@article{sharma_kalyanaraman_narayan_oktyabrsky_narayan_2001, title={Carbon nanotube composites synthesized by ion-assisted pulsed laser deposition}, volume={79}, ISSN={["0921-5107"]}, DOI={10.1016/s0921-5107(00)00558-4}, abstractNote={We have synthesized thin CNx films on Si (100) substrate at high temperatures (600 and 700°C) by nitrogen ion-assisted pulsed laser deposition (PLD). The bonding characteristics and microstructure determinations have been accomplished using X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM), respectively. The radial distribution function (RDF) analysis of the electron diffraction patterns was performed to determine the short range atomic order in these films. The results reveal the presence of carbon predominantly in the trigonally-coordinated state with small fractions of nitrogen (upto 20 at.%) bonded to carbon. The electron diffraction and the high resolution images in cross-section view reveal that there is a textured growth of nanotube or graphite-like ribbons. The plan-view specimens show high resolution images with bended layers similar to that of onion or nanotube like features. The kinetics of the ions assisting the growth is assumed to be important to grow the basal planes (00l) of graphite perpendicular to the substrate. The large anisotropic surface energies in two perpendicular directions in graphite suggest that ions can create nonequilibrium conditions to alter the growth mode of graphitic planes. The importance of ion-assisted PLD to grow novel nanotube or fullerenelike structure in the form of thin film composites for electron field emission devices is emphasized.}, number={2}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Sharma, AK and Kalyanaraman, R and Narayan, RJ and Oktyabrsky, S and Narayan, J}, year={2001}, month={Jan}, pages={123–127} }
 @article{oktyabrsky_kalyanaraman_jagannadham_narayan_1999, title={Dislocation structure of low-angle grain boundaries in YBa2Cu3O7-delta/MgO films}, volume={14}, ISSN={["0884-2914"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032678410&partnerID=MN8TOARS}, DOI={10.1557/JMR.1999.0369}, abstractNote={Grain boundaries in laser-deposited YBa2Cu3O7−δ(YBCO)/MgO thin films have been investigated by high-resolution transmission electron microscopy. The films exhibit perfect texturing with YBCO(001)/MgO(001) giving rise to low-angle [001] tilt grain boundaries resulting from the grains with thecaxis normal to the substrate surface and with misorientation in thea-bplane. The atomic structure of the grain boundaries was analyzed by using a dislocation model. Low-angle grain boundaries have been found to be aligned along (100) and (110) interface planes. For the (110) boundary plane, the low-energy dislocation configuration was found to consist of an array of alternating [100] and [010] dislocations. We have calculated the energy of various configurations and shown that the energy of the (110) boundary with dissociated dislocations is comparable to that of the (100) boundary, which explains the coexistence of (100) and (110) interface facets along the boundary. We have also modeled critical current transport through grain boundaries with various structures and found that the low-energy (110) grain boundary with dissociated dislocation array is expected to transport a lower superconducting current (by 25% for 6° misorientation) than (100) boundaries.}, number={7}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Oktyabrsky, S and Kalyanaraman, R and Jagannadham, K and Narayan, J}, year={1999}, month={Jul}, pages={2764–2772} }
 @article{kalyanaraman_oktyabrsky_narayan_1999, title={The role of Ag in the pulsed laser growth of YBCO thin films}, volume={85}, ISSN={["0021-8979"]}, DOI={10.1063/1.370172}, abstractNote={We have studied systematically the role of silver in improving microstructure and properties of Y1Ba2Cu3O7−δ (YBCO) thin films. We have more than doubled the grain size to nearly 1.8 μm and reduced processing temperatures by incorporating Ag in the YBCO films, which is accomplished by using a composite target containing 15% by weight of Ag. These films show approximately four times higher Jc than the best films obtained on MgO(001) substrates deposited from stoichiometric Y1Ba2Cu3O7−δ targets. Study of the silver content in the film as a function of the deposition temperature shows clearly a decreasing concentration with increasing temperature and a segregation of the Ag to the surface. The increased oxygen content in the films is also observed at lower processing temperatures, providing strong support for the efficient oxygenation of YBCO via the presence of silver. A qualitative model suggests that the formation of silver oxide, rapid surface diffusion of Ag on MgO surfaces, and the nonreactivity of Ag with YBCO are the key aspects to the improvement in microstructure. The possibility of extending these ideas to the growth of oxides is also discussed, along with the fabrication of in-situ superconducting-metal junctions with 3D geometries.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Kalyanaraman, R and Oktyabrsky, S and Narayan, J}, year={1999}, month={May}, pages={6636–6641} }
 @article{jagannadham_sharma_wei_kalyanraman_narayan_1998, title={Structural characteristics of AIN films deposited by pulsed laser deposition and reactive magnetron sputtering: A comparative study}, volume={16}, ISSN={["0734-2101"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032370406&partnerID=MN8TOARS}, DOI={10.1116/1.581425}, abstractNote={Aluminum nitride films have been deposited on Si(111) substrates at different substrate temperatures using two techniques; pulsed laser deposition or reactive magnetron sputtering. The films deposited by either of the techniques have been characterized by x-ray diffraction and transmission electron microscopy to determine the crystalline quality, grain size, and epitaxial growth relation with respect to the substrate. The bonding characteristics and the residual stresses present in the films have been evaluated using Raman and Fourier transform infrared spectroscopy. Secondary ion mass spectrometry has been performed to determine the nitrogen stoichiometry and the presence of impurities such as oxygen and silicon. The adhesion strength of the AlN films to the silicon substrate and the wear resistance have been determined by scratch test and a specially designed microscopic wear test. A comparison of the different characteristic features associated with the AlN films deposited by pulsed laser deposition or magnetron sputtering is presented with particular emphasis to electronic and tribological applications.}, number={5}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS}, author={Jagannadham, K and Sharma, AK and Wei, Q and Kalyanraman, R and Narayan, J}, year={1998}, pages={2804–2815} }
