@article{jin_aggarwal_wei_nori_kumar_ponarin_smirnov_narayan_narayan_2011, title={Intrinsic Room-Temperature Ferromagnetic Properties of Ni-Doped ZnO Thin Films}, volume={42}, ISSN={1073-5623 1543-1940}, url={http://dx.doi.org/10.1007/S11661-010-0479-9}, DOI={10.1007/s11661-010-0479-9}, number={11}, journal={Metallurgical and Materials Transactions A}, publisher={Springer Science and Business Media LLC}, author={Jin, C. and Aggarwal, R. and Wei, W. and Nori, S. and Kumar, D. and Ponarin, D. and Smirnov, A. I. and Narayan, J. and Narayan, R. J.}, year={2011}, month={Nov}, pages={3250–3254} } @article{wei_nori_jin_narayan_narayan_ponarin_smirnov_2010, title={Mott transition in Ga-doped MgxZn1-xO: A direct observation}, volume={171}, ISSN={["1873-4944"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77953133966&partnerID=MN8TOARS}, DOI={10.1016/j.mseb.2010.03.078}, abstractNote={This paper reports the direct evidence for Mott transition in Ga-doped MgxZn1−xO thin films. Highly transparent Ga-doped MgxZn1−xO thin films were grown on c-plane sapphire substrates using pulsed laser deposition. 0.1 at.%, 0.5 at.% and 1 at.% Ga-doped Mg0.1Zn0.9O films were selected for resistivity measurements in the temperature range from 250 K to 40 mK. The 0.1 at.% Ga-doped Mg0.1Zn0.9O thin film showed typical insulator-like behavior and the 1 at.% Ga-doped Mg0.1Zn0.9O thin film showed typical metal-like behavior. The 0.5 at.% Ga-doped Mg0.1Zn0.9O film showed increasing resistivity with decreasing temperature; resistivity was saturated with a value of 1.15 × 10−2 Ω cm at 40 mK, which is characteristic of the metal–insulator transition region. Temperature-dependent conductivity σ(T) in the low temperature range revealed that the electron-electron scattering is the dominant dephasing mechanism. The inelastic scattering time is found to vary as T−3/2.}, number={1-3}, journal={MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS}, publisher={Elsevier BV}, author={Wei, Wei and Nori, Sudhakar and Jin, Chunming and Narayan, Jagdish and Narayan, Roger J. and Ponarin, Dmtri and Smirnov, Alex}, year={2010}, month={Jul}, pages={90–92} } @article{gittard_perfect_monteiro-riviere_wei_jin_narayan_2009, title={Assessing the antimicrobial activity of zinc oxide thin films using disk diffusion and biofilm reactor}, volume={255}, ISSN={["1873-5584"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000263893800027&KeyUID=WOS:000263893800027}, DOI={10.1016/j.apsusc.2009.01.009}, abstractNote={The electronic and chemical properties of semiconductor materials may be useful in preventing growth of microorganisms. In this article, in vitro methods for assessing microbial growth on semiconductor materials will be presented. The structural and biological properties of silicon wafers coated with zinc oxide thin films were evaluated using atomic force microscopy, X-ray photoelectron spectroscopy, and MTT viability assay. The antimicrobial properties of zinc oxide thin films were established using disk diffusion and CDC Biofilm Reactor studies. Our results suggest that zinc oxide and other semiconductor materials may play a leading role in providing antimicrobial functionality to the next-generation medical devices.}, number={11}, journal={APPLIED SURFACE SCIENCE}, author={Gittard, Shaun D. and Perfect, John R. and Monteiro-Riviere, Nancy A. and Wei, Wei and Jin, Chunming and Narayan, Roger J.}, year={2009}, month={Mar}, pages={5806–5811} } @article{wei_jin_narayan_narayan_2009, title={Optical and electrical properties of bandgap engineered gallium-doped MgxZn1-xO films}, volume={149}, ISSN={["1879-2766"]}, DOI={10.1016/j.ssc.2009.06.021}, abstractNote={In this study, the optical and electrical properties of heavily gallium-doped MgxZn1−xO films were investigated. Films were epitaxially grown on c-plane sapphire substrates using pulsed laser deposition. Film transparency was shown to be greater than 90% in the visible spectrum. Absorption was shown to be extended to lower wavelengths in films with higher magnesium concentration values. Although transparency in the ultraviolet wavelength range was improved, conductivity was decreased. In MgxZn1−xO films with 0.5 at.% gallium, resistivity was increased from 1.9×10−3Ωcm to 3.62×10−2Ωcm as the magnesium concentration was increased from five atomic percent to fifteen atomic percent. These efforts will facilitate the development of zinc oxide-based ultraviolet–blue light emitting diodes, ultraviolet–blue light laser diodes, and other optoelectronic devices.