@article{gilmore_chattopadhyay_kvit_sharma_lee_collis_sankar_narayan_2003, title={Growth, characterization,, and electrical properties of PbZr0.52Ti0.48O3 thin films on buffered silicon substrates using pulsed laser deposition}, volume={18}, ISSN={["0884-2914"]}, DOI={10.1557/JMR.2003.0016}, abstractNote={Epitaxial thin films of PbZr0.52Ti0.48O3 (PZT) were synthesized successfully on SrRuO3/SrTiO3/MgO/TiN/Si heterostructures by pulsed laser deposition. The films were single phase and had (001) orientation. The deposition parameters were varied to obtain the best epitaxial layer for each of the compounds. Transmission electron microscopy indicated good epitaxy for the entire heterostructure and sharp interfaces between the epilayers. Dielectric and P–E hysteresis loop measurements were carried out with evaporated Ag electrodes. The dielectric constant for the films was found to be between 400–450. The value of saturation polarization Ps was between 55–60 μC/cm2, and the coercive field Ec varied from 60–70 kV/cm. Integration of PZT films with silicon will be useful for future memory and micromechanical devices.}, number={1}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Gilmore, WM and Chattopadhyay, S and Kvit, A and Sharma, AK and Lee, CB and Collis, WJ and Sankar, J and Narayan, J}, year={2003}, month={Jan}, pages={111–114} }
 @misc{narayan_sharma_muth_2003, title={Method for making optoelectronic and microelectronic devices including cubic ZnMgO and/or CdMgO alloys}, volume={6,518,077}, number={2003 Feb. 11}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Narayan, J. and Sharma, A. K. and Muth, J. F.}, year={2003} }
 @article{narayan_sharma_kvit_jin_muth_holland_2002, title={Novel cubic ZnxMg1-xO epitaxial hetero structures on Si (100) substrates}, volume={121}, number={1}, journal={Solid State Communications}, author={Narayan, J. and Sharma, A. K. and Kvit, A. and Jin, C. and Muth, J. F. and Holland, O. W.}, year={2002}, pages={9–13} }
 @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_yamagata_narayan_2001, title={Effect of chamber pressure and atmosphere on the microstructure and nanomechanical properties of amorphous carbon films prepared by pulsed laser deposition}, volume={19}, ISSN={["0734-2101"]}, DOI={10.1116/1.1322641}, abstractNote={We have investigated the effect of chamber pressure and atmosphere on the microstructure and nanomechanical properties of amorphous carbon thin films prepared by pulsed laser deposition. The amorphous carbon films were deposited in various atmospheres such as nitrogen and argon at different chamber pressures. We used Raman spectroscopy to study the bonding characteristics of the deposited amorphous carbon films. Atomic force microscopy and optical microscopy were utilized to observe the surface conditions and the microstructures of the deposited films. Nanoindentation measurements were carried out on various samples prepared under different conditions to study the effect of chamber pressure and atmosphere on the elastic modulus and nanohardness of the films. It was found that reduced vacuum leads to formation of amorphous carbon films with reduced elastic modulus and nanohardness. Amorphous carbon films prepared under higher chamber pressures exhibit an increased density of particulates and significantly roughened surface. The results were understood in combination with the optical emission and electrostatic measurements of the laser plasma plume. It was found that the presence of atmosphere decreases the leading edge ionic energies of the species in the laser plasma plume and increases the thermalization of the laser plasma due to an increased possibility of collision.}, number={1}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS}, author={Wei, Q and Sankar, J and Sharma, AK and Yamagata, Y and Narayan, J}, year={2001}, pages={311–316} }
 @article{kumar_narayan_kvit_sharma_sankar_2001, title={High coercivity and superparamagnetic behavior of nanocrystalline iron particles in alumina matrix}, volume={232}, ISSN={["1873-4766"]}, DOI={10.1016/S0304-8853(01)00191-3}, abstractNote={Single-domain nanoscale magnetic iron particles have been embedded uniformly in an amorphous matrix of alumina using a pulsed laser deposition technique. Structural characterization by transmission electron microscopy (TEM) reveals the presence of a crystalline iron and an amorphous alumina phase. Fine particle magnetism have been investigated by carrying out field and temperature dependence of magnetization measurements using superconducting quantum interference device magnetometer. The particle size of Fe in Al2O3 matrices prepared by changing the deposition time of Fe, have been found to be 9, 7 and 5 nm from TEM studies. At 10 K, the coercivities of these samples are found be 450, 350 and 150 Oe, respectively. At 300 K, the coercivity of Fe–Al2O3 sample decreases from 100 to 50 Oe as the particle size decreases from 9 to 7 nm and finally the sample turns superparamagnetic when the Fe particle size becomes around 5 nm. Based on the calculated value of blocking temperature, TB, (481 K), magnetic anisotropy K (4.8×105 erg/cm3) for Fe, and the Boltzmann constant kB (1.38×10−16 erg/K) from TB=KV/25kB, the mean radius of Fe particles is found to be 9.3 nm. in one of the samples. This is in good agreement with the particle size measured using TEM studies.