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Measurement of Two Deep H Bonding Levels in Device Quality Glow Discharge a-SI:H

Published online by Cambridge University Press:  15 February 2011

A. H. Mahan ,
E. J. Johnson ,
R. S. Crandall  and
H. M. Branz
A. H. Mahan
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401
E. J. Johnson
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401
R. S. Crandall
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401
H. M. Branz
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401
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Abstract

We present the results of H effusion studies on device-quality glow discharge deposited hydrogenated amorphous silicon (a-Si:H) films. We measure the decrease in the amount of Si-H infrared absorption as pieces of an a-Si:H sample are annealed isothermally at temperatures from 425°C to 500°C, until more than 95% of the initial H is evolved. We use the rate equation for loss of H due to annealing to calculate the activation energy for H effusion. For anneals below 500°C we observe two distinct rate processes, a fast process corresponding to release of ∼ 70% of the total H (∼10 at. %) contained in the sample, and a slower process corresponding to effusion of the remainder. The fast loss process yields an activation energy of ∼1.4 eV; this is the energy level widely observed in diffusion coefficient measurements. A similar analysis for the slow loss process yields an activation energy of ∼2.1 eV and a diffusion constant prefactor higher than that for the fast loss process. We suggest that this slow component represents the first determination of the energy depth of the “isolated” H component commonly observed in nuclear magnetic resonance experiments.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 377: Symposium A – Amorphous Silicon Technology 1995 , 1995 , 413
Copyright
Copyright © Materials Research Society 1995

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References

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