@article{grenko_reynolds_schlesser_hren_bachmann_sitar_kotula_2004, title={Nanoscale GaN whiskers fabricated by photoelectrochemical etching}, volume={96}, ISSN={["0021-8979"]}, DOI={10.1063/1.1788841}, abstractNote={GaN whiskers with nanoscale dimensions have been fabricated by photoelectrochemical (PEC) etching in dilute H3PO4 electrolyte. Etching in lower concentration H3PO4 electrolyte for 1 h or for a short time of 5 min at a higher concentration results in individual whiskers with a density of ∼2×109cm−2 and diameters to 15nm. It is observed that ∼10% of them have formed nearly perfect hexagonal plates on the top of the whiskers, which appear to evolve into flowerlike features upon extended etching to 12 min. Such hexagonal plates have not been reported previously in the PEC etching of GaN. The presence of a dislocation along the central axis of the needles is clearly demonstrated, and the etch pattern is suggested to be related to the growth mechanism for GaN on sapphire. When etched for times >30min, these whiskers are typically arranged in clusters with a density of 2–5×107cm−2 and have ten or more whiskers contributing to the central top of the cluster.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Grenko, JA and Reynolds, CL and Schlesser, R and Hren, JJ and Bachmann, K and Sitar, Z and Kotula, PG}, year={2004}, month={Nov}, pages={5185–5188} }
 @article{cardelino_moore_cardelino_mccall_frazier_bachmann_2003, title={Semiclassical calculation of reaction rate constants for homolytical dissociation reactions of interest in organometallic vapor-phase epitaxy (OMVPE)}, volume={107}, ISSN={["1089-5639"]}, DOI={10.1021/jp026289j}, abstractNote={A procedure for calculating homolytic dissociation rate constants is reported for modeling organometallic vapor-phase epitaxy (OMVPE) of III−V compounds for all pressure regimes. Reaction rate constants were predicted following a semiclassical approach based on quantum mechanical calculations and transition-state theory. The critical configuration was determined using linear interpolations for the geometry of the intermediate structures, Morse potentials for the intermediate electronic energies, and Hase's relationship for the vibrational frequencies that become annihilated. Low-pressure rate constants were calculated from Rice−Ramsperger−Kassel−Marcus (RRKM) theory following the Troe approach. The calculations were compared with experimental values for the dissociation of one methyl radical from the closed-shell molecules Al(CH3)3, Ga(CH3)3, and In(CH3)3 and the radical molecules Ga(CH3)2 and In(CH3) and for the dissociation of one hydrogen atom from NH3, PH3, and AsH3. A simplified system of reactions f...}, number={19}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Cardelino, BH and Moore, CE and Cardelino, CA and McCall, SD and Frazier, DO and Bachmann, KJ}, year={2003}, month={May}, pages={3708–3718} }
 @article{narayanan_mahajan_bachmann_woods_dietz_2002, title={Antiphase boundaries in GaP layers grown on (001) Si by chemical beam epitaxy}, volume={50}, ISSN={["1359-6454"]}, DOI={10.1016/S1359-6454(01)00408-6}, abstractNote={We have investigated the origin of contrast features observed in coalesced GaP islands, deposited by chemical beam epitaxy on (001) Si, by high resolution transmission electron microscopy and conventional dark field electron microscopy. Our results indicate that these features are antiphase boundaries (APBs) lying on {110} planes. Image simulations have been performed to show that APBs can only be seen under specific defocus conditions in high resolution lattice images. The observed contrast is attributed to the presence of Ga–Ga and P–P wrong bonds at APBs. A model is proposed to show that the coalescence of GaP islands on the same Si terrace may not produce APBs, and the formation of such boundaries may require the presence of monoatomic steps, separating the coalescing islands.}, number={6}, journal={ACTA MATERIALIA}, author={Narayanan, V and Mahajan, S and Bachmann, KJ and Woods, V and Dietz, N}, year={2002}, month={Apr}, pages={1275–1287} }
