@article{gokce_gundogdu_adles_aspnes_2011, title={Back-reflection Second-harmonic Generation of (111)Si: Theory and Experiment}, volume={58}, ISSN={["1976-8524"]}, DOI={10.3938/jkps.58.1237}, abstractNote={We consider second-harmonic generation (SHG) from a (111) surface of a tetrahedrally bonded semiconductor illuminated at normal incidence by a focused pump beam of Gaussian cross section as a model of SHG by focused beams. Calculations are done in the anisotropic bond model (ABM) and the results are applied to Si. The unit-cell configuration is simple enough for the calculations to be done analytically, so the results can be compared directly to similar calculations done for amorphous material. Although the differences in unit-cell symmetry occur on the atomic scale, they lead to large differences in the spatial distribution of the emerging radiation. Lateral focusing, which might be expected to increase the bulk contribution to SHG by increasing the lateral field gradient, has little effect; the spatial-dispersion contribution remains dominated by the phase term. Focusing does not inhibit backscattered SHG from the bulk, although our data on the oxidation of H-terminated (111)Si clearly show that in some cases the interface contribution dominates by a wide margin.}, number={5}, journal={JOURNAL OF THE KOREAN PHYSICAL SOCIETY}, author={Gokce, B. and Gundogdu, K. and Adles, E. J. and Aspnes, D. E.}, year={2011}, month={May}, pages={1237–1243} }
@article{adles_2011, title={Developing an epitaxial growth process for ZnO by MOCVD using real-time spectroscopic ellipsometry}, volume={519}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2010.12.071}, abstractNote={Real-time diagnostics are an essential tool in the development and improvement of growth processes for new materials. Here we use real-time spectroscopic polarimetric observations of zinc oxide deposition, and a chemical model derived therefrom, to develop a method of growing dense, two-dimensional zinc oxide epitaxially on sapphire by metalorganic chemical vapor deposition. With the transition between deposition and etching being 13% in the diethylzinc flow rate, it is unlikely that we would have discovered this process without the use of real-time spectroscopic ellipsometry. New photoluminescence data support our conclusion that using this cyclical growth process yields improved material.}, number={9}, journal={THIN SOLID FILMS}, author={Adles, E. J.}, year={2011}, month={Feb}, pages={2674–2677} }
@article{gokce_adles_aspnes_gundogdu_2011, title={Measurement and Control of In-Plane Surface Chemistry During Oxidation of H-Terminated (111)Si}, volume={1399}, ISSN={["0094-243X"]}, DOI={10.1063/1.3666321}, abstractNote={We demonstrate both directional control and measurement of the oxidation of H‐terminated (111)Si. Control is achieved through externally applied strain, with strained back bonds oxidizing faster than unstrained ones. Real‐time measurement is achieved by second‐harmonic generation (SHG), with SHG anisotropy data analyzed with the anisotropic bond‐charge model of nonlinear optics. Anisotropic oxidation also results in structural changes, which appear as rotations of the average orientations of the back bonds from their unperturbed directions.}, journal={PHYSICS OF SEMICONDUCTORS: 30TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS}, author={Gokce, Bilal and Adles, Eric J. and Aspnes, David E. and Gundogdu, Kenan}, year={2011} }
@article{adles_aspnes_2010, title={Chemical-etch-assisted growth of epitaxial zinc oxide}, volume={28}, ISSN={["0734-2101"]}, DOI={10.1116/1.3305814}, abstractNote={The authors use real-time spectroscopic polarimetric observations of growth, and a chemical model derived therefrom, to develop a method of growing dense, two-dimensional zinc oxide epitaxially on sapphire by metal organic chemical vapor deposition. Particulate zinc oxide formed in the gas phase is used to advantage as the deposition source. Their real-time data provide unequivocal evidence that a seed layer is required, unwanted fractions of ZnO are deposited, but these fractions can be removed by cycling between brief periods of net deposition and etching. The transition between deposition and etching occurs with zinc precursor concentrations that only differ by 13%. These processes are understood by considering the chemistry involved.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Adles, E. J. and Aspnes, D. E.}, year={2010}, pages={689–692} }