}, number={3}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Kumar, D and Narayan, J and Kvit, AV and Sharma, AK and Sankar, J}, year={2001}, month={Jul}, pages={161–167} }
 @article{wang_sharma_kvit_wei_zhang_koch_narayan_2001, title={Mechanical properties of nanocrystalline and epitaxial TiN films on (100) silicon}, volume={16}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.2001.0373}, abstractNote={We investigated mechanical properties of TiN as a function of microstructure varying from nanocrystalline to single crystal TiN films deposited on (100) silicon substrates. By varying the substrate temperature from 25 to 700 °C during pulsed laser deposition, the microstructure of TiN films changed from nanocrystalline (having a uniform grain size of 8 nm) to a single crystal epitaxial film on the silicon (100) substrate. The microstructure and epitaxial nature of these films were investigated using x-ray diffraction and high-resolution transmission electron microscopy. Hardness measurements were made using nanoindentation techniques. The nanocrystalline TiN contained numerous triple junctions without any presence of amorphous regions. The width of the grain boundary remained constant at less than 1 nm as a function of boundary angle. Similarly the grain boundary structure did not change with grain size. The hardness of TiN films decreased with decreasing grain size. This behavior was modeled recently involving grain boundary sliding, which is particularly relevant in the case of hard materials such as TiN.}, number={9}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Wang, H and Sharma, A and Kvit, A and Wei, Q and Zhang, X and Koch, CC and Narayan, J}, year={2001}, month={Sep}, pages={2733–2738} }
 @article{kumar_chattopadhyay_gilmore_lee_sankar_kvit_sharma_narayan_pietambaram_singh_et al._2001, title={Structural and magnetoresistance properties of La2/3Ca1/3MnO3 thin films on buffered silicon substrates}, volume={78}, ISSN={["0003-6951"]}, DOI={10.1063/1.1350603}, abstractNote={We report an epitaxial growth of LCMO (La2/3Ca1/3MnO3) film on Si by using a highly conducting diffusion barrier layer of TiN. In order to achieve epitaxial growth of LCMO films, MgO, and SrTiO3 films were used as intermediate layers between LCMO and TiN layers. The results have indicated that the properties of LCMO films on Si substrates, deposited under an optimized condition, are on par with the properties of LCMO films on conventional oxide substrates such as LaAlO3 and SrTiO3 in terms of paramagnetic to ferromagnetic transition temperature, insulator to metal transition temperature, and magnetoresistance ratio.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Kumar, D. and Chattopadhyay, S. and Gilmore, W. M. and Lee, C. B. and Sankar, J. and Kvit, A. and Sharma, A. K. and Narayan, Jagdish and Pietambaram, S. V. and Singh, R. K. and et al.}, year={2001}, month={Feb}, pages={1098–1100} }
 @article{kumar_narayan_nath_sharma_kvit_jin_2001, title={Tunable magnetic properties of metal ceramic composite thin films}, volume={119}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(01)00213-7}, abstractNote={We have developed a novel thin film processing method based upon pulsed laser deposition to process nanocrystalline magnetic materials with accurate size and interface control. Using this method, single domain nanocrystalline Fe and Ni particles in 5–10 nm size range embedded in amorphous as well as crystalline alumina have been produced. Magnetization measurements of these layered thin films as function of field and temperature were carried out using a superconducting quantum interference device magnetometer. The size of Fe and Ni nanodots measured using transmission electron microscopy and calculated using magnetic data are in excellent agreement with each other.}, number={2}, journal={SOLID STATE COMMUNICATIONS}, author={Kumar, D and Narayan, J and Nath, TK and Sharma, AK and Kvit, A and Jin, C}, year={2001}, pages={63–66} }
