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Bonded Hydrogen and Trapped H2 in a-Si1−xGex:H Alloys

Published online by Cambridge University Press:  25 February 2011

E. J. Vanderheiden ,
G. A. Williams ,
P. C. Taylor ,
F. Finger  and
W. Fuhs
E. J. Vanderheiden
Affiliation:
Department of Physics, University of Utah, Salt Lake City, UT 84112
G. A. Williams
Affiliation:
Department of Physics, University of Utah, Salt Lake City, UT 84112
P. C. Taylor
Affiliation:
Department of Physics, University of Utah, Salt Lake City, UT 84112
F. Finger
Affiliation:
Fachbereich Physik, Philipps-Universität Marburg, F.R.G.
W. Fuhs
Affiliation:
Fachbereich Physik, Philipps-Universität Marburg, F.R.G.
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Abstract

1H NMR has been employed to study the local environments of bonded hydrogen and trapped molecular hydrogen (H2) in a series of a-Si1−xGex:H alloys. There is a monotonic decrease of bonded hydrogen with increasing x from ≈ 10 at. % at x = 0 (a-Si:H) to ≈ 1 at. % at x = 1 (a-Ge:H). The amplitude of the broad 1H NMR line, which is attributed to clustered bonded hydrogen, decreases continuously across the system. The amplitude of the narrow 1H NMR line, which is attributed to bonded hydrogen essentially randomly distributed in the films, decreases as x increases from 0 to ≈ 0.2. From x = 0.2 to x ≈ 0.6 the amplitude of the narrow 1H NMR line is essentially constant, and for x ≥ 0.6 the amplitude decreases once again. The existence of trapped H2 molecules is inferred indirectly by their influence on the temperature dependence of the spin-lattice relaxation times, T1. Through T1, measurements it is determined that the trapped H2 concentration drops precipitously between x = 0.1 and x = 0.2, but is fairly constant for 0.2 ≤ x ≤ 0.6. For a-Si:H (x = 0) the H2 concentration is ≈ 0.1 at. %, while for x ≥ 0.2 the concentration of H2 is ≤ 0.02 at. %.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 149: Symposium E – Amorphous Silicon Technology - 1989 , 1989 , 503
Copyright
Copyright © Materials Research Society 1989

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References

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