Spectrophotometric analysis of aluminum nitride thin films

Abstract

The optical functions of AlN thin films deposited on the quartz substrates by the reactive radio frequency magnetron sputtering, such as refractive index, extinction coefficient, optical band gap, and film thickness were determined from the transmittance and reflectance spectra in the range of 190-820 nm. For these analyses, an inverse synthesis method was established after literature survey. The results were doublechecked with a modified envelope method, and compared with those of previous reports. Spectroscopic ellipsometry analyses were performed to confirm the accuracy of the methods. Refractive indices of AlN films in this study were in the range of 1.95-2.05 at 633 nm and 2.26-2.38 at 250 nm, depending on the preparation conditions. The extinction coefficients were small (Ͻ5ϫ10 Ϫ4 ) and nearly constant at low energy region ͑Ͻ2 eV͒, but exhibited various dispersion features at 2.2-3.5 eV, indicating different amount and kinds of defects of AlN films. The absorption coefficient at near-band-gap energy exhibited a strong thickness dependence, resulting in various optical band-gap energies ranging 5.34-5.71 eV.

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

“…6, No. 6;Bashara, 1987Ward, 1994;Dragoman & Dragoman, 2002;Stenzel, 2005;Joo et al, 1999;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). Since transmittance is not an intrinsic property of material, further quantitative analysis of spectra of our air-supported {a-Se film/thick glass substrate}-samples is needed to retrieve optical constants and (≡ /4 ) of their Se-films, their spectral dispersion functions, and to elucidate electronic transitions responsible for optical absorption in such films.…”

“…It is a habit to treat independently a sample's response in different wavelength ranges to find matching dielectric functions and combine them to describe its overall response. The physics and theoretical formulas that describe optical behavior of crystalline materials in the absorption edge and sub-bandgap regions are discussed in literature (Tan, 2006;Tan et al, 2007;Tan et al, 2006;Tauc, 1972;Tauc, 1979;Heavens, 1991;Azzam & Bashara, 1987;Ward, 1994;Dragoman & Dragoman, 2002;Stenzel, 2005;Joo et al, 1999;Poelman & Smet, 2003;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;Dresselhaus, 2001;Bassani & Parravicini, 1975;Sólyom, 2009;O'Leary et al, 1997;Dias da Silva et al, 2004;Liang & Beal, 1976) and Appendix B, the most common of which that can be modified to discuss optical response of amorphous undoped semiconductors are briefed below.…”

“…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.…”

Al-Based Metal Mesh Electrodes for Advanced Touch Screen Panels Using Aluminum Nitride System Optical Absorption Layer

“…Therefore, in the Al-N system thin film with the highly optical absorption and conductivity nature, which was deposited on the nitrogen flow ratio of 16.7%, it is found that there is structural change, from the crystalline aluminum states to the amorphous states including Al-N bond. In general, the AlN thin films are transparent (wideband gap) insulating films [10], [11]. Therefore, it is likely that the amorphous AlN including the fine AlN microcrystalline textures contribute markedly to the optical absorption.…”