@article{singamaneni_prater_wu_narayan_2016, title={Ferromagnetic oxide heterostructures on silicon}, volume={6}, ISSN={["2159-6867"]}, DOI={10.1557/mrc.2016.22}, abstractNote={Heterostructures consisting of two ferromagnetic oxides La_0.7Ca_0.3MnO_3 (LCMO) and SrRuO_3 (SRO) were epitaxially grown by pulsed laser deposition onto a silicon (Si) substrate buffered by SrTiO_3 (STO)/MgO/TiN. The x-ray scans and electron-diffraction patterns reveal the epitaxial nature of all five layers. From transmission electron microscopy, the thicknesses of the LCMO and SRO layers were estimated to be -100 and -200 nm, respectively. The magnetic properties of individual SRO and LCMO layers are in good agreement with the previous studies reported for those individual layers deposited on lattice-matched substrates, such as STO. The LCMO/SRO heterostructures showed enhanced switching field (from 6008 to 7600 Oe), which may originate from the bulk part of the heterostructure. The ability to grow these multifunctional structures on Si provides a route for wafer scale integration with Si, in contrast to oxide substrates that are not suitable for CMOS integration for microelectronics and spintronics applications.}, number={3}, journal={MRS COMMUNICATIONS}, author={Singamaneni, Srinivasa Rao and Prater, J. T. and Wu, Fan and Narayan, J.}, year={2016}, month={Sep}, pages={234–240} }
 @article{molaei_bayati_wu_narayan_2014, title={A microstructural approach toward the effect of thickness on semiconductor-to-metal transition characteristics of VO2 epilayers}, volume={115}, number={16}, journal={Journal of Applied Physics}, author={Molaei, R. and Bayati, R. and Wu, F. and Narayan, J.}, year={2014} }
 @article{gbordzoe_kotoka_craven_kumar_wu_narayan_2014, title={Effect of substrate temperature on the microstructural properties of titanium nitride nanowires grown by pulsed laser deposition}, volume={116}, number={6}, journal={Journal of Applied Physics}, author={Gbordzoe, S. and Kotoka, R. and Craven, E. and Kumar, D. and Wu, F. and Narayan, J.}, year={2014} }
 @misc{lee_punugupati_wu_jin_narayan_schwartz_2014, title={Evidence for topological surface states in epitaxial Bi2Se3 thin film grown by pulsed laser deposition through magneto-transport measurements}, volume={18}, ISSN={["1879-0348"]}, DOI={10.1016/j.cossms.2014.07.001}, abstractNote={We report epitaxial growth via domain matching epitaxy of Bi2Se3 thin films on Al2O3 (0 0 0 1) substrates with over 13% lattice misfit and critical thickness less than one monolayer. X-ray and electron diffraction patterns confirm that the layers are epitaxial with (0 0 0 1) Bi2Se3 || (0 0 0 1) Al2O3 and [21¯1¯0] Bi2Se3 || [21¯1¯0] Al2O3 (or) [21¯1¯0] Bi2Se3 || [112¯0] Al2O3 without the presence of an interfacial pseudomorphic layer. X-ray photoemission spectroscopy reveals that the films are Se-deficient, in agreement with electrical transport data showing n-type carriers and metallic behavior. Magneto-resistance (MR) measurements show a cusp feature corresponding to weak antilocalization and linear-MR shows a non-saturating trend up to 9 T. These results suggest topological surface states in PLD-grown Bi2Se3 films.}, number={5}, journal={CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE}, author={Lee, Y. F. and Punugupati, S. and Wu, F. and Jin, Z. and Narayan, J. and Schwartz, J.}, year={2014}, month={Oct}, pages={279–285} }
 @misc{rao_prater_wu_nori_kumar_narayan_2014, title={Integration of epitaxial permalloy on Si (100) through domain matching epitaxy paradigm}, volume={18}, ISSN={["1879-0348"]}, DOI={10.1016/j.cossms.2013.07.004}, abstractNote={Abstract This paper addresses epitaxial integration of magnetic materials with Si (1 0 0) based solid state devices. Epitaxial Ni82.5Fe17.5 (permalloy, Py) thin films have been synthesized by pulsed laser deposition (PLD) on Si (1 0 0) using MgO/TiN as a template buffer. This epitaxial growth of these large lattice misfit systems was achieved through domain matching epitaxy (DME). The in-plane XRD pattern and selective area electron diffraction (SAED) results clearly indicate cube-on-cube epitaxial alignment. The bright field TEM image of Py/MgO/TiN/Si (1 0 0) heterostructure infers a Py layer thickness of ∼30 nm, with a well aligned island (150–200 nm) structure that is consistent with Volmer–Weber type growth. Magnetization data collected at 4 K and 300 K indicates that the easy axis of the magnetization lies in the plane of the Py. In addition, we have observed an intrinsic positive exchange bias (PEB) field of ∼104 Oe, where the magnetic hysteresis loop is shifted toward the positive field axis under zero field cooling conditions.}, number={1}, journal={CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE}, author={Rao, S. S. and Prater, J. T. and Wu, Fan and Nori, Sudhakar and Kumar, D. and Narayan, J.}, year={2014}, month={Feb}, pages={1–5} }