 @article{narayanan_mahajan_bachmann_woods_dietz_2002, title={Stacking faults and twins in gallium phosphide layers grown on silicon}, volume={82}, ISSN={["0141-8610"]}, DOI={10.1080/01418610110082034}, abstractNote={Abstract The coalescence of GaP islands, grown on Si(001), Si(111), Si(110) and Si(113) surfaces by chemical beam epitaxy, has been investigated by high-resolution transmission electron microscopy. Stacking faults and first-order twins are observed within islands before coalescence and result from stacking errors during growth on the smaller P-terminated {111} facets of GaP islands. Upon island coalescence, complex moire fringes are observed contiguous to highly faulted {111} planes within epitaxial layers grown on all four Si substrate orientations and are attributed to multiple twinning. Second-and third-order twins are also observed within (111) and (110) layers and their formation is attributed to successive twinning on differently inclined {111} facets. Amongst the four orientations, coalesced growths on the Si(111) surface are the most defective and this may be caused by a higher density of P-terminated {111} facets on islands grown on the Si(111) surface.}, number={4}, journal={PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES}, author={Narayanan, V and Mahajan, S and Bachmann, KJ and Woods, V and Dietz, N}, year={2002}, month={Mar}, pages={685–698} }
 @article{dimmock_madarasz_dietz_bachmann_2001, title={Theoretical analysis of phase-matched second-harmonic generation and optical parametric oscillation in birefringent semiconductor waveguides}, volume={40}, ISSN={["2155-3165"]}, DOI={10.1364/AO.40.001438}, abstractNote={We analyze the phase-matching conditions for second-harmonic generation (SHG) and optical parametric oscillation (OPO) in birefringent nonlinear semiconductor waveguides and apply these results to the model system of ZnGeP2 on a GaP substrate. The analyses and numerical results show that phase matching can be achieved for OPO and SHG for reasonable guide thicknesses throughout much of the infrared, indicating significant potential applications for nonlinear birefringent waveguides. For the fundamental mode of a relatively thick guide the region of phase matching and the phase-matching angles are similar to those in bulk material. However, the waveguide has the added flexibility that phase-matched coupling can occur between the various modes of the guide. For example, the phase-matching region for SHG can be considerably extended by coupling the pump into the guide in the fundamental, m = 0, mode and phase matching to the m = 2 mode of the second harmonic. Significantly, the results indicate, among other things, that ZnGeP2 waveguides with harmonic output in the m = 2 mode can be used for efficient SHG from input radiation in the 9.6-10.6-microm region where bulk efficiencies in this wavelength range are too small to be useful.}, number={9}, journal={APPLIED OPTICS}, author={Dimmock, JO and Madarasz, FL and Dietz, N and Bachmann, KJ}, year={2001}, month={Mar}, pages={1438–1441} }
 @article{cardelino_moore_cardelino_frazier_bachmann_2001, title={Theoretical study of indium compounds of interest for organometallic chemical vapor deposition}, volume={105}, ISSN={["1520-5215"]}, DOI={10.1021/jp0013558}, abstractNote={The structural. electronic and therinochemical properties of indium compounds which are of interest in halide transport and organometallic chemical vapor deposition processes have been studied by ab initio and statistical mechanics methods. The compounds reported include: indium halides and hydrides (InF, InCl, InCl3, InH, InH2, InH3); indium clusters (In2, In3); methylindium, dimethylindium, and their hydrogen derivatives [In(CH3), In(CH3)H, In(CH3)H2, In(CH3)2, In(CH3)2H]; dimethyl-indium dimer [In2(CH3)4], trimethyl-indium [In(CH3)3]; dehydrogenated methyl, dimethyl and trimethylindium [In(CH3)2CH2, In(CH3)CH2, In(CH2)], trimethylindium adducts with ammonia, trimethylamine and hydrazine [(CH3)3In:NH3, (CH3)3In:N(CH3)3, (CH3)3In:N(H2)N(H2)]; dimethylamino-indium and methylimino-indium [In(CH3)2(NH2), In(CH3)(NH)]; indium nitride and indium nitride dimer (InN, In2N2), indium phosphide, arsenide and antimonide ([InP, InAs, InSb). The predicted electronic properties are based on density functional theory calculations; the calculated thermodynamic properties are reported following the format of the JANAF (Joint Army, Navy, NASA, Air Force) Tables. Equilibrium compositions at two temperatures (298 and 1000 K) have been analyzed for groups of competing simultaneous reactions.