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H Evolution from Nano-Crystalline Silicon- Comparison of Simulation and Experiment

Published online by Cambridge University Press:  21 March 2011

R. Biswas
Affiliation:
Department of Physics and Astronomy, Microelectronics Research Center and Ames Laboratory-USDOE, Iowa State University, Ames, Iowa 50011
B. C. Pan
Affiliation:
Department of Physics and Astronomy, Microelectronics Research Center and Ames Laboratory-USDOE, Iowa State University, Ames, Iowa 50011 Department of Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
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Abstract

The temperature dependent H evolution from a-Si:H provides unique information on the H-bonding and microstructure. Traditional undiluted a-Si:H films show a high temperature H-evolution peak near 600°C. However device-quality compact nanocrystalline silicon films grown near the phase boundary of amorphous and microcrystalline growth show a new low temperature H- evolution peak near 400°C in addition to a second high temperature peak near 600°C. The origin of this peak cannot be attributed to microvoids or a substantial density of dihydride species typical of porous low-temperature films. We have simulated the H evolution using a molecular dynamics generated model of nanocrystalline silicon, where nano-crystallites reside in a background amorphous matrix. An excess density of H occurs at the crystallite surface. We find a low temperature evolution peak at 250-400°C, where the H-evolution starts from the surface of the nano-crystallite. In addition there is a higher temperature peak at 700-800°C providing good agreement with H-evolution measurements. The mobile H is found to exist in both the bond-centered type of species and H2 molecules – which has implications for H-diffusion models.

Type
Research Article
Copyright
Copyright © Materials Research Society 2004

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References

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