 @article{singamaneni_fan_prater_narayan_2014, title={Magnetic properties of BaTiO3/La0.7Sr0.3MnO3 thin films integrated on Si(100)}, volume={116}, number={22}, journal={Journal of Applied Physics}, author={Singamaneni, S. R. and Fan, W. and Prater, J. T. and Narayan, J.}, year={2014} }
 @article{lee_wu_narayan_schwartz_2014, title={Oxygen vacancy enhanced room-temperature ferromagnetism in Sr3SnO/c-YSZ/Si (001) heterostructures}, volume={4}, ISSN={["2159-6867"]}, DOI={10.1557/mrc.2014.4}, abstractNote={The magnetic properties of Sr_3SnO (SSO) epitaxial thin films prepared under various post-growth annealing treatments are reported. The SSO films are grown on cubic yttria-stabilized zirconia Si (001) platform by pulsed laser deposition. Post-growth vacuum annealing is found to enhance the room-temperature ferromagnetism (RTFM), whereas oxygen annealing reduces it. The results are explained through the oxygen vacancy constituted bound magnetic polarons (BMP) model. An empirical relationship between the extracted BMP concentration and the oxygen vacancy concentration is shown using X-ray photoelectron spectroscopy data. The results indicate a promising way to tune RTFM by manipulating oxygen vacancies and related defects.}, number={1}, journal={MRS COMMUNICATIONS}, author={Lee, Y. F. and Wu, F. and Narayan, J. and Schwartz, J.}, year={2014}, month={Apr}, pages={7–13} }
 @article{rao_prater_wu_nori_kumar_yue_liou_narayan_2014, title={Positive exchange bias in epitaxial permalloy/MgO integrated with Si (100)}, volume={18}, ISSN={1359-0286}, url={http://dx.doi.org/10.1016/J.COSSMS.2014.02.001}, DOI={10.1016/j.cossms.2014.02.001}, abstractNote={In magnetic random access memory (MRAM) devices, soft magnetic thin film elements such as permalloy (Py) are used as unit cells of information. The epitaxial integration of these elements with the technologically important substrate Si (1 0 0) and a thorough understanding of their magnetic properties are critical for CMOS-based magnetic devices. We report on the epitaxial growth of Ni82.5Fe17.5 (permalloy, Py) on Si (1 0 0) using a TiN/MgO buffer layer. Initial stages of growth are characterized by the formation of discrete islands that gradually merge into a continuous film as deposition times are extended. Interestingly, we find that the magnetic features of Py films in early stages of island coalescence are distinctly different from the films formed initially (discrete islands) and after extended deposition times (narrow distribution of equiaxed granular films). Isothermal in-plane and out-of-plane magnetic measurements performed on these transitional films show highly anisotropic magnetic behavior with an easy magnetization axis lying in the plane of the film. Importantly, when this sample is zero-field cooled, a positive exchange bias and vertical loop shift are observed, unusual for a soft ferromagnet like Py. Repeated field cycling and hysteresis loops up to the fields of 7T produced reproducible hysteresis loops indicating the existence of strongly pinned spin configurations. Classical interface related exchange bias models cannot explain the observed magnetic features of the transitional Py films. We believe that the anomalous magnetic behavior of such Py films may be explained by considering the highly irregular morphology that develops at intermediate growth times that are possibly also undergoing a transition from Bloch to Neel domain wall structures as a function of Py island size. This study broadens the current understanding of magnetic properties of Py thin layers for technological applications in magneto-electronic devices, integrated with Si (1 0 0).}, number={3}, journal={Current Opinion in Solid State and Materials Science}, publisher={Elsevier BV}, author={Rao, S.S. and Prater, J.T. and Wu, Fan and Nori, S. and Kumar, D. and Yue, L. and Liou, S.-H. and Narayan, J.}, year={2014}, month={Jun}, pages={140–146} }
