@article{govindaraju_aleksov_li_okuzumi_wolter_collazo_prater_sitar_2006, title={Comparative study of textured diamond films by thermal conductivity measurements}, volume={85}, ISSN={["1432-0630"]}, DOI={10.1007/s00339-006-3697-7}, number={3}, journal={APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING}, author={Govindaraju, N. and Aleksov, A. and Li, X. and Okuzumi, F. and Wolter, S. D. and Collazo, R. and Prater, J. T. and Sitar, Z.}, year={2006}, month={Nov}, pages={331–335} }
 @article{aleksov_wolter_prater_sitar_2005, title={Fabrication and thermal evaluation of silicon on diamond wafers}, volume={34}, ISSN={["0361-5235"]}, DOI={10.1007/s11664-005-0100-y}, number={7}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Aleksov, A and Wolter, SD and Prater, JT and Sitar, Z}, year={2005}, month={Jul}, pages={1089–1094} }
 @article{aleksov_li_govindaraju_gobien_wolter_prater_sitar_2005, title={Silicon-on-diamond: An advanced silicon-on-insulator technology}, volume={14}, ISSN={["1879-0062"]}, DOI={10.1016/j.diamond.2005.01.019}, abstractNote={Silicon-on-diamond (SOD) technology is proposed as an advanced alternative to conventional silicon-on-insulator (SOI) technology. In SOD, the electrical insulator is diamond, the best thermal conductor in nature. In our SOD concept, the diamond film is highly oriented (HOD), 75–100 μm thick and serves as an electrical insulator, heat spreader and substrate. In this paper, we focus on the thermal evaluation of SOD with a Si device layer on the nucleation side of the diamond film. The obtained results indicated that SOD can sustain up to 10-times higher power loads than SOI. The results were experimentally obtained by R(T) measurements of micro-heaters deposited on the Si device layer and by thermal imaging. 3D finite element thermal simulations using ANSYS confirmed that these numbers are in good agreement with expectations.}, number={3-7}, journal={DIAMOND AND RELATED MATERIALS}, author={Aleksov, A and Li, X and Govindaraju, N and Gobien, JM and Wolter, SD and Prater, JT and Sitar, Z}, year={2005}, pages={308–313} }
 @article{wolter_borca-tasciuc_chen_prater_sitar_2004, title={Processing and thermal properties of highly oriented diamond thin films}, volume={469}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2004.08.062}, abstractNote={This paper discusses early research surrounding bias-enhanced nucleation (BEN) of diamond, which ultimately led to its development as a heteroepitaxial nucleation process. Substrate effects on bias-enhanced nucleation were observed in these early studies, indicating that carbide formers were effective substrates. Later, epitaxial nucleation on (100) β-SiC, (100) Si, and (111) TiC was demonstrated. The thermal attributes of epitaxially textured films have been more recently evaluated by comparing the in-plane thermal conductivity of highly oriented films to those of randomly fiber-textured films. The thermal properties were determined using Joule heating thermometry and indicated room temperature thermal conductivity values of ∼650 and ∼335 W/m K for the respective films. This two-fold improvement is ascribed to reduced phonon scattering at the low angle grain boundaries characterizing the epitaxially textured films. This is further supported by temperature-dependent measurements, which showed a more pronounced sensitivity to these defects within the random fiber-textured films at low measurement temperatures.}, journal={THIN SOLID FILMS}, author={Wolter, SD and Borca-Tasciuc, D and Chen, G and Prater, JT and Sitar, Z}, year={2004}, month={Dec}, pages={105–111} }
 @article{yushin_aleksov_wolter_okuzumi_prater_sitar_2004, title={Wafer bonding of highly oriented diamond to silicon}, volume={13}, ISSN={["1879-0062"]}, DOI={10.1016/j.diamond.2004.04.007}, abstractNote={Polished, highly oriented diamond (HOD) with an RMS roughness of less than 3 nm was bonded to single-side polished silicon wafers in ultra-high vacuum (UHV) at 32 MPa of applied uniaxial pressure. Successful fusion of HOD to silicon was achieved at temperatures above 850 °C. Fusion resulted in the formation of an abrupt interface between the wafers in the areas away from diamond grain boundaries. Voids, partially filled with amorphous material, were observed at the fused interface near the diamond grain boundaries. Preferential diamond polishing, potential out-diffusion of hydrogen from diamond and oxygen from silicon are believed to have contributed to the observed non-uniformity of the bonded interface.}, number={10}, journal={DIAMOND AND RELATED MATERIALS}, author={Yushin, GN and Aleksov, A and Wolter, SD and Okuzumi, F and Prater, JT and Sitar, Z}, year={2004}, month={Oct}, pages={1816–1821} }
