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Title: Anisotropy in hydrogenated amorphous silicon films as observed using polarized FTIR-ATR spectroscopy

Abstract

The authors used polarized attenuated total reflection (ATR) measurements together with Fourier transform infrared (FTIR) spectroscopy to investigate the vibrational spectra of hydrogenated amorphous silicon (a-SiH{sub x}) films 0.5--1.0 microns in thickness. They deposited the films using hot-wire or plasma-enhanced chemical vapor deposition methods (HWCVD or PECVD, respectively) on crystalline silicon and cadmium telluride substrates. The ATR technique gave a spectral range from 2,100--400 cm{sup {minus}1}, although the Si-H wagging mode absorption band at 640 cm{sup {minus}1} was somewhat distorted in the a-SiH{sub x}/Si samples by impurity and lattice absorption in the silicon ATR substrates. They report the identification of a Si-O-C impurity band with maximum intensity at 1,240--1,230 cm{sup {minus}1}. The assignment of this band to a Si-O-C vibration is supported by secondary-ion mass spectrometry (SIMS) measurements. The polarized FTIR-ATR spectra of HWCVD and PECVD a-SiH{sub x} films on <111> Si ATR substrates show that the impurity dipoles are oriented strongly parallel to the film growth direction. The wagging mode absorbance band is more intense in the film plane. This trend is less pronounced for the Si-H stretching vibrations. These observations are consistent with some degree of anisotropy or medium-range order in the films. The anisotropy in the Si-Hmore » bands may be related to residual stress in the films. The scanning electron microscopy (SEM) analyses of the samples offer additional evidence of bulk structural anisotropy in the a-SiH{sub x}/Si films. However, the Si-O-C impurity band was not observed in the polarized ATR-FTIR spectra of the a-SiH{sub x}/CdTe samples, thus indicating that the Si substrates influence formation of the impurity in the a-SiH{sub x}/Si films.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab., Golden, CO (US)
OSTI Identifier:
20107919
Resource Type:
Conference
Resource Relation:
Conference: 1999 Materials Research Society Spring Meeting, San Francisco, CA (US), 04/05/1999--04/09/1999; Other Information: PBD: 1999; Related Information: In: Amorphous and heterogeneous silicon thin films: Fundamentals to devices -- 1999. Materials Research Society symposium proceedings: Volume 557, by Branz, H.M.; Collins, R.W.; Okamoto, Hiroaki; Guha, S.; Schropp, R. [eds.], 908 pages.
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; SILICON; AMORPHOUS STATE; HYDROGEN ADDITIONS; CHEMICAL VAPOR DEPOSITION; IMPURITIES; LATTICE VIBRATIONS; ANISOTROPY; MICROSTRUCTURE; CHEMICAL BONDS

Citation Formats

Webb, J D, Gedvilas, L M, Crandall, R S, Iwaniczko, E, Nelson, B P, Mahan, A H, Reedy, R, and Matson, R J. Anisotropy in hydrogenated amorphous silicon films as observed using polarized FTIR-ATR spectroscopy. United States: N. p., 1999. Web.
Webb, J D, Gedvilas, L M, Crandall, R S, Iwaniczko, E, Nelson, B P, Mahan, A H, Reedy, R, & Matson, R J. Anisotropy in hydrogenated amorphous silicon films as observed using polarized FTIR-ATR spectroscopy. United States.
Webb, J D, Gedvilas, L M, Crandall, R S, Iwaniczko, E, Nelson, B P, Mahan, A H, Reedy, R, and Matson, R J. 1999. "Anisotropy in hydrogenated amorphous silicon films as observed using polarized FTIR-ATR spectroscopy". United States.
@article{osti_20107919,
title = {Anisotropy in hydrogenated amorphous silicon films as observed using polarized FTIR-ATR spectroscopy},
author = {Webb, J D and Gedvilas, L M and Crandall, R S and Iwaniczko, E and Nelson, B P and Mahan, A H and Reedy, R and Matson, R J},
abstractNote = {The authors used polarized attenuated total reflection (ATR) measurements together with Fourier transform infrared (FTIR) spectroscopy to investigate the vibrational spectra of hydrogenated amorphous silicon (a-SiH{sub x}) films 0.5--1.0 microns in thickness. They deposited the films using hot-wire or plasma-enhanced chemical vapor deposition methods (HWCVD or PECVD, respectively) on crystalline silicon and cadmium telluride substrates. The ATR technique gave a spectral range from 2,100--400 cm{sup {minus}1}, although the Si-H wagging mode absorption band at 640 cm{sup {minus}1} was somewhat distorted in the a-SiH{sub x}/Si samples by impurity and lattice absorption in the silicon ATR substrates. They report the identification of a Si-O-C impurity band with maximum intensity at 1,240--1,230 cm{sup {minus}1}. The assignment of this band to a Si-O-C vibration is supported by secondary-ion mass spectrometry (SIMS) measurements. The polarized FTIR-ATR spectra of HWCVD and PECVD a-SiH{sub x} films on <111> Si ATR substrates show that the impurity dipoles are oriented strongly parallel to the film growth direction. The wagging mode absorbance band is more intense in the film plane. This trend is less pronounced for the Si-H stretching vibrations. These observations are consistent with some degree of anisotropy or medium-range order in the films. The anisotropy in the Si-H bands may be related to residual stress in the films. The scanning electron microscopy (SEM) analyses of the samples offer additional evidence of bulk structural anisotropy in the a-SiH{sub x}/Si films. However, the Si-O-C impurity band was not observed in the polarized ATR-FTIR spectra of the a-SiH{sub x}/CdTe samples, thus indicating that the Si substrates influence formation of the impurity in the a-SiH{sub x}/Si films.},
doi = {},
url = {https://www.osti.gov/biblio/20107919}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {7}
}

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