 @misc{wu_rao_prater_zhu_narayan_2014, title={Tuning exchange bias in epitaxial Ni/MgO/TiN heterostructures integrated on Si(100)}, volume={18}, ISSN={["1879-0348"]}, DOI={10.1016/j.cossms.2014.09.002}, abstractNote={Epitaxial Ni thin films are integrated with tunneling barrier MgO on Si(1 0 0) substrate. During pulsed laser deposition, early island-like structure transformed into uniform thin film with increasing number of laser pulses. This led to transitions in exchange bias from positive to negative and back to positive, which is ascribed to morphology associated residual strain. The Ni island structure has a coercive field as high as 3 times of that of the continuous film. The current work holds a tremendous promise in the realization of magnetic devices integrated with the Si-platform.}, number={5}, journal={CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE}, author={Wu, F. and Rao, S. S. and Prater, J. T. and Zhu, Y. T. and Narayan, J.}, year={2014}, month={Oct}, pages={263–268} }
 @article{wu_narayan_2013, title={Controlled Epitaxial Growth of Body-Centered Cubic and Face-Centered Cubic Cu on MgO for Integration on Si}, volume={13}, ISSN={["1528-7505"]}, DOI={10.1021/cg4011983}, abstractNote={The Cu/MgO interface plays a crucial role in applications. Face-centered-cubic (fcc) Cu has been reported to grow on MgO substrate (rock salt structure). However, no body-centered-cubic/tetragonal (bcc(t)) Cu has been stabilized on MgO. The special atomic structure of the bcc(t)/rock salt interface contributes to superior thermal, mechanical, and electrical properties. We report, for the first time, the epitaxial growth of bcc(t) and fcc Cu on Si(100) and Si(111) substrates using MgO(100)/TiN(100) and MgO(111)/TiN(111) buffer layers by pulsed laser deposition. We find that the deposition temperature determines the structure of Cu. At high temperature, only fcc Cu grows on both MgO/TiN(100) and MgO/ TiN(111) templates. At room temperature, an epitaxial layer of bcc(t) Cu grows pseudomorphically on a MgO(100) template up to the critical thickness, while on a MgO/TiN(111) template, the majority of Cu is fcc, and bcc(t) Cu exists occasionally in a three-dimensional island shape. The growth of these heterostructures involves epitaxy across the misfit scale by matching MgO{200} planes with bcc(t) Cu{110} planes. The integration of Cu/MgO on the technologically important Si substrate holds tremendous promise, because the novel bcc(t) Cu/MgO structure can be integrated with present-day microelectronic or nanoelectronic devices.}, number={11}, journal={CRYSTAL GROWTH & DESIGN}, author={Wu, F. and Narayan, J.}, year={2013}, month={Nov}, pages={5018–5024} }
 @article{bayati_molaei_wu_budai_liu_narayan_narayan_2013, title={Correlation between structure and semiconductor-to-metal transition characteristics of VO2/TiO2/sapphire thin film heterostructures}, volume={61}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2013.09.019}, abstractNote={This study focuses on the role of strain and thin film epitaxy on the semiconductor-to-metal transition (SMT) characteristics of single crystalline VO2 thin films. The VO2/TiO2 heterostructures of controlled orientations were epitaxially grown on m-cut, r-cut and c-cut sapphire substrates. Detailed structural investigations were performed using high-resolution X-ray diffraction (2θ–θ and φ scans) and high-resolution transmission electron microscopy techniques to correlate SMT properties with microstructural characteristics. Monoclinic (M1) VO2 thin films with (1 0 0), (0 0 1) and (2¯01) out-of-plane orientations were grown on TiO2(1 0 1)/r-sapphire, TiO2(1 0 0)/c-sapphire and TiO2(0 0 1)/m-sapphire platforms, respectively. The in-plane alignments across the interfaces were established to be [0 1 0](1 0 0)VO2||[0 1 0](1 0 1)TiO2, [1 0 0](0 0 1)VO2||[0 0 1](1 0 0)TiO2 and [010](2¯01)VO2‖[010](001)TiO2 for r-sapphire, c-sapphire and m-sapphire substrates, respectively. We were able to tune the SMT temperature of VO2 epilayers from ∼313 K to 354 K (bulk Tc ≈ 340 K). The SMT characteristics were interpreted based upon the residual strain in the VO2 lattice, particularly along the c-axis of tetragonal VO2. This research introduces the VO2-based single crystalline heterostructures as a potential candidate for a wide range of applications where different transition temperatures are required.}, number={20}, journal={ACTA MATERIALIA}, author={Bayati, M. R. and Molaei, R. and Wu, F. and Budai, J. D. and Liu, Y. and Narayan, R. J. and Narayan, J.}, year={2013}, month={Dec}, pages={7805–7815} }
