@article{narayan_oktyabrsky_2002, title={Formation of misfit dislocations in thin film heterostructures}, volume={92}, ISSN={["0021-8979"]}, DOI={10.1063/1.1521789}, abstractNote={We have studied characteristics of 60° and 90° dislocations in GaAs/Si(100) thin-film heterostructures grown by metal-organic chemical-vapor deposition at 650 °C. The misfit dislocation network consists of approximately 60% of 90° dislocations, and 40% of the closely spaced pairs of 60° dislocations with intersecting glide planes. This ratio has remained essentially constant after rapid thermal annealing at 800 °C for 90 sec. It is envisaged that these 60° dislocation pairs have parallel screw components and as a result they cannot combine to form a 90° dislocation. Upon annealing, some of the 60° dislocation pairs split to form stacking faults in agreement with our earlier model. Based upon these observations, we propose a model where a first set of 60° dislocations is generated from the undulated surface above a critical thickness. The second set of 60° dislocations is nucleated at a larger thickness and at the smoother surface. The Burgers vectors of these dislocations are controlled by the dislocations from the first set, and only low-energy dislocation pairs are formed through glide towards the interface and later through short glide and climb along the interface plane. We have used a numerical analysis based on elasticity theory to evaluate the changes in the nucleation barrier for the 60° dislocations caused by the interaction with the existing misfit dislocations.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Narayan, J and Oktyabrsky, S}, year={2002}, month={Dec}, pages={7122–7127} }
 @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{wei_sankar_sharma_oktyabrsky_narayan_narayan_2000, title={Atomic structure, electrical properties, and infrared range optical properties of diamondlike carbon films containing foreign atoms prepared by pulsed laser deposition}, volume={15}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.2000.0094}, abstractNote={We investigated the atomic structure, electrical, and infrared range optical properties of diamondlike carbon (DLC) films containing alloy atoms (Cu, Ti, or Si) prepared by pulsed laser deposition. Radial distribution function (RDF) analysis of these films showed that they are largely sp3 bonded. Both pure DLC and DLC + Cu films form a Schottky barrier with the measuring probe, whereas DLC + Ti films behave like a linear resistor. Pure DLC films and those containing Cu exhibit p-type conduction, and those containing Ti and Si have n-type conduction. Photon-induced conduction is observed for pure DLC, and the mechanism is discussed in terms of low-density gap states of highly tetrahedral DLC. Our results are consistent with relative absence of gap states in pure DLC, in accordance with theoretical prediction by Drabold et al.37 Temperature dependence of conductivity of DLC + Cu shows a behavior σ ∞ exp(−B/T1/2), instead of the T−1/4 law (Mott–Davis law). Contributions from band-to-band transitions, free carriers, and phonons to the emissivity spectrum are clearly identified in pure DLC films. The amorphous state introduces a large contribution from localized states. Incorporation of a small amount of Si in the DLC does not change the general feature of emissivity spectrum but enhances the contribution from the localized states. Cu and Ti both enhance the free carrier and the localized state contributions and make the films a black body.}, number={3}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Wei, Q and Sankar, J and Sharma, AK and Oktyabrsky, S and Narayan, J and Narayan, RJ}, year={2000}, month={Mar}, pages={633–641} }
 @article{oktyabrsky_dovidenko_sharma_narayan_joshkin_1999, title={Cubic GaN formation under nitrogen-deficient conditions}, volume={74}, ISSN={["0003-6951"]}, DOI={10.1063/1.123882}, abstractNote={We have studied crystal structure and associated defects in GaN/α-Al2O3 (0001) films grown under nitrogen-deficient conditions by metalorganic chemical vapor deposition and pulsed laser deposition. N-deficient films exhibit polycrystalline structure with a mixture of cubic zinc-blende and wurtzite hexagonal GaN grains retaining tetragonal bonding across the boundaries and hence the epitaxial orientations and polarity. Renucleation of the wurtzite phase at different {111} planes of cubic GaN results in a rough and faceted surface of the film. We elucidate that the cubic phase is more stable under the nitrogen deficiency.}, number={17}, journal={APPLIED PHYSICS LETTERS}, author={Oktyabrsky, S and Dovidenko, K and Sharma, AK and Narayan, J and Joshkin, V}, year={1999}, month={Apr}, pages={2465–2467} }
 @article{muth_kolbas_sharma_oktyabrsky_narayan_1999, title={Excitonic structure and absorption coefficient measurements of ZnO single crystal epitaxial films deposited by pulsed laser deposition}, volume={85}, ISSN={["1089-7550"]}, DOI={10.1063/1.370601}, abstractNote={The optical properties of high quality single crystal epitaxial zinc oxide thin films grown by pulsed laser deposition on c-plane sapphire substrates were studied. It was found that annealing the films in oxygen dramatically improved the optical and electrical properties. The absorption coefficient, band gap, and exciton binding energies were determined by transmission measurements and photoluminescence. In both the annealed and the as-deposited films excitonic absorption features were observed at both room temperature and 77 K. In the annealed films the excitonic absorption peaks were substantially sharper and deep level photoluminescence was suppressed.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Muth, JF and Kolbas, RM and Sharma, AK and Oktyabrsky, S and Narayan, J}, year={1999}, month={Jun}, pages={7884–7887} }
 @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} }
 @inproceedings{sharma_dovidenko_oktyabrsky_moxey_muth_kolbas_narayan_1998, title={Growth of high quality single crystal ZnO films on sapphire by pulsed laser ablation}, booktitle={Advances in laser ablation of materials: Symposium held April 13-16, 1998, San Francisco, California, U.S.A.  (Materials Research Society symposia proceedings ; v. 526).}, publisher={Warrendale, Pa.: Materials Research Society}, author={Sharma, A. K. and Dovidenko, K. and Oktyabrsky, S. and Moxey, D. E. and Muth, J. F. and Kolbas, R. M. and Narayan, J.}, year={1998}, pages={305} }
 @inproceedings{wei_sharma_narayan_ravindra_oktyabrsky_sankar_muth_kolbas_narayan_1998, title={Microstructure and IR range optical properties of pure DLC and DLC containing dopants prepared by pulsed laser deposition}, booktitle={Advances in laser ablation of materials: Symposium held April 13-16, 1998, San Francisco, California, U.S.A.  (Materials Research Society symposia proceedings ; v. 526).}, publisher={Warrendale, Pa.: Materials Research Society}, author={Wei, Q. and Sharma, A. K. and Narayan, R. J. and Ravindra, N. M. and Oktyabrsky, S. and Sankar, J. and Muth, J. F. and Kolbas, R. M. and Narayan, J.}, year={1998}, pages={331} }
 @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} }