 @article{wolter_okuzumi_prater_sitar_2003, title={Bias frequency, waveform and duty-cycle effects on the bias-enhanced nucleation of epitaxial diamond}, volume={440}, ISSN={["0040-6090"]}, DOI={10.1016/S0040-6090(03)00827-7}, abstractNote={In contrast to conventional DC bias-enhanced nucleation, a pre-carburization step was not needed in the processing of epitaxial diamond on (1 0 0) silicon using pulsed biasing. Otherwise, the procedure showed little frequency dependence on the epitaxial process in the range of 1 Hz–2 kHz, resulting in a constant percentage of highly oriented diamond of nearly 50%. The only variation with frequency was a linear increase in the bias current and a corresponding decrease in the biasing time required to form a quasi-continuous nucleation layer. In contrast, the variation of a 60-Hz square waveform duty cycle from 3 to 75% showed a decreasing hyperbolic relationship with the percentage of oriented diamond, with a plateau of ∼45% occurring at duty cycles of ⩽17%. The bias time to film formation was also determined to be inversely proportional to the duty cycle. The collective data highlights the relevance of the waveform attributes on the epitaxial nucleation of diamond on (1 0 0) silicon.}, number={1-2}, journal={THIN SOLID FILMS}, author={Wolter, SD and Okuzumi, F and Prater, JT and Sitar, Z}, year={2003}, month={Sep}, pages={145–151} }
 @article{wolter_yushin_prater_sitar_2003, title={Processing routes for direct bonding of silicon to epitaxially textured diamond}, volume={12}, ISSN={["0925-9635"]}, DOI={10.1016/S0925-9635(02)00392-8}, abstractNote={Direct bonding of (1 0 0) silicon to epitaxially textured diamond is reported. Fusion of the silicon wafers to the diamond specimens was conducted at high temperature, under an applied stress of 32 MPa in a dedicated ultra-high vacuum bonding apparatus. The highly oriented films were characterized by a RMS surface roughness of ∼150.0 nm (via atomic force microscopy) and discrete crystallites that had formed on the otherwise smooth, (1 0 0)-sheet textured surfaces. Consequently, only partial bonding was observed from 950 to 1150 °C; attempts at silicon-to-diamond fusion at lower temperatures were unsuccessful. The diamond films were also mechanically polished to a RMS surface roughness of ∼5.0 nm. Successful bonding of silicon to these films was observed at fusion temperatures ⩾850 °C using the same processing conditions implemented in the unpolished diamond work. Scanning acoustic microscopy revealed a more uniform interface in these silicon-on-diamond specimens.}, number={3-7}, journal={DIAMOND AND RELATED MATERIALS}, author={Wolter, SD and Yushin, GN and Prater, JT and Sitar, Z}, year={2003}, pages={257–261} }
 @article{wolter_borca-tasciuc_chen_govindaraju_collazo_okuzumi_prater_sitar_2003, title={Thermal conductivity of epitaxially textured diamond films}, volume={12}, ISSN={["0925-9635"]}, DOI={10.1016/S0925-9635(02)00248-0}, abstractNote={The in-plane thermal conductivity of epitaxially textured, (1 0 0) diamond has been evaluated in comparison to (1 0 0) diamond possessing a random fiber texture. The diamond films were bias-enhanced nucleated using an alternating current source and grown on (1 0 0) silicon using microwave plasma chemical vapor deposition. Thermal conductivity values of ∼1120 (±11%) W/m K and ∼550 (±11%) W/m K were determined for the epitaxial versus non-epitaxial diamond, respectively, using Joule heating thermometry. This twofold improvement in the thermal conductivity of the epitaxially textured diamond is ascribed to a reduction in the grain boundary defects within the film.}, number={1}, journal={DIAMOND AND RELATED MATERIALS}, author={Wolter, SD and Borca-Tasciuc, DA and Chen, G and Govindaraju, N and Collazo, R and Okuzumi, F and Prater, JT and Sitar, Z}, year={2003}, month={Jan}, pages={61–64} }