 @article{gupta_singh_wu_narayan_mcmillen_alapatt_poole_hwu_sulejmanovic_young_et al._2013, title={Deposition and characterization of nanostructured Cu2O thin-film for potential photovoltaic applications}, volume={28}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2013.150}, abstractNote={Abstract}, number={13}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Gupta, Nishant and Singh, Rajendra and Wu, Fan and Narayan, Jagdish and McMillen, Colin and Alapatt, Githin F. and Poole, Kelvin F. and Hwu, Shiou-Jyh and Sulejmanovic, Dino and Young, Matthew and et al.}, year={2013}, month={Jul}, pages={1740–1746} }
 @article{lee_wu_kumar_hunte_schwartz_narayan_2013, title={Epitaxial integration of dilute magnetic semiconductor Sr3SnO with Si (001)}, volume={103}, number={11}, journal={Applied Physics Letters}, author={Lee, Y. F. and Wu, F. and Kumar, R. and Hunte, F. and Schwartz, J. and Narayan, J.}, year={2013} }
 @article{wu_zhu_narayan_2013, title={Grain size effect on twin density in as-deposited nanocrystalline Cu film}, volume={93}, number={35}, journal={Philosophical Magazine}, author={Wu, F. and Zhu, Y. T. and Narayan, J.}, year={2013}, pages={4355–4363} }
 @article{rao_prater_wu_shelton_maria_narayan_2013, title={Interface Magnetism in Epitaxial BiFeO3-La0.7Sr0.3MnO3 Heterostructures Integrated on Si(100)}, volume={13}, ISSN={["1530-6992"]}, DOI={10.1021/nl4023435}, abstractNote={We report on the heteroepitaxial growth of ferroelectric (FE)-antiferromagnetic (AFM) BiFeO3 (BFO) on ferromagnetic La0.7Sr0.3MnO3 (LSMO), integrated on Si(100) using pulsed laser deposition via the domain matching epitaxy paradigm. The BFO/LSMO films were epitaxially grown on Si(100) by introducing epitaxial layers of SrTiO3/MgO/TiN. X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photo absorption spectroscopy, and atomic force microscopy were employed to fully characterize the samples. Furthermore, we have investigated the magnetic behavior of this five layer heterostructure, in which a d(5) system (Fe(3+)) manifested in FE-AFM BFO is epitaxially conjoined at the interface to a multivalent transition metal ion such as Mn(3+)/Mn(4+) in LSMO. The temperature- and magnetic field-dependent magnetization measurements reveal an unexpected enhancement in magnetic moment and improved magnetic hysteresis squareness originating from the BFO/LSMO interface. We observe a stronger temperature dependence of HEB when the polarity of field cooling is negative as compared to positive field cooling. We believe such an enhancement in magnetic moment and magnetic coupling is likely directly related to an electronic orbital reconstruction at the interface and complex interplay between orbital and spin degrees of freedom, similar to what has previously been reported in the literature. Future work will involve the linearly polarized X-ray absorption measurements to prove this hypothesis. This work represents a starting step toward the realization of magneto-electronic devices integrated with Si(100).}, number={12}, journal={NANO LETTERS}, author={Rao, S. S. and Prater, J. T. and Wu, Fan and Shelton, C. T. and Maria, J. -P. and Narayan, J.}, year={2013}, month={Dec}, pages={5814–5821} }
 @article{wu_wen_lavernia_narayan_zhu_2013, title={Twin intersection mechanisms in nanocrystalline fcc metals}, volume={585}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2013.07.063}, abstractNote={Deformation twins have been reported to produce high strength and ductility. Intersections of deformation twins may affect the microstructural evolution during plastic deformation and consequently influence mechanical properties. However, the mechanisms governing twin-intersection behavior remain poorly understood. In this study, we investigated twin intersection mechanisms by observing twin transmission across the boundary of another twin using high-resolution transmission electron microscopy. Based on the experimental observations, mechanisms were proposed for twin–twin intersections and associated dislocation reactions in nanocrystalline fcc materials.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Wu, F. and Wen, H. M. and Lavernia, E. J. and Narayan, J. and Zhu, Y. T.}, year={2013}, month={Nov}, pages={292–296} }