 @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{yamagata_sharma_narayan_mayo_newman_ebihara_2000, title={Comparative study of pulsed laser ablated plasma plumes from single crystal graphite and amorphous carbon targets. Part I. Optical emission spectroscopy}, volume={88}, ISSN={["0021-8979"]}, DOI={10.1063/1.1321783}, abstractNote={A comparative study of ablation plasma plumes originated from single crystal graphite (SCG) and amorphous carbon (a-C) targets during the preparation of diamond-like carbon (DLC) films by KrF excimer pulsed laser deposition (PLD) has been carried out by means of a monochromator equipped with an intensified optical multichannel analyzer. In high vacuum, the emission lines of carbon neutral C and ions of C+, C2+, and C3+ can be observed from both the SCG and a-C plasma plumes. The emission intensity from C atoms increases with laser energy density (EL) increase for both cases. The C2 emission intensity from the SCG plasma plume changes drastically with EL, while that from the a-C plasma plume is almost constant. The C2/C emission intensity ratio for the a-C case decreases with EL increase. As for the SCG case, the C2/C ratio decreases with EL increase up to 3.0 J/cm2, and increases slightly with further EL increase. Nanohardness of the deposited films decreases with the increase of the C2/C emission intensity ratio. It is suggested that for both the SCG and a-C target cases, the C2 molecule in the ablated plasma plume may not play an important role in producing high quality DLC films. It is further proposed that the threshold of laser fluence for the formation of diamond-like character film using KrF excimer PLD is 2.1 J/cm2(0.84×108 W/cm2) for the a-C target and 3.0 J/cm2(1.2×108 W/cm2) for the SCG target. The C2 vibrational temperature of the SCG and the a-C plasma plumes show different features on both the laser energy density and nitrogen pressure dependencies. Through optical emission spectroscopy and Langmuir probe measurements in vacuum and nitrogen background, it is concluded that there are many particles with higher mass in the SCG plasma plume, especially at relatively lower laser energy density below 3.0 J/cm2.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Yamagata, Y and Sharma, A and Narayan, J and Mayo, RM and Newman, JW and Ebihara, K}, year={2000}, month={Dec}, pages={6861–6867} }
 @article{mayo_newman_yamagata_sharma_narayan_2000, title={Comparative study of pulsed laser ablated plasma plumes from single crystal graphite and amorphous carbon targets. Part II. Electrostatic probe measurements}, volume={88}, ISSN={["0021-8979"]}, DOI={10.1063/1.1321784}, abstractNote={In an ongoing effort to investigate plasma plume features yielding high quality diamond-like carbon films, we have applied plasma plume diagnosis and film characterization to examine plume character distinction from KrF laser ablation of both amorphous carbon (a-C) and single crystal graphite (SCG) targets. The advancing plasma plume produced by these structurally different targets are observed to possess quantitatively similar total heavy particle inventory, ionized fraction, and electron thermal content, yet quite different ion kinetic energy, plume profile, C2 formation mechanism, and concentration of complex molecules. Plume electron temperatures are observed to reside in the range 1–3 eV, with those in SCG plumes ∼10%–30% greater than a-C at all spatial positions downstream of the target. For both target cases, we find Te drop off with position away from the target with radiation as the most likely loss mechanism for these noninteracting plumes propagating in vacuum. Electron density is found to be ∼10%–12% lower near the target in SCG than a-C plumes consistent with mass loss inventory measurements, whereas ion fractions are estimated in the range ∼10%–15% for both target cases. All recorded data support the conclusion that the SCG target plasma plume is populated with heavier, more complex molecules than those in a-C which have been shown to be predominantly comprised of C and C+ under vacuum conditions with the addition of C2 at high fill pressure. A significantly smaller profile peaking factor for SCG plumes supports this conclusion. Less energetic and slightly lower temperature SCG plume conditions are consistent with reduced peaking and more massive plume species. Plasma plumes from SCG targets exhibit laser energy (El) dependent peaking, again consistent with more complex molecules increasingly disassociated with El increase. The El dependence further suggests the potential for control of particle size distribution and plume profile peaking, though not independently. Consistent with this scenario is the observation of harder films produced from SCG targets at lower El. Micro-Raman results indicate strongly heterogeneous films deposited by SCG target ablation even under vacuum conditions further supporting the case for more complex structures with greater hardness. Energy balance estimates indicate that ion kinetic energy dominates the balance and that SCG ablation liberates about twice the number of C12 atoms from the target per unit El. As well, high pressure background fill indicates lesser plume energy attenuation for SCG plumes, again suggesting the presence of higher mass particles.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Mayo, RM and Newman, JW and Yamagata, Y and Sharma, A and Narayan, J}, year={2000}, month={Dec}, pages={6868–6874} }
