@article{aspnes_mantese_bell_rossow_2000, title={Coherence effects and time dependences of the optical response of surfaces and interfaces of optically absorbing materials}, volume={220}, ISSN={["1521-3951"]}, DOI={10.1002/1521-3951(200007)220:1<709::aid-pssb709>3.0.co;2-d}, abstractNote={Components in the optical spectra of surfaces and interfaces that are related to energy and lifetime derivatives of the bulk dielectric response can be understood if final-state coherence effects that are ignored in conventional quasistatic approaches are retained. The theory shows that the finite penetration depth of light in optically absorbing materials generates wave packets that are localized to the same region as the photon field. This eliminates the energy-conservation and causality violations of the conventional picture and in particular allows the surface or interface potential to influence energy gaps and broadening parameters. Since the localized packets are only stable dynamically, optical absorption is an intrinsically nonlocal process. The formulation also provides a quantitative physical basis for Lorentzian broadening, which is usually treated phenomenologically.}, number={1}, journal={PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS}, author={Aspnes, DE and Mantese, L and Bell, KA and Rossow, U}, year={2000}, month={Jul}, pages={709–715} }
 @article{mantese_xue_sakurai_aspnes_1999, title={Analysis of high-index Si(001) surfaces by reflectance difference spectroscopy}, volume={17}, ISSN={["1520-8559"]}, DOI={10.1116/1.581867}, abstractNote={We report surface-induced optical anisotropy spectra of high-index Si(115), (114), and (113) surfaces obtained using reflectance difference spectroscopy. Air-oxidized surfaces show sharp derivative-type features that are step-induced and located near the critical point energies of bulk Si, consistent with those of lower-index Si(001) surfaces. Clean reconstructed surfaces are characterized by a broad feature near 3 eV that tends to decrease in amplitude upon H exposure and a step-induced structure near the (E0′,E1) transition of bulk Si. In contrast, H exposure of Ge-covered surfaces tends to sharpen and enhance lower-energy structures. The derivative-type features located near the bulk critical point energies of Si can be described in terms of electronic states localized by the finite penetration depth of light.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Mantese, L and Xue, QK and Sakurai, T and Aspnes, DE}, year={1999}, pages={1652–1656} }
 @article{rossow_mantese_aspnes_bell_ebert_1999, title={Linear optical properties of Si surfaces and nanostructures}, volume={215}, number={1}, journal={Physica Status Solidi. B, Basic Solid State Physics}, author={Rossow, U. and Mantese, L. and Aspnes, D. E. and Bell, K. A. and Ebert, M.}, year={1999}, pages={725–729} }
 @article{mantese_bell_aspnes_rossow_1999, title={Photon-induced localization in optically absorbing materials}, volume={253}, ISSN={["0375-9601"]}, DOI={10.1016/S0375-9601(98)00953-0}, abstractNote={We show that components of surface- and interface-related optical spectra that are related to derivatives of their bulk dielectric functions are due to a dynamic photon-induced localization of the initial and final states. Localization is described by correlation effects that arise from the finite penetration depth of light in optically absorbing materials, and lead to a substantially different perspective of optical absorption than that given by conventional theory.}, number={1-2}, journal={PHYSICS LETTERS A}, author={Mantese, L and Bell, KA and Aspnes, DE and Rossow, U}, year={1999}, month={Mar}, pages={93–97} }
 @article{mantese_bell_rossow_aspnes_1998, title={Interpretation of critical point energy shifts in crystalline Si by near-surface localization of excited electronic states}, volume={313}, ISSN={["0040-6090"]}, DOI={10.1016/S0040-6090(97)00883-3}, abstractNote={Various surface-optical spectra can be described in terms of energy derivatives of the bulk dielectric function. The spectra unequivocally indicate that critical point energies obtained from optical data are not necessarily equal to bulk values and that surface chemical and structural terminations are at least contributing factors. We invoke localization and transition-lifetime arguments to describe these effects. Existing surface-optical calculations do not address these contributions, which may explain in part why discrepancies remain between theory and experiment.}, number={1998 Feb.}, journal={THIN SOLID FILMS}, author={Mantese, L and Bell, KA and Rossow, U and Aspnes, DE}, year={1998}, month={Feb}, pages={557–560} }
 @article{rossow_mantese_aspnes_1998, title={Lineshapes of surface induced optical anisotropy spectra measured by RDS/RAS}, volume={123}, ISSN={["0169-4332"]}, DOI={10.1016/S0169-4332(97)00544-8}, abstractNote={In this paper we discuss lineshapes of reflectance-difference spectroscopy (RDS/RAS) spectra of various surfaces. This work aims toward a basic understanding of the surface optical response. We find that in some cases RDS spectra are given by the bulk dielectric function or its energy derivative. In the former case screening effects such as the surface local field effect are dominant. In the latter case the surface modifies the bulk electronic structures and we find that the excited states must be localized near the surface. Even in the simplest case where the anisotropy originates at the surface the optical anisotropy in general depends on the dielectric function of the bulk as well as that of the surface.}, number={1998 Jan.}, journal={APPLIED SURFACE SCIENCE}, author={Rossow, U and Mantese, L and Aspnes, DE}, year={1998}, month={Jan}, pages={237–242} }