 @article{kumar_kalyanaraman_vispute_narayan_christen_klabunde_1997, title={Giant magnetoresistance and non-ohmic effects in La0.6Y0.07Ca0.33MnOx thin films}, volume={45}, ISSN={["0921-5107"]}, DOI={10.1016/s0921-5107(96)01975-7}, abstractNote={Transport, magnetoresistance and structural properties of La0.6Y0.07Ca0.03MnOx(LYCMO) thin films grown in situ by pulsed laser ablation have been studied. Transmission electron microscopy and X-ray diffraction measurements have shown that the LYCMO films grow epitaxially on (100) LaAlO3 substrates and are cubic with a lattice parameter of 0.3849 run. The as-deposited films exhibited a metal-insulator transition at 130 K and a giant magnetoresistance at 125 K with a MR ratio (ΔR/RH) of 1500% in 6 Tesla magnetic field. By subsequent annealing of LYCMO films at 900 °C for half an hour in an oxygen ambient, this MR ratio was improved to 3200% at 192 K in the presence of the same magnetic field. This value of the MR ratio is the highest so far reported in this temperature regime. We ascribe this colossal magnetoresistance to the improved magnetic exchange between Mn3+ and Mn4+ ions resulting from the suppressed separation between Mn-O layers caused by a smaller sized Y-cation. We also report a non-ohmic response in the LYCMO films which is observed only in the region of the resistance peak and lends support to a conduction mechanism in these materials based on spin-dependent scattering of electrons.}, number={1-3}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Kumar, D and Kalyanaraman, R and Vispute, RD and Narayan, J and Christen, DK and Klabunde, CE}, year={1997}, month={Mar}, pages={122–125} }
 @article{kalyanaraman_vispute_oktyabrsky_dovidenko_jagannadham_narayan_budai_parikh_suvkhanov_1997, title={Influence of oxygen background pressure on crystalline quality of SrTiO3 films grown on MgO by pulsed laser deposition}, volume={71}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.120011}, DOI={10.1063/1.120011}, abstractNote={We have systematically investigated the effect of oxygen partial pressure (PO2) on the crystalline quality of SrTiO3 films grown on MgO (001) substrates using pulsed laser deposition and established optimized conditions for the growth of high-quality epitaxial films. The crystalline quality is found to improve significantly in the O2 pressure range of 0.5–1 mTorr, compared to the films deposited at higher pressures of 10–100 mTorr. The x-ray diffraction rocking curves for the films grown at PO2 of 1 mTorr and 100 mTorr yielded full width at half-maximum (FWHM) of 0.7° and 1.4°, respectively. The in-plane x-ray φ scans showed epitaxial cube-on-cube alignment of the films. Channeling yields χmin were found to be <5% for the 1 mTorr films and ∼14% for 100 mTorr films. Thermal annealing of the SrTiO3 films in oxygen further improves the quality, and the 1 mTorr films give FWHM of 0.13° and χmin of 1.7%. In-plane misorientations of the annealed SrTiO3 films calculated using results of transmission electron microscopy are ±0.7° for 1 mTorr and ±1.7° for the 10 mTorr film. The high temperature superconducting (high-Tc) Y1Ba2Cu3O7−δ films grown on these SrTiO3/MgO substrates showed a χmin of 2.0% and transition temperature of ∼92 K, indicating that SrTiO3 buffer layers on MgO can be used for growth of high-quality Y1Ba2Cu3O7−δ thin film heterostructures for use in high-Tc devices and next generation microelectronics devices requiring films with high dielectric constants.}, number={12}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Kalyanaraman, R. and Vispute, R. D. and Oktyabrsky, S. and Dovidenko, K. and Jagannadham, K. and Narayan, J. and Budai, J. D. and Parikh, N. and Suvkhanov, A.}, year={1997}, month={Sep}, pages={1709–1711} }
 @article{kumar_oktyabrsky_kalyanaraman_narayan_apte_pinto_manoharan_hegde_ogale_adhi_et al._1997, title={Role of silver doping in oxygen incorporation of oxide thin film}, volume={45}, ISSN={["0921-5107"]}, DOI={10.1016/s0921-5107(96)01920-4}, abstractNote={A distinctive characteristic of silver in oxygen incorporation of oxide thin films during pulsed laser ablation has been discovered. Optical emission spectroscopy studies of laser-induced plume of Ag-target indicates the presence of AgO species whose concentration increases with an increase in oxygen partial pressure. The formation of AgO in laser-plume has been found to be very useful for the realization of high temperature superconducting YBa2Cu3O7−δ (YBCO) and giant magnetoresistive La0.7MnO 3−δ (LMO) thin films with dramatically superior quality if the target materials contained a small amount of silver. The improvement in the quality of these films is brought about by the supply of atomic oxygen to oxide lattices during their formation. This becomes possible due to the fact that Ag, after it is ablated with other constituent materials in the target, gets moderately oxidized in an oxygen atmosphere and the oxidized species dissociate back into Ag and nascent O at the substrate surface. The nascent oxygen is very highly reactive and is easily assimilated into the lattice of these compounds.}, number={1-3}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Kumar, D. and Oktyabrsky, S. and Kalyanaraman, R. and Narayan, Jagdish and Apte, P. R. and Pinto, R. and Manoharan, S. S. and Hegde, M. S. and Ogale, S. B. and Adhi, K. P and et al.}, year={1997}, month={Mar}, pages={55–58} }