}, number={5}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Cardelino, BH and Moore, CE and Cardelino, CA and Frazier, DO and Bachmann, KJ}, year={2001}, month={Feb}, pages={849–868} }
 @article{narayanan_mahajan_sukidi_bachmann_woods_dietz_2000, title={Orientation mediated self-assembled gallium phosphide islands grown on silicon}, volume={80}, ISSN={["0141-8610"]}, DOI={10.1080/01418610008212068}, abstractNote={Abstract Evolution of gallium phosphide epitaxial islands, grown on the (001), (111), (110) and (113) surfaces of Si by chemical beam epitaxy, has been investigated by p-polarized reflectance spectroscopy, transmission electron microscopy and atomic force microscopy. The growth nucleates as faceted three-dimensional islands on the (001) and (111) Si surfaces because of the polar nature of the heterointerface which increases the interfacial energy. A more two-dimensional-like growth mode is seen on the (110) and (113) surfaces which is attributed to the absence of charge build up at the GaP—Si heterointerface for these orientations, thereby reducing the interface energy. Islands grown on (001) Si become more faceted and larger in size with increase in growth temperature. This is due to a lower incubation time and enhanced atomic mobility at high temperatures. Wurtzite GaP has been observed to coexist with the zincblende polytype in some of the islands grown on (111) Si at 560°C. Arguments have been developed to rationalize these observations.}, number={3}, journal={PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES}, author={Narayanan, V and Mahajan, S and Sukidi, N and Bachmann, KJ and Woods, V and Dietz, N}, year={2000}, month={Mar}, pages={555–572} }
 @article{madarasz_dimmock_dietz_bachmann_2000, title={Sellmeier parameters for ZnGaP2 and GaP}, volume={87}, ISSN={["0021-8979"]}, DOI={10.1063/1.372050}, abstractNote={Sellmeier parameters are determined for the birefringent material ZnGaP2 and the singly refractive material GaP by the minimization of chi-square employing the Levenberg–Marquardt method. The distinguishing feature of the present work is that all five Sellmeier parameters are treated as adjustable. In previous work the Sellmeier parameter related to the restrahlen frequency was fixed and set equal for both ordinary and extraordinary waves in the birefringent material. The fitted results show there is approximately an 8% difference between the two. Taking this parameter as adjustable allows for a better fit on all other parameters.}, number={3}, journal={JOURNAL OF APPLIED PHYSICS}, author={Madarasz, FL and Dimmock, JO and Dietz, N and Bachmann, KJ}, year={2000}, month={Feb}, pages={1564–1565} }
 @article{madarasz_dimmock_dietz_bachmann_2000, title={Sellmeier parameters for ZnGaP2 and GaP (vol 87, pg 1564, 2000)}, volume={87}, ISSN={["0021-8979"]}, DOI={10.1063/1.373029}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={Madarasz, FL and Dimmock, JO and Dietz, N and Bachmann, KJ}, year={2000}, month={May}, pages={7597–7597} }