 @article{wolter_okuzumi_prater_sitar_2002, title={AC vs. DC bias-enhanced nucleation of highly oriented diamond on silicon (100)}, volume={149}, ISSN={["0013-4651"]}, DOI={10.1149/1.1430720}, abstractNote={Bias-enhanced nucleation of highly oriented diamond on silicon (100) has been investigated in the context of bias type. The formation of aligned crystallites using conventional de substrate biasing was facilitated by a preceding carburization. The optimum biasing conditions following a 1 h carburization involved a bias voltage of -250 V and a stringent bias duration of 3-4 min which produced total nucleation densities of ∼1 × 10 10 cm -2 and highly oriented diamond percentages of -50%. In comparison, the application of a 55-65 min ac substrate bias of 175 V rms (±250 V peak-to-peak ) resulted in a comparable percentage of oriented crystallites and similar crystallographic alignment. However, in this approach a precarburization was not found to be beneficial. This simplification in the processing of the oriented diamond was further aided by a broader bias duration window for producing the optimum combination of high total nucleation density and highly oriented diamond percentage.}, number={2}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Wolter, SD and Okuzumi, F and Prater, JT and Sitar, Z}, year={2002}, month={Feb}, pages={G114–G117} }
 @article{wolter_yushin_okuzumi_stoner_prater_sitar_2002, title={Direct fusion bonding of silicon to polycrystalline diamond}, volume={11}, ISSN={["0925-9635"]}, DOI={10.1016/S0925-9635(01)00608-2}, abstractNote={High temperature fusion of silicon to diamond is reported. Polished, randomly oriented diamond films and unpolished (100) highly oriented diamond films were bonded to single-side polished (100) silicon in a dedicated ultrahigh vacuum bonding apparatus. Direct bonding under an applied uniaxial stress of ∼32 MPa was observed at temperatures above 950 °C. The bonded interface was examined by scanning acoustic microscopy revealing only partial bonding at fusion temperatures of 950 and 1050 °C. In contrast, complete bonding was evidenced at 1150 and 1200 °C, although cracking of the diamond films became more prominent at these higher fusion temperatures.}, number={3-6}, journal={DIAMOND AND RELATED MATERIALS}, author={Wolter, SD and Yushin, GN and Okuzumi, F and Stoner, BR and Prater, JT and Sitar, Z}, year={2002}, pages={482–486} }
 @article{shin_arkun_thomson_miraglia_preble_schlesser_wolter_sitar_davis_2002, title={Growth and decomposition of bulk GaN: role of the ammonia/nitrogen ratio}, volume={236}, ISSN={["0022-0248"]}, DOI={10.1016/S0022-0248(02)00825-4}, abstractNote={Gallium nitride crystals grown via vapor-phase transport processes that incorporate ammonia as the only source of nitrogen below atmospheric pressures experience significant surface roughening and the eventual cessation of growth. Investigations of these phenomena in this research, and in the context of the discovery of a non-ceasing process route to larger GaN crystals, showed that the RMS values of the surface roughness of single crystal GaN (0 0 0 1) films exposed to pure ammonia flowing at 60 sccm for 2 h at 1130°C increased from the as-received value of 3.7–6.8 nm, 21.4 and 32.6 nm at 100, 430 and 760 Torr, respectively. Quadrupole mass spectrometry revealed that the concentrations of H2 and N2 measurably increased at pressures above 400 Torr. The primary reason for the increased roughness above 430 Torr was the enhanced etching of GaN via reaction with atomic and molecular hydrogen derived from the dissociation of the ammonia. At lower pressures, the decomposition of the GaN via the formation and evaporation of N2 and Ga increased in importance relative to etching for enhancing surface roughness. Dilution with nitrogen reduced the amount of hydrogen generated from the dissociation of the ammonia. The GaN surface annealed at 1130°C and 430 Torr in ammonia diluted with 33 vol% N2 maintained the smoothest surface with a nominal RMS value of 10.4 nm. Mixtures with higher and lower percentages of N2 showed enhanced roughness under the same conditions. Use of this optimum gas mixture also allowed the seeded growth of a 1.5×1.5×2.0 mm3 GaN crystal and a 2.3×1.8×0.3 mm3 thick platelet with neither observable decomposition nor cessation of the growth over periods of 36 and 48 h, respectively.}, number={4}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Shin, H and Arkun, E and Thomson, DB and Miraglia, P and Preble, E and Schlesser, R and Wolter, S and Sitar, Z and Davis, RF}, year={2002}, month={Mar}, pages={529–537} }
