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Real Time Monitoring of the Crystallization of Hydrogenated Amorphous Silicon

Published online by Cambridge University Press:  01 February 2011

Paul Stradins
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, Colorado 80401, USA
David Young
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, Colorado 80401, USA
Howard M. Branz
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, Colorado 80401, USA
Matthew Page
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, Colorado 80401, USA
Qi Wang
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, Colorado 80401, USA
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Abstract

In-situ real-time optical reflectance spectroscopy is applied to investigate structural changes as hydrogenated amorphous silicon (a-Si:H) loses H and crystallizes at elevated temperature. The interference fringe spectrum (cutoff energy and amplitude) mainly characterize changes in the bulk, while the the crystal Si (c-Si) direct-transition ultra-violet reflectance signatures reveal the presence of any crystalline phase at the surface. Effusion of atomic hydrogen is monitored by a decrease of the interference fringe cutoff energy and is thermally activated with about 1.7 eV. In a-Si:H on glass, optical reflectance spectra are consistent with 2.8 eV activated homogeneous nucleation and growth of a small grain (˜ 100 nm) polycrystalline phase. In contrast, a-Si:H on c-Si crystallizes by solid phase epitaxy with very different spectral kinetics. Our measurements reveal the temperature-time window for thermal crystallization of a-Si:H for photovoltaic device applications, and highlight the versatility of the in-situ spectral reflectance monitoring.

Type
Research Article
Copyright
Copyright © Materials Research Society 2005

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