 @article{sukidi_bachmann_narayanan_mahajan_1999, title={Initial stages of heteroepitaxy of GaP on selected silicon surfaces}, volume={146}, ISSN={["0013-4651"]}, DOI={10.1149/1.1391736}, abstractNote={In this paper we report recent results regarding the nucleation and growth of GaP on Si(001), (111), and (113) surfaces under the conditions of pulsed chemical beam epitaxy using tertiary butylphosphine and triethylgallium as source vapors. The kinetics of nucleation and island growth were monitored in real-time by p-polarized reflectance (PR) and laser light scattering measurements. These measurements were supplemented by ex situ atomic force microscopy and high-resolution transmission electron microscopy studies. We report on the observation of an incubation time, τ i , which strongly depends on surface orientation with τ i (001) < τ i (111) < τ i (113) and, for a given surface orientation and source vapor flux, decreases with increasing substrate temperature. At time t ≥ τ i autocatalytic steps observed in the PR signal are correlated to nucleation and overgrowth of GaP nuclei. In addition, PR reveals changes during GaP growth which result in the deterioration of the previously formed perfect GaP islands that are in registry with the underlying silicon lattice. The change in growth mode may be associated with the formation of stacking faults on faceted GaP islands.}, number={3}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Sukidi, N and Bachmann, KJ and Narayanan, V and Mahajan, S}, year={1999}, month={Mar}, pages={1147–1150} }
 @article{bachmann_banks_hopfner_kepler_lesure_mccall_scroggs_1999, title={Optimal design of a high pressure organometallic chemical vapor deposition reactor}, volume={29}, ISSN={["0895-7177"]}, DOI={10.1016/S0895-7177(99)00071-0}, abstractNote={A team composed of material scientists, physicists, and applied mathematicians have used computer simulations as a fundamental design tool in developing a new prototype High Pressure Organometallic Chemical Vapor Deposition (HPOMCVD) reactor for use in thin film crystal growth. Early design of the HPOMCVD reactor dramatically evolved long before any physical reactor was built. This effort offers a strong endorsement of such multidisciplinary, computationally based modeling teams in the design of new products in areas of emerging technologies where heretofore extensive and costly experimental design was the central paradigm.}, number={8}, journal={MATHEMATICAL AND COMPUTER MODELLING}, author={Bachmann, KJ and Banks, HT and Hopfner, C and Kepler, GM and LeSure, S and McCall, SD and Scroggs, JS}, year={1999}, month={Apr}, pages={65–80} }
 @article{narayanan_sukidi_bachmann_mahajan_1999, title={Origins of defects in self assembled GaP islands grown on Si(001) and Si(111)}, volume={357}, ISSN={["0040-6090"]}, DOI={10.1016/S0040-6090(99)00474-5}, abstractNote={Microstructures of GaP epitaxial islands grown on Si(001) and Si(111) by chemical beam epitaxy have been investigated by transmission electron microscopy (TEM). Results indicate that planar-defect free GaP islands of sizes <20 nm can be produced at 560°C on Si(001). Some of the islands are faceted on {111} and {113} planes. Subsequent planar defect formation occurs due to stacking errors on the smaller {111} facets of GaP islands that may be P-terminated. These stacking errors are attributed to the low surface mobility on P-terminated facets. A high density of planar defects is observed in smaller islands grown on Si(001) at 420°C, a consequence of reduced atomic mobility at low temperatures that leads to {111} stacking errors. Wurtzite GaP has been observed to coexist with the zinc-blende polytype in some of the islands grown on Si(111) at 560°C.}, number={1}, journal={THIN SOLID FILMS}, author={Narayanan, V and Sukidi, N and Bachmann, KJ and Mahajan, S}, year={1999}, month={Dec}, pages={53–56} }
 @misc{narayanan_sukidi_hu_dietz_bachmann_mahajan_shingubara_1998, title={Growth of gallium phosphide layers by chemical beam epitaxy on oxide patterned (001)silicon substrates}, volume={54}, ISSN={["0921-5107"]}, DOI={10.1016/s0921-5107(98)00169-x}, abstractNote={GaP layers grown by chemical beam epitaxy in [110] channels fabricated on oxide-patterned (001)silicon substrates have been examined in cross-section by conventional and high resolution transmission electron microscopy. Results indicate that the layers are single crystalline. For the imaging conditions used, [110] cross-sectional micrographs show that growths in contact with the oxide exhibit twinning on one edge-on variant, whereas faults or twins are observed on two such variants in the layers which nucleate on the silicon substrate. Arguments for rationalizing these observations are developed, and their implications to improve the quality of the layer by confining faults or twins by the oxide sidewall are discussed.}, number={3}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Narayanan, V and Sukidi, N and Hu, CM and Dietz, N and Bachmann, KJ and Mahajan, S and Shingubara, S}, year={1998}, month={Jun}, pages={207–209} }
