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Diffusion process in BaSi2 film formation by thermal evaporation and its relation to electrical properties

Published online by Cambridge University Press:  22 June 2018

Kosuke O. Hara ,
Keisuke Arimoto ,
Junji Yamanaka  and
Kiyokazu Nakagawa
Kosuke O. Hara*
Affiliation:
Center for Crystal Science and Technology, University of Yamanashi, Kofu, Yamanashi 400-8511, Japan
Keisuke Arimoto
Affiliation:
Center for Crystal Science and Technology, University of Yamanashi, Kofu, Yamanashi 400-8511, Japan
Junji Yamanaka
Affiliation:
Center for Instrumental Analysis, University of Yamanashi, Kofu, Yamanashi 400-8510, Japan
Kiyokazu Nakagawa
Affiliation:
Center for Crystal Science and Technology, University of Yamanashi, Kofu, Yamanashi 400-8511, Japan
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

For fabricating photovoltaic BaSi2 films with controlled carrier density and suppressed oxidation by thermal evaporation, the mechanism determining the film composition from incongruently evaporated BaSi2 must be elucidated. We investigated the effects of source premelting, substrate temperature, and thickness on the structural and electrical properties of evaporated BaSi2 films. It is found by room-temperature deposition that the vapor composition continuously changes from being Ba-rich to being Si-rich. Source premelting suppresses the deposition of Ba-rich vapor. Deposition at 600–700 °C shows that BaSi2 forms through the mutual diffusion of Ba and Si, followed by surface oxidation by residual gas. Surface oxidation can be suppressed by a-axis-oriented growth. By changing the film thickness, the optimum thickness to obtain homogeneous films with suppressed oxidation is revealed. Sufficient diffusion leads to high film resistivities and low electron densities, which demonstrates a close relationship between the film composition and the electrical properties.

Keywords

semiconductingthin filmchemical composition
Type
Invited Feature Paper
Information
Journal of Materials Research , Volume 33 , Issue 16 , 28 August 2018 , pp. 2297 - 2305
Copyright
Copyright © Materials Research Society 2018 

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Footnotes

This paper has been selected as an Invited Feature Paper.

References

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