 @article{sharma_narayan_jin_kvit_chattopadhyay_lee_2000, title={Integration of Pb(Zr0.52Ti0.48)O-3 epilayers with Si by domain epitaxy}, volume={76}, ISSN={["1077-3118"]}, DOI={10.1063/1.126063}, abstractNote={High-quality lead zirconate titanate films (PZT) have been grown on yttrium barium copper oxide (YBCO) bottom electrode by domain epitaxy where integral multiples of lattice constants match across the interface. The YBCO films were epitaxially fabricated on Si (100) by introducing epilayer geometry of strontium titanate/magnesium oxide/titanium nitride. Pulsed-laser ablation was used to evaporate these five stoichiometric targets in a high vacuum chamber. X-ray diffraction and high-resolution transmission electron microscopy techniques were employed to gain understanding of the structure, crystallinity, and interfaces in these epilayers. The electrical characterization of the PZT films with evaporated silver contacts resulted in superior values of spontaneous polarization, remnant polarization, and coercive fields. This heterostructure opens a way for integration of epitaxial single-crystal PZT-based capacitors with silicon-based devices.}, number={11}, journal={APPLIED PHYSICS LETTERS}, author={Sharma, AK and Narayan, J and Jin, C and Kvit, A and Chattopadhyay, S and Lee, C}, year={2000}, month={Mar}, pages={1458–1460} }
 @misc{narayan_sharma_muth_2000, title={Optoelectronic and microelectronic devices including cubic ZnMgO and/or CdMgO alloys}, volume={6,423,983}, number={2000 Oct. 13}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Narayan, J. and Sharma, A. K. and Muth, J. F.}, year={2000} }
 @article{teng_muth_kolbas_hassan_sharma_kvit_narayan_2000, title={Quantum confinement of E-1 and E-2 transitions in Ge quantum dots embedded in an Al2O3 or an AlN matrix}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.125650}, abstractNote={Alternating layers of Ge quantum dots embedded in either Al2O3 or AlN matrices were deposited on sapphire substrates by pulsed-laser deposition. The characteristics of the dots are shown to be independent of the surrounding matrix. The dots size (73, 130, 160, and 260 ű5%) was controlled by the laser energy density and deposition time, and was characterized by high-resolution transmission electron microscopy. The dots were single crystalline with no apparent GeOx interfacial layers. Transmission spectroscopy at room temperature and 77 K was used to probe the above-band-edge absorption of the Ge nanodots. The spectral positions of both E1/E1+Δ1 and E2 transitions were found to shift to higher energy in the absorption spectra with decreasing nanodot sizes. This indicates that strong quantum-confinement effect permits the optical properties of Ge dots to be modified in a controlled manner.}, number={1}, journal={APPLIED PHYSICS LETTERS}, author={Teng, CW and Muth, JF and Kolbas, RM and Hassan, KM and Sharma, AK and Kvit, A and Narayan, J}, year={2000}, month={Jan}, pages={43–45} }
 @inproceedings{teng_muth_kolbas_hassan_sharma_narayan_2000, title={Quantum confinement of E1 and E2 transitions in Ge quantum dots embedded in Al203 or an AlN matrix}, booktitle={Optical microstructural characterization of semiconductors  (Materials Research Society proceedings, vol. 588)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Teng, C. W. and Muth, J. F. and Kolbas, R. M. and Hassan, K. M. and Sharma, A. K. and Narayan, J.}, editor={J. Piqueras, T. Sekiguchi and Unlu, M. S.Editors}, year={2000} }
 @article{teng_muth_ozgur_bergmann_everitt_sharma_jin_narayan_2000, title={Refractive indices and absorption coefficients of MgxZn1-xO alloys}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.125912}, abstractNote={Indices of refraction for MgxZn1−xO epitaxial films grown by pulsed-laser deposition on sapphire substrates with x up to 0.36 were determined in the range of wavelength 457–968 nm by analysis of optical transmission spectra and prism-coupled waveguide measurements. The dispersion follows the first-order Sellmeier dispersion equation. Absorption coefficients, exciton energy gaps, and binding energies of MgxZn1−xO alloys were determined by transmission spectroscopy. The excitonic absorption features were clearly visible at room temperature despite alloy broadening. These results provide important information for the design and modeling of ZnO/MgZnO heterostructure optoelectronic devices.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Teng, CW and Muth, JF and Ozgur, U and Bergmann, MJ and Everitt, HO and Sharma, AK and Jin, C and Narayan, J}, year={2000}, month={Feb}, pages={979–981} }
