Determination of the optical properties of amorphous selenium films by a classical damped oscillator model

Abstract

Amorphous selenium films were produced by vacuum evaporation onto glass and aluminum substrates. The chemical composition of the films and interfaces were studied using scanning Auger electron spectroscopy. To gain some insight into the optical properties of the selenium films, we used the classical oscillator model to fit the transmittance spectrum.

Determination of Optical Properties of Undoped Amorphous Selenium (a-Se) Films by Dielectric Modeling of Their Normal-Incidence Transmittance Spectra

“…Therefore, in principle, two independent optical measurements are necessary at each spectral wavelength to solve for the unknowns and but, in practice, the true geometric thickness of the film is not known in prior and is thus to be determined at the same time-that is, three unknowns to be retrieved from two independent optical measurements at the same spectral wavelength, which demands adequate model suppositions or an otherwise optical analytical approach (Tan, 2006;Tan et al, 2007;Tan et al, 2006;Vautier et al, 1988;Bettstelleret al, 1993;Mulama et al, 2014;Benkhedir, 2006;Solieman et al, 2014;Adachi & Kao1980;Kotkata & Abdel-Wahab, 1990;Kotkata et al, 2009;Navarrete et al, 1990;Solieman & Abu-Sehly, 2010;Nagels et al, 1995;Tichy et al, 1996;Nagels et al, 1997;Tauc, 1972;Tauc, 1979;Heavens, 1991;Azzam & Bashara, 1987;Ward, 1994;Dragoman & Dragoman, 2002;Stenzel, 2005;Joo et al, 1999;Dobrowolski et al, 1983;Klein et al, 1990;Kukinyi et al, 1996;Chiao et al, 1995;Case, 1983;Peng & Desu, 1994;Birgin et al, 1999;Mulato et al, 2000;Erarslan & Gungor, 2010;Ventura et al, 2005;Manifacier et al, 1976;Swanepoel, 1983;Minkov, 1990;El-Naggar et al, 2009;…”

“…A common approach is the indirect (inverse) synthesis technique { , }⟶{ , }, which is based on inserting multi-constant dispersion function for and (Tan, 2006;Tan et al, 2007;Tan et al, 2006;Theiss, 2012;Forouhi & Bloomer, 1986;Forouhi & Bloomer, 1988;Adachi, 1991;Jellison & Modine, 1996;Chambouleyron & Martínez, 2001;Truong & Tanemura, 2006;Kasap & Capper, 2006;Christman, 1988;Rogalski & Palmer, 2000;Palik, 1998;Dressel & Grüner, 2002;Reitz et al, 1993) into theoretical formulas of transmittance and/or reflectance of a multi-layered structure including the film, and then use a powerful statistical curve-fitting program to attain simulated transmittance and reflectance curves to the entire and data (Solieman et al, 2014;Navarrete et al, 1990;Solieman & Abu-Sehly, 2010;Joo et al, 1999;Dobrowolski et al, 1983;Klein et al, 1990;Kukinyi et al, 1996;Chiao et al, 1995;Theiss, 2012). Numeric inversion approaches, armed with dielectric models, are also used for analyzing optical data acquired from spectroscopic ellipsometry, which are based on measured polarized-light reflection quantities of a structure that are directly related its optical functions.…”

“…A common oscillator-like ̂ -formulation for a collection of non-interacting atoms (zero Lorentz field-correction factor) for a group of Lorentz oscillators with diverse resonance frequencies , quantum-mechanical strengths (~ ) with ∑ , and damping frequencies (broadening linewidths) is given by (Navarrete et al, 1990;Tauc, 1972;Tauc, 1979;Heavens, 1991;Azzam & Bashara, 1987;Ward, 1994;Dragoman & Dragoman, 2002;Stenzel, 2005;Poelman & Smet, 2003;Adachi, 1991;Jellison & Modine, 1996;Chambouleyron & Martínez, 2001;Truong & Tanemura, 2006;Kasap & Capper, 2006;Christman, 1988;Rogalski & Palmer, 2000;Palik, 1998;Dressel & Grüner, 2002;Reitz et al, 1993;Jackson, 1998;Born & Wolf, 2002;Dresselhaus, 2001;Bassani & Parravicini, 1975;Sólyom, 2009)…”

“…Regarding optical properties of undoped a-Se films, a lot of work were carried out for decades, but this issue is still continue to receive research attention as the existing information on their optical behavior is still less than adequate and disperse. The reported literature values of room-temperature band-gap energy of undoped or slightly-doped a-Se scatter greatly in the range (1.4 2.2 eV) and the values of their optical constants vary from one work to another (Mott & Davis, 1979;Tan, 2006;Tan et al, 2007;Tan et al, 2006;Vautier et al, 1988;Bettstelleret al, 1993;Adachi & Kao1980;Kotkata & Abdel-Wahab, 1990;Kotkata et al, 2009;Navarrete et al, 1990;Solieman & Abu-Sehly, 2010;Nagels et al, 1995;Tichy et al, 1996;Nagels et al, 1997;. The diversity of these findings may be related to different film thicknesses, to dissimilar methods and preparation conditions used in film deposition, and to variability of experimental techniques used to characterize optical response of studied films.…”

“…The diversity of these findings may be related to different film thicknesses, to dissimilar methods and preparation conditions used in film deposition, and to variability of experimental techniques used to characterize optical response of studied films. Discrepancies in reported optical properties of undoped a-Se films may also be linked to techniques employing different theoretical formulations for analyzing measured optical data, and to the interband transition mechanisms and band-energy structure models used for interpreting the optical absorption phenomena operative in them (Mott & Davis, 1979;Tan et al, 2006;Vautier et al, 1988;Bettstelleret al, 1993;Mulama et al, 2014;Benkhedir, 2006;Adachi & Kao1980;Kotkata & Abdel-Wahab, 1990;Kotkata et al, 2009;Navarrete et al, 1990;Solieman & Abu-Sehly, 2010;Nagels et al, 1995;Tichy et al, 1996;Nagels et al, 1997;.…”