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An Equilibrium Based Mean-Field Model for Diffusion in Solids With a Distributed Density of States

Published online by Cambridge University Press:  15 February 2011

A. J. Franz  and
J. L. Gland
A. J. Franz
Affiliation:
Dept. of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109–2136
J. L. Gland
Affiliation:
Dept. of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109–2136
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Abstract

Determination of transport mechanisms and energetics in amorphous silicon presents an interesting modeling challenge. Transport in amorphous silicon films is likely to involve energetically distributed traps and mobile species, as in the case of hydrogen and electron diffusion. Detailed kinetic models using discrete energy levels have been developed, however, the density of states of the diffusing species in amorphous silicon is likely to be continuous and distributed, due to the amorphous nature of the films. We have developed a mean-field, equilibrium based model which utilizes a continuous density of states for the diffusing species. The transport in amorphous silicon is modeled as a function of a gradient in the quasi-chemical potential, rather than concentration, of the diffusing species. The model is applicable when the local equilibration processes are fast relative to the transport process. This approach is extremely numerically efficient, as well as flexible, allowing for modeling of tracer experiments, such as deuterium diffusion in a-Si:H films, and possible changes in density of states with time, temperature, and diffusing species concentration. We demonstrate the utility of the model by simulating hydrogen evolution from a-Si:H films.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 469: Symposium E – Defects and Diffusion in Silicon Processing , 1997 , 517
Copyright
Copyright © Materials Research Society 1997

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References

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