 @inproceedings{hassan_sharma_narayan_muth_teng_kolbas_2000, title={Size effect in germanium nanostructures fabricated by pulsed laser deposition}, booktitle={Nanophase and Nanocomposite Materials III  (Materials Research Society proceedings; vol. 581)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Hassan, K. M. and Sharma, A. K. and Narayan, J. and Muth, J. F. and Teng, C. W. and Kolbas, R. M.}, editor={H. Hahn, S. Komarneni and Parker, J. C.Editors}, year={2000} }
 @inproceedings{sharma_jin_narayan_teng_muth_kolbas_holland_2000, title={Structural and optical property investigations on Mg-Alloying in epitaxial zinc oxide films on sapphire}, number={2000}, booktitle={MRS Internet Journal of Nitride Semiconductor Research}, author={Sharma, A. K. and Jin, C. and Narayan, J. and Teng, C. W. and Muth, J. F. and Kolbas, R. M. and Holland, O. W.}, year={2000} }
 @article{sharma_narayan_narayan_jagannadham_2000, title={Structural and tribological characteristics of diamond-like carbon films deposited by pulsed laser ablation}, volume={77}, ISSN={["0921-5107"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0034250566&partnerID=MN8TOARS}, DOI={10.1016/s0921-5107(00)00434-7}, abstractNote={Diamond-like carbon (DLC) films were deposited by pulsed laser ablation (PLA) on Si (100) and Ti–6Al–4V alloy substrates at four different temperatures. The bonding characteristics of the films were studied by X-ray photoelectron (XPS) and Raman spectroscopy techniques. The ratio of tetrahedral to trigonally coordinated carbon atoms was estimated by XPS successfully. The fraction of tetrahedrally bonded atoms in the films deposited on Si at room temperature was estimated to be ∼63 at.% which decreased to ∼33 at.% as the substrate temperature increased to 400°C. The Raman spectroscopy results of these specimens agree qualitatively with these observations. Also, using Raman spectroscopy, the residual compressive stress was also estimated in fully adherent films on Si substrate to be ∼3 GPa with reference to the value of stress present in a free-standing peeled off film from the Ti-alloy substrate. This value is consistent with the residual stresses estimated in the earlier results. The abrasive wear rates have been correlated during the initial stages of the well adhered films with the sp3/sp2 ratios. The importance of suitable dopants and the interfacial interlayers in reducing internal compressive stresses in these films is discussed.}, number={2}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Sharma, AK and Narayan, RJ and Narayan, J and Jagannadham, K}, year={2000}, month={Aug}, pages={139–143} }
 @article{mayo_newman_sharma_yamagata_narayan_1999, title={Electrostatic measurement of plasma plume characteristics in pulsed laser evaporated carbon}, volume={86}, ISSN={["0021-8979"]}, DOI={10.1063/1.371135}, abstractNote={A triple Langmuir probe measurement has been implemented to investigate plasma plume character in low fluence (∼3.0 J/cm2) pulsed laser evaporation (PLE) discharges and has been found to be an extremely valuable tool. Absolute plasma plume density estimates are found to reside in the range 1.0×1013–2.0×1014 cm−3 for vacuum pulses. A simple heavy particle streaming model for vacuum pulses allows estimates of the plume ionization fraction of ∼10%. This is consistent with typical deposition inventory suggesting that high kinetic energy ions may play an important role in diamond-like carbon (DLC) film deposition. Electron temperature inferred from the electrostatic probe is found to consistently reside in the range 0.5–3.0 eV, and appears to be uninfluenced by operating conditions and large variations in Ar and N2 fill gas pressure. Consistent with strong plume ion and neutral particle coupling to the background fill, constancy of Te suggests expulsion of background gas by the energetic plume. The leading edge ion plume speed is measured via temporal displacement of spatially separated probe signals on consecutive PLE pulses. Flow speeds as high as 5.0×104 m/s are observed, corresponding to ∼156 eV in C+. The ion flow speed is found to be a strongly decreasing function of fill pressure from an average high of ∼126 eV in vacuum to ∼0.24 eV at 600 mTorr