}, number={39-40}, journal={SOLID STATE COMMUNICATIONS}, author={Wei, Wei and Jin, Chunming and Narayan, Jagdish and Narayan, Roger J.}, year={2009}, month={Oct}, pages={1670–1673} } @article{jin_wei_zhou_yang_narayan_2008, title={Epitaxial growth and Ohmic contacts in MgxZn1-xO/TiN/Si(111) heterostructures}, volume={93}, ISSN={["1077-3118"]}, DOI={10.1063/1.3054347}, abstractNote={In this work, the electronic properties of Mg0.1Zn0.9O∕TiN∕Si(111) heterostructures processed using pulsed laser deposition were examined. X-ray diffraction and transmission electron microscopy studies demonstrated epitaxial growth of the titanium nitride buffer layer and the Mg0.1Zn0.9O thin film. Transmission electron microscopy demonstrated a thin (∼5nm) spinel layer along the magnesium zinc oxide/titanium nitride interface. Current-voltage measurements revealed Ohmic contact behavior through the magnesium zinc oxide/titanium nitride interface. These results suggest that the titanium nitride buffer layer in the MgxZn1−xO∕TiN∕Si(111) heterostructure provides a buffer layer for integrating magnesium zinc oxide thin films with silicon substrates, which both enable epitaxial growth and serve as an Ohmic electrode for the magnesium zinc oxide thin film.}, number={25}, journal={APPLIED PHYSICS LETTERS}, author={Jin, Chunming and Wei, Wei and Zhou, Honghui and Yang, Tsung-Han and Narayan, Roger J.}, year={2008}, month={Dec} } @article{narayan_aggarwal_wei_jin_monteiro-riviere_crombez_shen_2008, title={Mechanical and biological properties of nanoporous carbon membranes}, volume={3}, ISSN={["1748-605X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000258916500020&KeyUID=WOS:000258916500020}, DOI={10.1088/1748-6041/3/3/034107}, abstractNote={Implantable blood glucose sensors have inadequate membrane–tissue interfaces for long term use. Biofouling and inflammation processes restrict biosensor membrane stability. An ideal biosensor membrane material must prevent protein adsorption and exhibit cell compatibility. In addition, a membrane must exhibit high porosity and low thickness in order to allow the biosensor to respond to analyte fluctuations. In this study, the structural, mechanical and biological properties of nanoporous alumina membranes coated with diamond-like carbon thin films were examined using scanning probe microscopy, nanoindentation and MTT viability assay. We anticipate that this novel membrane material could find use in immunoisolation devices, kidney dialysis membranes and other medical devices encountering biocompatibility issues that limit in vivo function.}, number={3}, journal={BIOMEDICAL MATERIALS}, author={Narayan, Roger J. and Aggarwal, Ravi and Wei, Wei and Jin, Chunming and Monteiro-Riviere, Nancy A. and Crombez, Rene and Shen, Weidian}, year={2008}, month={Sep} } @article{jin_nori_wei_aggarwal_kumar_narayan_2008, title={Pulsed Laser Deposition of Nanoporous Cobalt Thin Films}, volume={8}, ISSN={["1533-4899"]}, DOI={10.1166/jnn.2008.483}, abstractNote={Nanoporous cobalt thin films were deposited on anodized aluminum oxide (AAO) membranes at room temperature using pulsed laser deposition. Scanning electron microscopy demonstrated that the nanoporous cobalt thin films retained the monodisperse pore size and high porosity of the anodized aluminum oxide substrates. Temperature- and field-dependent magnetic data obtained between 10 K and 350 K showed large hysteresis behavior in these materials. The increase of coercivity values was larger for nanoporous cobalt thin films than for multilayered cobalt/alumina thin films. The average diameter of the cobalt nanograins in the nanoporous cobalt thin films was estimated to be ∼5 nm for blocking temperatures near room temperature. These results suggest that pulsed laser deposition may be used to fabricate nanoporous magnetic materials with unusual properties for biosensing, drug delivery, data storage, and other technological applications.}, number={11}, journal={JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY}, author={Jin, Chunming and Nori, Sudhakar and Wei, Wei and Aggarwal, Ravi and Kumar, Dhananjay and Narayan, Roger J.