and electrical transitions in epitaxially grown vanadium dioxide films on (0001) sapphire substrates. These results are discussed using a combined kinetics and thermodynamics approach, where the velocity of phase transformation is controlled largely by kinetics, and the formation of intermediate phases is governed by thermodynamic considerations. We have grown (020) VO2 on (0001) sapphire with two (001) and (100) in-plane orientations rotated by 122°. The (100)-oriented crystallites are fully relaxed by the paradigm of domain-matching epitaxy, whereas (001) crystallites are not relaxed and exhibit the formation of a few atomic layers of thin interfacial V2O3. We have studied the structural (Peierls) transition by temperature-dependent in situ X-ray diffraction measurements, and electronic (Mott) transition by electrical resistance measurements. A delay of 3 °C is found between the onset of structural (76 °C) and electrical (73 °C) transitions in the heating cycle. This temporal lag in the transition is attributed to the residual strain existing in the VO2 crystallites. With this study, we suggest that the control of structural and electrical transitions is possible by varying the transition activation barrier for atomic jumps through the strain engineering.}, number={28}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Moatti, Adele and Sachan, Ritesh and Prater, John and Narayan, Jay}, year={2017}, month={Jul}, pages={24298–24307} }
 @article{moatti_bayati_narayan_2016, title={Epitaxial growth of rutile TiO2 thin films by oxidation of TiN/Si{100} heterostructure}, volume={103}, ISSN={["1873-2453"]}, url={https://doi.org/10.1016/j.actamat.2015.10.022}, DOI={10.1016/j.actamat.2015.10.022}, abstractNote={We have integrated epitaxial TiO2 on a TiN/Si(100) platform through oxidation of TiN. The oxidation of TiN(100)/Si(100) results in the formation of an epitaxial rutile-TiO2 (r-TiO2) with a [110] out-of-plane orientation. We have studied in detail the r-TiO2 epitaxy and the epitaxial relationship is determined to be TiO2(11¯0)||TiN(100) and TiO2(110)||TiN(110). We rationalized this epitaxy using the domain matching epitaxy paradigm. Below the r-TiO2 epitaxial layer, we observed cuboids, which are mostly voids. We described the mechanism of oxidation where Ti out diffusion during oxidation leads to collapse of the nitrogen octahedron. This collapse makes neighboring Ti bonds weaker, promoting these Ti atoms to diffuse out next. Thus, cuboids filled with atomic nitrogen are formed, which then form N2 gas. The N2 pressure in these cuboids was estimated to be as high as 359 MPa, assuming all N2 is retained in the cuboids. This pressure can exceed the fracture stress of TiO2 and leads to rupture of thin TiO2 surface, which has been observed under certain conditions.}, journal={ACTA MATERIALIA}, publisher={Elsevier BV}, author={Moatti, A. and Bayati, R. and Narayan, J.}, year={2016}, month={Jan}, pages={502–511} }
 @article{moatti_bayati_singamaneni_narayan_2016, title={Epitaxial integration of TiO2 with Si(100) through a novel approach of oxidation of TiN/Si(100) epitaxial heterostructure}, volume={1}, ISSN={["2059-8521"]}, DOI={10.1557/adv.2016.463}, abstractNote={In this study, we provide a novel approach to the epitaxial integration of TiO_2 with Si(100) and investigate the defect mediated ferromagnetism in TiO_2 structure. Epitaxial TiO_2 thin films were grown on a TiN/Si(100) epitaxial heterostructure through oxidation of TiN where a single crystalline rutile-TiO_2 (r-TiO_2) with a [110] out-of-plane orientation was obtained. The epitaxial relationship is determined to be TiO_2(1 $\overline 1 $ 0)||TiN(100) and TiO_2(110)||TiN(110). We rationalized this epitaxy using the domain matching epitaxy paradigm. First TiN is grown epitaxially on Si(100). Subsequently, TiN/Si(100) samples are oxidized to create r-TiO_2/TiN/Si(100) epitaxial heterostructures. The details of the mechanism behind the oxidation of single crystalline TiN to TiO_2 was investigated using atomic scale high resolution electron microscopy techniques. Defects introduced to the heterostructure during oxidation caused ferromagnetism in TiO_2 thin film which is reversible and can be tuned by controlling oxygen partial pressure. The source of magnetization is correlated with the presence of oxygen vacancy leading to introduction of two localized states; hybrid and polaron among neighboring Ti atoms, and titanium vacancy providing four holes to form molecular oxygen. We present structure property correlations and its impact on the next generation solid state devices.}, number={37}, journal={MRS ADVANCES}, author={Moatti, A. and Bayati, R. and Singamaneni, S. and Narayan, J.}, year={2016}, pages={2629–2634} }
 @article{moatti_bayati_singamaneni_narayan_2016, title={Thin film bi-epitaxy and transition characteristics of TiO2/TiN buffered VO2 on Si(100) substrates}, volume={1}, ISSN={["2059-8521"]}, DOI={10.1557/adv.2016.544}, abstractNote={Bi-epitaxial VO_2 thin films with [011] out-of-plane orientation were integrated with Si(100) substrates through TiO_2/TiN buffer layers. At the first step, TiN is grown epitaxially on Si(100), where a cube-on-cube epitaxy is achieved. Then, TiN was oxidized in-situ ending up having epitaxial r-TiO_2. Finally, VO_2 was deposited on top of TiO_2. The alignment across the interfaces was stablished as VO_2(011)║TiO_2(110)║TiN(100)║Si(100) and VO_2(110) /VO_2(010)║TiO_2(011)║TiN(112)║Si(112). The inter-planar spacing of VO_2(010) and TiO_2(011) equal to 2.26 and 2.50 Å, respectively. This results in a 9.78% tensile misfit strain in VO_2(010) lattice which relaxes through 9/10 alteration domains with a frequency factor of 0.5, according to the domain matching epitaxy paradigm. Also, the inter-planar spacing of VO_2(011) and TiO_2(011) equals to 3.19 and 2.50 Å, respectively. This results in a 27.6% compressive misfit strain in VO_2(011) lattice which relaxes through 3/4 alteration domains with a frequency factor of 0.57. We studied semiconductor to metal transition characteristics of VO_2/TiO_2/TiN/Si heterostructures and established a correlation between intrinsic defects and magnetic properties.}, number={37}, journal={MRS ADVANCES}, author={Moatti, Adele and Bayati, Reza and Singamaneni, Srinivasa Rao and Narayan, Jagdish}, year={2016}, pages={2635–2640} }