N2. Raman scattering spectroscopy indicates DLC film quality also degrades with fill pressure suggesting the importance of high ion kinetic energy in producing good quality films, consistent with earlier work demonstrating the importance of energetic particles. Optical emission indicates an increase in C2 molecular light intensity with fill gas pressure implying a reduced, if any, role of these species in DLC production. Ion current signal anomalies are often seen during high pressure pulses. It is suggested that this may indicate the formation of high mass carbon clusters during plume evolution in the presence of background gas. Mass diffusivity estimates, based on density decay, suggest the presence of C2+ under these conditions. Demonstration and control of such cluster formation may provide method(s) for controlling novel advanced materials properties.}, number={5}, journal={JOURNAL OF APPLIED PHYSICS}, author={Mayo, RM and Newman, JW and Sharma, A and Yamagata, Y and Narayan, J}, year={1999}, month={Sep}, pages={2865–2871} }
 @article{sharma_kvit_narayan_1999, title={Growth of single crystal MgO on TiN/Si heterostructure by pulsed laser deposition}, volume={17}, ISSN={["0734-2101"]}, DOI={10.1116/1.582071}, abstractNote={High quality epitaxial films of MgO have been grown on a Si (100) surface with TiN as a buffer layer by pulsed laser deposition. The electron diffraction patterns of these films confirmed the single crystal nature of the films with cube-on-cube epitaxy. It is difficult to grow high quality MgO films directly on Si due to large differences in lattice constants and thermal expansion coefficients of the two materials. The high resolution microscopy on our films revealed sharp interfaces between MgO/TiN and TiN/Si with no indication of interfacial reaction. Raman spectrum of MgO films revealed sharp peaks characteristic of MgO and TiN, indicating a good crystallinity. Further, superconducting YBa2Cu3O7−x films were grown on this heterostructure with a sharp transition at 88 K, indicating a high quality of the grown structure. This work opens a way for the growth of a variety of high quality perovskite structures for integration with silicon devices.}, number={6}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS}, author={Sharma, AK and Kvit, A and Narayan, J}, year={1999}, pages={3393–3396} }
 @article{wei_sharma_sankar_narayan_1999, title={Mechanical properties of diamond-like carbon composite thin films prepared by pulsed laser deposition}, volume={30}, ISSN={["1879-1069"]}, DOI={10.1016/S1359-8368(99)00035-9}, abstractNote={We have investigated the mechanical properties of diamond-like carbon (DLC) thin films that contain foreign atoms. The DLC films were prepared by pulsed laser deposition. A novel target design was adopted to incorporate foreign atoms into the DLC films during film deposition. Copper, titanium and silicon are chosen as the dopants. The chemical composition of the doped films was determined using Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy and calibrated extrapolation. Experimental results of both visible and UV Raman are presented and discussed in terms of peak shape and position. The effect of dopants on the Raman spectrum is also analyzed. Optical microscopy of the pure DLC of a certain thickness showed severe buckling. A brief review of the theoretical background of adhesion is given and the possible mechanisms of adhesion that may work in DLC coatings are discussed. Qualitative scratch tests on the specimens show that pure DLC has quite poor adhesion due to the large compressive stress, while the doped DLC films exhibit much improved adhesion. Wear tests show improved wear resistance in the doped DLC coatings. Nanoindentation results give an average hardness above 40 GPa and effective Young's modulus above 200 GPa for pure DLC. The copper doped DLC films showed slightly decreased hardness and Young's modulus as compared to pure DLC films. Ti and Si can reduce the hardness and Young's modulus more than Cu. All these can be understood by analyzing the internal stress reduction as derived from Raman G-peak shift to lower wavenumbers. A preliminary model of the stress reduction mechanism is discussed.}, number={7}, journal={COMPOSITES PART B-ENGINEERING}, author={Wei, Q and Sharma, AK and Sankar, J and Narayan, J}, year={1999}, pages={675–684} }