 @article{kepler_hopfner_scroggs_bachmann_1998, title={Simulation of a vertical reactor for high pressure organometallic chemical vapor deposition}, volume={57}, ISSN={["0921-5107"]}, DOI={10.1016/s0921-5107(98)00256-6}, abstractNote={The suitability of a vertical cylindrical reactor with highly constrained radial flow from a central gas injection port past a set of heated substrate wafers that are embedded in the top channel wall has been evaluated in the context of organometallic chemical vapor deposition (OMCVD) at elevated pressure. Numerical simulations showed that, in addition to the limitation on the channel height necessary for preventing buoyancy driven recirculation, negotiating the ninety-degree bend at the inlet is problematic and also constrains the channel height below a critical value, at which the radial flow area after the inlet bend is equal to the cross-sectional area of the central gas injection port. Restricting the channel height poses the danger of heating of the channel wall opposite to the substrate wafers causing potential problems with deposition of decomposition products and competitive polycrystalline film growth at this location. These problems can be avoided by actively cooling the channel wall opposite to the substrate and by keeping the retention time of the source vapor molecules and fragments thereof in the wafer location below a critical value.}, number={1}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Kepler, GM and Hopfner, C and Scroggs, JS and Bachmann, KJ}, year={1998}, month={Dec}, pages={9–17} }
 @article{backmann_kepler_1997, title={Heteroepitaxial processes at low and elevated pressures}, volume={3123}, ISBN={["0-8194-2545-1"]}, DOI={10.1117/12.277707}, abstractNote={Based on design criteria established in preceding work for conditions of moderately elevated pressure (less than or equal to 8 bar) we have designed and evaluated a reactor for chemical vapor deposition (CVD) at high pressure (less than or equal to 100 bar). While at moderate pressure non-turbulent unidirectional forced channel flow past a heated substrate wafer can be realized, at high pressure, the flow is expected to become turbulent. Due to phase front distortions and variations in angle of incidence associated with density fluctuations and density gradients in the high pressure vapor phase in the vicinity of the hot substrate -- the precision of methods of real-time optical process monitoring that employ polarized light, such as, p-polarized reflectance spectroscopy (PRS), is degraded. Above a critical pressure, features in the optical signals related to chemical kinetics and to the kinetics of heteroepitaxy, thus are no longer resolved. Therefore, experimentation at reduced gravity, which extends the pressure range of non-turbulent flow, and alternative robust methods of real-time optical process monitoring are considered. At very high pressures, where real-time process monitoring is severely curtailed, CVD processing must rely on predictions of numerical models -- validated by experimentation at lower pressure/low gravity. Experimentation at high pressure is needed to access materials, properties and/or structures that otherwise cannot be realized.}, journal={MATERIALS RESEARCH IN LOW GRAVITY}, author={Backmann, KJ and Kepler, GM}, year={1997}, pages={64–74} }
