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The Vibrational Spectrum of a-SiC:H Films in the 500 cm-1 to 9000 cm-1 Range by Ftir Transmission and Photothermal Deflection Spectroscopy

Published online by Cambridge University Press:  21 February 2011

E. Lotter
Affiliation:
Institut für Physikalische Elektronik, Universität Stuttgart, Pfaffenwaldring 47, D-7000 Stuttgart 80, Federal Republic of Germany
G.H. Bauer
Affiliation:
Institut für Physikalische Elektronik, Universität Stuttgart, Pfaffenwaldring 47, D-7000 Stuttgart 80, Federal Republic of Germany
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Abstract

Applying PDS in the energy range from 3000 to 9000 cm-1 considerably improves the sensitivity of vibrational spectroscopy of thin films. In a-SiC:H we have found a large number of absorption features not seen before, which give new insight in structural and compositional properties of these alloys.

In a-SiC:H, in addition to the fundamental and the first and second overtone of C-H stretching modes, O-H vibrations occur at 3500 cm-1 and allow a very sensitive detection of chemical degradation of films due to in-diffusion of water. Combined excitation of C-H stretching and C-H wagging or bending modes give rise to a modified interpretation of the origin of the C-H related absorption features observed in methane based a-SiC:H. The induced absorption of molecular hydrogen together with a band at 7000 cm-1, which results from a combined excitation of C-H bonds and H2 molecules colliding with the C-H, indicates that the amount of H2 increases with C alloying. The C-H + H2 combination mode is very strong compared to the corresponding Si-H + H2 peak observed in pure a-Si:H and signalizes mat a considerable amount of the molecular hydrogen enclosed in voids, containing CH3 or CH2 groups.

Type
Research Article
Copyright
Copyright © Materials Research Society 1992

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