 @article{sharma_narayan_muth_teng_jin_kvit_kolbas_holland_1999, title={Optical and structural properties of epitaxial MgxZn1-xO alloys}, volume={75}, ISSN={["1077-3118"]}, DOI={10.1063/1.125340}, abstractNote={The optical and structural properties of high-quality single-crystal epitaxial MgZnO films deposited by pulsed-laser deposition were studied. In films with up to ∼36 at. % Mg incorporation, we have observed intense ultraviolet band edge photoluminescence at room temperature and 77 K. The highly efficient photoluminescence is indicative of the excitonic nature of the material. Transmission spectroscopy was used to show that the excitonic structure of the alloys was clearly visible at room temperature. High-resolution transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectroscopy/ion channeling were used to verify the epitaxial single-crystal quality of the films and characterize the defect content. Post-deposition annealing in oxygen was found to reduce the number of defects and to improve the optical properties of the films. These results indicate that MgZnO alloys have potential applications in a variety of optoelectronic devices.}, number={21}, journal={APPLIED PHYSICS LETTERS}, author={Sharma, AK and Narayan, J and Muth, JF and Teng, CW and Jin, C and Kvit, A and Kolbas, RM and Holland, OW}, year={1999}, month={Nov}, pages={3327–3329} }
 @article{hassan_sharma_narayan_muth_teng_kolbas_1999, title={Optical and structural studies of Ge nanocrystals embedded in AlN matrix fabricated by pulsed laser deposition}, volume={75}, ISSN={["1077-3118"]}, DOI={10.1063/1.124648}, abstractNote={We have fabricated Ge nanostructures buried in a matrix of AlN grown on Si(111) by pulsed laser deposition at the substrate temperature of 500 °C. The characterization of these structures was performed using high-resolution transmission electron microscopy (HRTEM), photoluminescence, and Raman spectroscopy. The HRTEM results show that the Ge islands are single crystal with a pyramidal shape. The average size of Ge islands was determined to be ∼15 nm, which could be varied by controlling laser deposition and substrate parameters. The Raman spectrum showed a peak of the Ge–Ge vibrational mode downward shifted up to 295 cm−1 which is caused by quantum confinement of phonons in the Ge dots. The photoluminescence of the Ge dots (size ∼15 nm) was blueshifted by ∼0.266 eV from the bulk Ge value of 0.73 eV at 77 K, resulting in a distinct peak at ∼1.0 eV. The transmission measurements carried out on different samples having Ge dot sizes of 7, 8, and 13 nm deposited on sapphire substrate showed the above band edge transitions of Ge, which were also blueshifted in accordance with the quantum confinement effect. The importance of pulsed laser deposition in fabricating novel nanostructures is emphasized.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Hassan, KM and Sharma, AK and Narayan, J and Muth, JF and Teng, CW and Kolbas, RM}, year={1999}, month={Aug}, pages={1222–1224} }
 @article{yamagata_sharma_narayan_mayo_newman_ebihara_1999, title={Optical emission study of ablation plasma plume in the preparation of diamond-like carbon films by KrF excimer laser}, volume={86}, ISSN={["0021-8979"]}, DOI={10.1063/1.371340}, abstractNote={Optical emission study of the laser ablation plasma plume during the preparation of diamond-like carbon (DLC) films using KrF excimer (248 nm) pulsed laser deposition (PLD) has been carried out by means of a monochromator equipped with an intensified optical multichannel analyzer. In high vacuum (1×10−7 Torr), the emission lines from carbon ions of C+, C2+, and C3+ are observed in addition to atomic carbon emission lines, while no emission from the diatomic carbon molecule (C2) is observed. With increasing background nitrogen pressure up to 500 mTorr, the emission intensities of the C2 Swan band and the carbon nitride (CN) violet band increase. The diamond-like character of deposited DLC film degrades with background nitrogen pressure. The vibrational temperature of C2 and CN molecules decreases with the increasing of nitrogen pressure. The CN vibrational temperature for the first 2 μs after the laser pulse is very high and in agreement with the kinetic energy of monatomic carbon ions. The C2 vibrational temperature is as low as 0.6 eV and is consistent with the electron temperature of about 0.8–3.0 eV. It is conjectured that CN molecules are formed directly in reactions involving energetic ionic monatomic carbon, and that the formation of excited C2 molecules is the result of molecular recombinations of C atoms and ions. From the emission intensity measurements and the estimation of the vibrational temperature, it is suggested that the C2 molecule in the ablated plasma plume is not important, but energetic species, such as C+, are very important for producing high quality DLC films using PLD.}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={Yamagata, Y and Sharma, A and Narayan, J and Mayo, RM and Newman, JW and Ebihara, K}, year={1999}, month={Oct}, pages={4154–4159} }