 @article{yushin_wolter_kvit_collazo_stoner_prater_sitar_2002, title={Study of fusion bonding of diamond to silicon for silicon-on-diamond technology}, volume={81}, ISSN={["0003-6951"]}, DOI={10.1063/1.1516636}, abstractNote={Diamond films grown on silicon were polished to a root-mean-square roughness of 15 nm and bonded to (100) silicon in a dedicated ultrahigh vacuum bonding chamber. Successful bonding was observed at temperatures as low as 950 °C under a uniaxial mechanical stress of 32 MPa. Scanning acoustic microscopy indicated complete bonding at fusion temperatures above 1150 °C, and some cracking of the diamond film. Cross section transmission electron microscopy of the same specimens revealed an intermediate layer consisting of silicon, carbon, and oxygen. This layer was approximately 30 nm thick and had an amorphous structure.}, number={17}, journal={APPLIED PHYSICS LETTERS}, author={Yushin, GN and Wolter, SD and Kvit, AV and Collazo, R and Stoner, BR and Prater, JT and Sitar, Z}, year={2002}, month={Oct}, pages={3275–3277} }
 @article{wolter_okuzumi_prater_sitar_2001, title={Frequency and duty cycle dependence on the pulsed bias-enhanced nucleation of highly oriented diamond on (100) silicon}, volume={186}, ISSN={["0031-8965"]}, DOI={10.1002/1521-396x(200108)186:2<331::aid-pssa331>3.0.co;2-1}, abstractNote={Pulsed bias-enhanced nucleation of highly oriented diamond on (100) silicon is reported. A square waveform substrate bias was implemented in this investigation employing a pulse ON bias voltage of -250 V and a pulse OFF bias voltage of 0 V. An evaluation of the pulse ON fractions of 0.17 and 0.50 revealed a duty cycle dependence on the bias time required for forming a diamond film as well as the highly oriented diamond percentage. Oriented crystallite percentages of nearly 50% and 20% were observed for the 0.17 and 0.50 pulse ON fractions, respectively. Pulse biasing from 10 to 100 Hz (again implementing a square waveform bias and a pulse ON fraction of 0.17) did not influence the process of forming the epitaxial diamond. Throughout this frequency range the onset of diamond film formation was approximately 60 min and a nominal highly oriented diamond percentage of 50% was observed.}, number={2}, journal={PHYSICA STATUS SOLIDI A-APPLIED RESEARCH}, author={Wolter, SD and Okuzumi, F and Prater, JT and Sitar, Z}, year={2001}, month={Jul}, pages={331–337} }
 @article{wolter_prater_sitar_2001, title={Raman spectroscopic characterization of diamond films grown in a low-pressure flat flame}, volume={226}, ISSN={["1873-5002"]}, DOI={10.1016/S0022-0248(01)01274-X}, abstractNote={Diamond films produced in the low-pressure flat flame have been examined using Raman spectroscopy. The effect of the oxy-acetylene gas mixture (R=O2/C2H2 gas ratio of 0.95 to 1.06) and substrate temperature (650–850°C) on the form of the non-diamond carbon as well as the diamond phase purity and crystallinity are reported. An assessment of the diamond crystallinity was achieved by inspection of the full-width-at-half-maximum (FWHM) of the Raman line observed at 1332±0.5 cm−1 representing sp3-bonded carbon. This analysis revealed a FWHM as low as ∼4.3 cm−1 for the optimum growth conditions of an R=1.05 and substrate temperatures of 650–750°C. The broad non-diamond carbon component in the 1350 cm−1 to 1650 cm−1 range was deconvoluted into three distinct Gaussian peaks at 1355±1.5 cm−1, 1470±7.5 cm−1, and 1550±4.0 cm−1. These peaks remained in the same relative proportion regardless of the processing conditions, and the total area of the non-diamond peaks was found to correspond linearly with the background luminescence. A relative comparison of the diamond and non-diamond carbon was used to qualitatively estimate the diamond film phase purity.}, number={1}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Wolter, SD and Prater, JT and Sitar, Z}, year={2001}, month={Jun}, pages={88–94} }
 @misc{liu_wolter_mcclure_stoner_glass_hren_1996, title={Method for forming a diamond coated field emitter and device produced thereby}, volume={5,580,380}, number={1996 Dec. 3}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Liu, J. and Wolter, S. and McClure, M. T. and Stoner, B. R. and Glass, J. T. and Hren, J. J.}, year={1996} }
 @article{wolter_stoner_glass_ellis_buhaenko_jenkins_southworth_1993, title={Textured growth of diamond on silicon via insitu carburization and bias-enhanced nucleation}, volume={62}, number={11}, journal={Applied Physics Letters}, author={Wolter, S. D. and Stoner, B. R. and Glass, J. T. and Ellis, P. J. and Buhaenko, D. S. and Jenkins, C. E. and Southworth, P.}, year={1993}, pages={1215–1217} }
 @article{stoner_ma_wolter_glass_1992, title={Characterization of bias-enhanced nucleation of diamond on silicon by invacuo surface-analysis and transmission electron-microscopy}, volume={45}, number={19}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Stoner, B. R. and Ma, G. H. M. and Wolter, S. D. and Glass, J. T.}, year={1992}, pages={11067–11084} }