@article{0ef80e7251c240dda6037a3a448a30cf,
title = "Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method",
abstract = "The direct optical band gap of semiconductors is traditionally measured by extrapolating the linear region of the square of the absorption curve to the x-axis, and a variation of this method, developed by Tauc, has also been widely used. The application of the Tauc method to crystalline materials is rooted in misconception-and traditional linear extrapolation methods are inappropriate for use on degenerate semiconductors, where the occupation of conduction band energy states cannot be ignored. A new method is proposed for extracting a direct optical band gap from absorption spectra of degenerately-doped bulk semiconductors. This method was applied to pseudo-absorption spectra of Sn-doped In2O3 (ITO) - converted from diffuse-reflectance measurements on bulk specimens. The results of this analysis were corroborated by room-temperature photoluminescence excitation measurements, which yielded values of optical band gap and Burstein-Moss shift that are consistent with previous studies on In2O3 single crystals and thin films.",
keywords = "Band gap, Degenerate doping, Diffuse-reflectance, ITO, Photoluminescence",
author = "Alex Dolgonos and Mason, {Thomas O.} and Poeppelmeier, {Kenneth R.}",
note = "Funding Information: This research was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-FG02–08ER46536 and by the Air Products Foundation through the Air Products and Chemicals, Inc. Graduate Fellowship . The authors would like to acknowledge the generous assistance of Heather Arnold in the Department of Materials Science and Engineering at Northwestern University in acquiring photoluminescence spectra. Discussions with Dr. Andreas Klein in the Surface Science Division of the Institute of Materials Science at the Darmstadt University of Technology have also been invaluable in the understanding the energy structure of indium oxide and in the interpretation of optical spectra. Diffuse-reflectance spectra were obtained at the Keck Biophysics Facility at Northwestern University, which is supported by grants from the W. M. Keck Foundation , Northwestern University , the NIH , the Rice Foundation , and the Robert H. Lurie Comprehensive Cancer Center . X-ray diffraction and photoluminescence measurements were performed at Northwestern University utilizing instruments in, respectively, the J. B. Cohen X-ray Diffraction Facility and the Energy Materials Laboratory within the Department of Materials Science and Engineering; both facilities are supported by the MRSEC program of the National Science Foundation ( NSF-DMR-1121262 ). Publisher Copyright: {\textcopyright} 2016 Elsevier Inc. All rights reserved.",
year = "2016",
month = aug,
day = "1",
doi = "10.1016/j.jssc.2016.05.010",
language = "English (US)",
volume = "240",
pages = "43--48",
journal = "Journal of Solid State Chemistry",
issn = "0022-4596",
publisher = "Academic Press Inc.",
}