 @article{wei_narayan_sharma_sankar_narayan_1999, title={Preparation and mechanical properties of composite diamond-like carbon thin films}, volume={17}, ISSN={["0734-2101"]}, DOI={10.1116/1.582074}, abstractNote={We have investigated mechanical properties of diamond-like carbon (DLC) thin films, particularly the internal compressive stress and ways to alleviate it. Foreign atoms such as copper, titanium, and silicon were incorporated into the DLC films during pulsed laser deposition. The chemical composition of the doped films was determined using Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy (XPS). Optical microscopy of the doped films showed that DLC films containing Cu exhibit much less particulate density as compared to the films containing Ti and Si. Visible Raman spectroscopy was used to characterize the films. The effect of dopants on the Raman spectrum was analyzed in terms of peak shape and position. Optical microscopy of the pure DLC of a certain thickness showed severe buckling. The mechanisms of adhesion associated with DLC coatings were discussed. Qualitative scratch tests on the specimens showed that pure DLC films have relatively poor adhesion due to a large compressive stress, while the doped DLC films exhibit much improved adhesion. Wear tests show improved wear resistance in the doped DLC coatings. Nanoindentation results suggest that pure DLC has an average hardness above 40 GPa and effective Young’s modulus above 200 GPa. The doped DLC films showed slightly decreased hardness and Young’s modulus as compared to pure DLC films. These results can be rationalized by analyzing the internal stress reduction as derived from Raman G-peak shift to lower wavenumbers. A preliminary interpretation of the stress reduction mechanism is discussed.}, number={6}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS}, author={Wei, Q and Narayan, RJ and Sharma, AK and Sankar, J and Narayan, J}, year={1999}, pages={3406–3414} }
 @inproceedings{teng_muth_kolbas_hassan_sharma_kvit_narayan_1999, title={Quantum confinement of above-band-bap transitions in Ge quantum dots embedded in an Al2O3 or AIN matrix}, booktitle={Optical microstructural characterization of semiconductors  (Materials Research Society proceedings, vol. 588)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Teng, C. W. and Muth, J. F. and Kolbas, R. M. and Hassan, K. M. and Sharma, A. K. and Kvit, A. and Narayan, J.}, editor={J. Piqueras, T. Sekiguchi and Unlu, M. S.Editors}, year={1999} }
 @article{godbole_dovidenko_sharma_narayan_1999, title={Thermal reactions and micro-structure of TiN-AlN layered nano-composites}, volume={68}, ISSN={["0921-5107"]}, DOI={10.1016/s0921-5107(99)00154-3}, abstractNote={Bilayer and multilayer structures of TiN and AlN thin films were synthesized using pulsed laser deposition technique in a substrate temperature range 300–700°C. The chemical reactions at TiN–AlN interfaces and the formation of different alloy phases were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was observed that TiN–AlN interface remains sharp and stable for deposition temperatures up to ∼650°C. At higher deposition temperatures, however, substantial chemical reactions were found to occur. The ternary alloy phases such as Ti3Al2N2 and Ti3AlN have been observed, for the first time. The composites synthesized at temperatures lower than 650°C and subsequently annealed at higher temperature were found to exhibit very limited or no interfacial chemical reactions. The effect of layer thickness on the microstructure is also studied. The studies revealed that by controlling the thickness of individual layers and substrate temperatures, it was possible to control microstructure and obtain composite coatings consisting of ternary Ti–Al–N alloy phases. The results are discussed in terms of characteristic features of pulsed laser ablation process in which evaporated flux contains energetic ions, electrons and neutral particles. Preliminary nano-indentation measurements and oxidation measurements reveal that these composites possess desirable mechanical properties at high temperatures.}, number={2}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Godbole, VP and Dovidenko, K and Sharma, AK and Narayan, J}, year={1999}, month={Dec}, pages={85–90} }
 @inproceedings{hassan_sharma_narayan_muth_teng_kolbas_1998, title={Germanium nanostructures fabricated by pulsed laser deposition}, booktitle={Microcrystalline and nanocrystalline semiconductors--1998: symposium held November 30-December 3, 1998, Boston, Massachusetts, U.S.A.}, author={Hassan, K. M. and Sharma, A. K. and Narayan, J. and Muth, J. F. and Teng, C. W. and Kolbas, R. M.}, year={1998} }
 @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} }