}, year={2008}, month={Nov}, pages={6043–6047} } @article{narayan_pant_wei_narayan_budai_2007, title={Nanostructured GaN nucleation layer for light-emitting diodes}, volume={7}, ISSN={["1533-4899"]}, DOI={10.1166/jnn.2007.670}, abstractNote={This paper addresses the formation of nanostructured gallium nitride nucleation (NL) or initial layer (IL), which is necessary to obtain a smooth surface morphology and reduce defects in h-GaN layers for light-emitting diodes and lasers. From detailed X-ray and HR-TEM studies, researchers determined that this layer consists of nanostructured grains with average grain size of 25 nm, which are separated by small-angle grain boundaries (with misorientation approximately 1 degrees), known as subgrain boundaries. Thus NL is considered to be single-crystal layer with mosaicity of about 1 degrees. These nc grains are mostly faulted cubic GaN (c-GaN) and a small fraction of unfaulted c-GaN. This unfaulted Zinc-blende c-GaN, which is considered a nonequilibrium phase, often appears as embedded or occluded within the faulted c-GaN. The NL layer contained in-plane tensile strain, presumably arising from defects due to island coalescence during Volmer-Weber growth. The 10L X-ray scans showed c-GaN fraction to be over 63% and the rest h-GaN. The NL layer grows epitaxially with the (0001) sapphire substrate by domain matching epitaxy, and this epitaxial relationship is remarkably maintained when c-GaN converts into h-GaN during high-temperature growth.}, number={8}, journal={JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY}, author={Narayan, J. and Pant, P. and Wei, W. and Narayan, R. J. and Budai, J. D.}, year={2007}, month={Aug}, pages={2719–2725} } @article{narayan_wei_jin_andara_agarwal_gerhardt_shih_shih_lin_su_et al._2006, title={Microstructural and biological properties of nanocrystalline diamond coatings}, volume={15}, ISSN={["1879-0062"]}, DOI={10.1016/j.diamond.2006.08.024}, abstractNote={In this study, the microstructural, mechanical, adhesion, and hemocompatibility properties of nanocrystalline diamond coatings were examined. Microwave plasma chemical vapor deposition (MPCVD) was used to deposit nanocrystalline diamond coatings on silicon (100) substrates. The coating surface consisted of faceted nodules, which exhibited a relatively wide size distribution and an average size of 60 nm. High-resolution transmission electron microscopy demonstrated that these crystals were made up of 2–4 nm rectangular crystallites. Raman spectroscopy and electron diffraction revealed that the coating contained both crystalline and amorphous phases. The microscratch adhesion study demonstrated good adhesion between the coating and the underlying substrate. Scanning electron microscopy and energy dispersive X-ray analysis revealed no crystal, fibrin, protein, or platelet aggregation on the surface of the platelet rich plasma-exposed nanocrystalline diamond coating. This study suggests that nanocrystalline diamond is a promising coating for use in cardiovascular medical devices.}, number={11-12}, journal={DIAMOND AND RELATED MATERIALS}, author={Narayan, R. J. and Wei, W. and Jin, C. and Andara, M. and Agarwal, A. and Gerhardt, R. A. and Shih, Chun-Che and Shih, Chun-Ming and Lin, Shing-Jong and Su, Yea-Yang and et al.}, year={2006}, pages={1935–1940} } @article{jin_zhou_wei_narayan_2006, title={Three-dimensional self-organization of crystalline gold nanoparticles in amorphous alumina}, volume={89}, DOI={10.1063/1.2422910}, abstractNote={Multilayered heterostructures containing gold nanoparticles embedded in amorphous alumina matrices were deposited on silicon (001) substrates using pulsed laser deposition. The three-dimensional ordering of gold nanoparticles within these multilayered heterostructures was investigated using cross-sectional transmission electron microscopy and image Fourier transformation. Self-organization of gold nanoparticles along the vertical direction was observed in films grown at 20 and at 320°C. Self-organization occurred by means of two different growth modes; both vertically correlated growth (top-on-top) and anticorrelated growth (top-on-middle) mechanisms were observed. The results of these studies suggest that the driving force for vertical ordering in this material is related to the long-range elastic interactions among the nanoparticles within the growing films.}, number={26}, journal={Applied Physics Letters}, author={Jin, C. M. and Zhou, H. H. and Wei, W. and Narayan, R.}, year={2006} } @misc{wei_sethuraman_jin_monteiro-riviere_narayan, title={Biological properties of carbon nanotubes}, volume={7}, number={4-5}, journal={Journal of Nanoscience and Nanotechnology}, author={Wei, W. and Sethuraman, A. and Jin, C. and Monteiro-Riviere, N. A. and Narayan, R. J.}, pages={1284–1297} }