@article{adles_aspnes_2008, title={Application of the anisotropic bond model to second-harmonic generation from amorphous media}, volume={77}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.77.165102}, abstractNote={As a step toward analyzing second-harmonic generation SHG from crystalline Si nanospheres in glass, we develop an anisotropic bond model ABM that expresses SHG in terms of physically meaningful parameters and provide a detailed understanding of the basic physics of SHG on the atomic scale. Nonlinear-optical NLO responses are calculated classically via the four fundamental steps of optics: evaluate the local field at a given bond site, solve the force equation for the acceleration of the charge, calculate the resulting radiation, then superpose the radiation from all charges. Because the emerging NLO signals are orders of magnitude weaker and occur at wavelengths different from that of the pump beam, these steps are independent. Paradoxically, the treatment of NLO is therefore simpler than that of linear optics LO, where these calculations must be done self-consistently. The ABM goes beyond previous bond models by including the complete set of underlying contributions: retardation RD, spatial-dispersion SD, and magnetic MG effects, in addition to the anharmonic restoring force acting on the bond charge. Transverse as well as longitudinal motion is also considered. We apply the ABM to obtain analytic expressions for SHG from amorphous materials under Gaussian-beam excitation. These materials represent an interesting test case not only because they are ubiquitous but also because the anharmonic-force contribution that dominates the SHG response of crystalline materials and ordered interfaces vanishes by symmetry. The remaining contributions, and hence the SHG signals, are entirely functions of the LO response and beam geometry, so the only new information available is the anisotropy of the LO response at the bond level. The RD, SD, and MG contributions are all of the same order of magnitude, so none can be ignored. Diffraction is important in determining not only the pattern of the emerging beam but also the phases and amplitudes of the different terms. The plane-wave expansion that gives rise to electric quadrupole magnetic dipole effects in LO appears here as retardation. Using the paraxial-ray approximation, we reduce the results to the isotropic case in two limits, that where the linear restoring force dominates glasses and that where it is absent metals. Both forward- and backscattering geometries are discussed. Estimated signal strengths and conversion efficiencies for fused silica appear to be in general agreement with data where available. Predictions that allow additional critical tests of these results are made.}, number={16}, journal={PHYSICAL REVIEW B}, author={Adles, E. J. and Aspnes, D. E.}, year={2008}, month={Apr} }
@article{adles_aspnes_2008, title={The anisotropic bond model of nonlinear optics}, volume={205}, ISSN={1862-6300 1862-6319}, url={http://dx.doi.org/10.1002/pssa.200777846}, DOI={10.1002/pssa.200777846}, abstractNote={The anisotropic‐bond model (ABM) of nonlinear optics (NLO) provides a simple means of calculating NLO properties of materials by factoring the problem into four parts: first, determination of the local field at a bond‐charge site; second, solution of the anharmonic force equation of the bond charge; third, calculation of the radiation from the charge; and fourth, superposition of the radiation from all charges. Because this factorization is impossible in linear optics, this is one of the few cases where a nonlinear problem is simpler than its linear equivalent. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)}, number={4}, journal={physica status solidi (a)}, publisher={Wiley}, author={Adles, E. J. and Aspnes, D. E.}, year={2008}, month={Apr}, pages={728–731} }
@misc{simunovic_swartzel_adles_2007, title={Method and system for conservative evaluation, validation and monitoring of thermal processing}, volume={7,213,967}, number={2007 May 8}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Simunovic, J. and Swartzel, K. R. and Adles, E.}, year={2007} }
@misc{simunovic_swartzel_adles_2006, title={Method and system for conservative evaluation, validation and monitoring of thermal processing}, volume={7,004,620}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Simunovic, J. and Swartzel, K. R. and Adles, E.}, year={2006} }
@article{peng_adles_wang_aspnes_2005, title={Relative bulk and interface contributions to optical second-harmonic generation in silicon}, volume={72}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.72.205203}, abstractNote={Using the simplified bond-hyperpolarizability model, we obtain analytic expressions for the first-forbidden spatial dispersion, magnetic dipole/electric quadrupole bulk contributions to second-harmonic generation for centrosymmetric materials. Applying these to oxidized Si, we show theoretically and by comparison to experiment that the relative bulk contribution near 800 nm is minor, less than half that of the interface, but that the coherent superposition of bulk and interface contributions is important and cannot be neglected.}, number={20}, journal={PHYSICAL REVIEW B}, author={Peng, HJ and Adles, EJ and Wang, JFT and Aspnes, DE}, year={2005}, month={Nov} }
@misc{simunovic_swartzel_adles_2004, title={Method and system for conservative evaluation, validation and monitoring of thermal processing}, volume={6,776,523}, number={2004 Aug. 17}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Simunovic, J. and Swartzel, K. R. and Adles, E.}, year={2004} }