 @article{bachmann_hopfner_sukidi_miller_harris_aspnes_dietz_tran_beeler_ito_et al._1997, title={Molecular layer epitaxy by real-time optical process monitoring}, volume={112}, DOI={10.1016/S0169-4332(96)00975-0}, abstractNote={In this paper we consider modern methods of optical process monitoring and control in the context of atomic layer epitaxy. One specific method, p-polarized reflectance spectroscopy (PRS), is chosen to assess details of layer-by-layer growth. We show that PRS monitoring under conditions of steady-state growth by pulsed chemical beam epitaxy (PCBE) can achieve the deposition of molecular layers of GaP on silicon (100) deposited with a precision of 5%, which can be improved by reducing the growth rate and increasing the period of time averaging of the reflectance data. Since in the nucleation period prior to formation of a contiguous heteroepitaxial film inhomogeneous surface chemistry and roughening complicates the modeling of the overgrowth process, advances in both experimental methods and theory are required for extending the control to non-steady-state growth conditions. Results of simultaneous single-wavelength PR monitoring and laser light scattering measurements in conjunction with atomic force microscopy studies of short period heteroepitaxial overgrowth processes are presented. The extension of PRS to the monitoring of organometallic chemical vapor deposition at higher pressures is also discussed.}, number={1997 Mar.}, journal={Applied Surface Science}, author={Bachmann, K. J. and Hopfner, C. and Sukidi, N. and Miller, A. E. and Harris, C. J. and Aspnes, D. E. and Dietz, N. A. and Tran, Hien and Beeler, S. C. and Ito, K. and et al.}, year={1997}, pages={38–47} }
 @inproceedings{aspnes_dietz_rossow_bachmann_1997, title={Multilevel approaches toward monitoring and control of semiconductor epitaxy}, DOI={10.1557/proc-448-451}, abstractNote={Various optical techniques have been developed over the last few years to allow real-time analysis of regions of importance for semiconductor epitaxy, in particular the unreacted and reacted parts of the surface reaction layer (SRL) and the near-surface region of the sample. When coupled with emerging microscopic methods of calculating optical properties, these approaches will allow several levels of control beyond that which has been currently demonstrated.}, booktitle={Control of semiconductor surfaces and interfaces: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A. (Materials Research Society Symposium proceedings, no. 448)}, publisher={Pittsburgh, PA: Materials Research Society}, author={Aspnes, D. E. and Dietz, N. and Rossow, U. and Bachmann, K. J.}, year={1997}, pages={451–462} }
 @article{dietz_sukidi_harris_bachmann_1997, title={Real-time monitoring of surface processes by p-polarized reflectance}, volume={15}, ISSN={["0734-2101"]}, DOI={10.1116/1.580712}, abstractNote={Understanding surface chemistry under steady-state epitaxial growth involving organo-metallic chemical precursor molecules is essential for optimizing growth processes. Surface-sensitive optical real-time sensor techniques are very well suited for this task as their applications are not limited to a high vacuum environment. In this article we report the combined application of the optical sensor techniques p-polarized reflectance (PR) and laser light scattering for the real-time monitoring of low temperature growth of epitaxial GaP/GaxIn1−xP heterostructures on Si(001) and GaAs(001) substrates by pulsed chemical beam epitaxy. The high surface sensitivity of PR allows to follow growth processes with submonolayer resolution during the sequential precursor exposure of the surface that causes periodic alterations in composition and thickness of a surface reaction layer (SRL), the effect of which is monitored by PR as a periodic fine structure. This fine structure is superimposed on interference oscillations, ...}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS}, author={Dietz, N and Sukidi, N and Harris, C and Bachmann, KJ}, year={1997}, pages={807–815} }
 @misc{bachmann_dietz_miller_1996, title={Methods for monitoring and controlling deposition and etching using p-polarized reflectance spectroscopy}, volume={5552327}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Bachmann, K. J. and Dietz, N. and Miller, A. E.}, year={1996} }
 @book{bachmann_1995, title={The materials science of microelectronics}, ISBN={0895732807}, publisher={New York: VCH}, author={Bachmann, K. J.}, year={1995} }