 @article{aspnes_mantese_bell_rossow_1998, title={Many-body and correlation effects in surface and interface spectra of optically absorbing materials}, volume={170}, number={2}, journal={Physica Status Solidi. A, Applications and Materials Science}, author={Aspnes, D. E. and Mantese, L. and Bell, K. A. and Rossow, U.}, year={1998}, pages={199–210} }
 @article{aspnes_mantese_bell_rossow_1998, title={Photon-induced localization and final-state correlation effects in optically absorbing materials}, volume={16}, ISSN={["1071-1023"]}, DOI={10.1116/1.590176}, abstractNote={Two consequences of the absorption of light in optically absorbing materials that appear not to have been recognized previously are: (1) localization of the final electron and hole states involved in the absorption process into wave packets and (2) propagation of these wave packets with their respective group velocities. We demonstrate the existence of these phenomena by applying first-order time-dependent perturbation theory to a simple model that can be solved analytically even when correlations that are ordinarily discarded in the random phase approximation are retained. This approach provides a natural explanation of components in surface- and interface-optical spectra that are related to energy derivatives of the bulk dielectric function εb and apparent differences in nominally bulk critical point energies Eg and broadening parameters Γ depending on surface conditions.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Aspnes, DE and Mantese, L and Bell, KA and Rossow, U}, year={1998}, pages={2367–2372} }
 @article{bell_mantese_rossow_aspnes_1998, title={Systematic differences among nominal reference dielectric function spectra for crystalline Si as determined by spectroscopic ellipsometry}, volume={313}, ISSN={["0040-6090"]}, DOI={10.1016/S0040-6090(97)00804-3}, abstractNote={Results of the first systematic investigation of differences among reference-quality ellipsometrically measured pseudodielectric function 〈ε〉 spectra of crystalline Si are discussed. These data are nominally used to approximate the bulk dielectric function of this material for optical modeling. In addition to the expected influence of residual overlayers, we identify surface-local-field and energy-derivative effects even between spectra obtained for seemingly identical H-terminated surfaces. Model calculations indicate that these effects account for nearly all differences among spectra studied. The isotropic contribution to the surface-local-field effect is also reported.}, number={1998 Feb.}, journal={THIN SOLID FILMS}, author={Bell, KA and Mantese, L and Rossow, U and Aspnes, DE}, year={1998}, month={Feb}, pages={161–166} }
 @article{mantese_bell_rossow_aspnes_1997, title={Evidence of near-surface localization of excited electronic states in crystalline Si}, volume={15}, ISSN={["2166-2746"]}, DOI={10.1116/1.589438}, abstractNote={Surface- and interface-related spectra, obtained either directly by techniques such as reflectance-difference (-anisotropy) spectroscopy or indirectly by subtracting pseudodielectric function spectra obtained ellipsometrically on surfaces with different chemical termination, exhibit features related to energy derivatives of the bulk dielectric function. We argue that these spectra provide direct evidence that the excitations involved are localized both in space and time. These data unequivocally indicate that critical point energies obtained from above-band-gap ellipsometric or reflectrometric optical spectra are not necessarily equal to bulk values, and that surface chemical and structural termination is at least one contributing factor. Present surface-optical calculations do not include these effects, which may explain, in part, remaining discrepancies between theory and experiment.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Mantese, L and Bell, KA and Rossow, U and Aspnes, DE}, year={1997}, pages={1196–1200} }
 @article{bell_mantese_rossow_aspnes_1997, title={Surface and interface effects on ellipsometric spectra of crystalline Si}, volume={15}, DOI={10.1116/1.589440}, abstractNote={We present the first systematic investigation of the differences among reference-quality ellipsometrically measured pseudodielectric function 〈ε〉 spectra of crystalline Si, which are nominally used to approximate the bulk dielectric function of this material. In addition to the expected influence of residual overlayers, we identify surface-local-field and energy-derivative effects, the latter representing shifts between bulk and measured critical point energies, as well as changes in excited-carrier lifetimes due to the surface. Model calculations indicate that these four effects account for nearly all differences among spectra studied, although a second-energy-derivative component appears at the E1 transition in some cases. The isotropic contribution to the surface-local-field effect is observed for the first time.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Bell, KA and Mantese, L and Rossow, U and Aspnes, DE}, year={1997}, pages={1205–1211} }