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Effects of Synchrotron X-Rays on PVD Deposited and Ion Implanted α-Si

Published online by Cambridge University Press:  15 February 2011

Kin Man Yu
Affiliation:
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
Lei Wang
Affiliation:
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
W. Walukiewicz
Affiliation:
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
S. Muto
Affiliation:
Center for Integrated Research in Science and Engineering, Nagoya University, Nagoya 464–01, Japan
S. McCormick
Affiliation:
Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801
J. R. Abelson
Affiliation:
Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801
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Abstract

We have studied the effects of intense x-ray irradiation on the stucture of amorphous Si films. The films were obtained by either physical vapor deposition or by implantation of high energy ions into crystalline Si. They were exposed to different total doses of synchrotron x-rays. From the EXAFS and EXELFS measurements we find that an exposure to x-rays increases the Si coordination number. Also in the PVD films a prolonged x-ray exposure enlarges, by about 2 %, the Si-Si bond length. Raman spectroscopy shows that Si amorphized with high energy ions contains small residual amounts of crystalline material. Irradiation of such films with x-rays annihilates those crystallites resulting in homogenously amorphous layer with a close to four-fold coordination of Si atoms. This rearangement of the local structure has a pronounced effect on the crystallization process of the amorphous films. Thermal annealing of x-ray irradiated ion amorphized films leads to nearly defect free solid phase epitaxy at 500°C. Also we observe a delay in the onset of the crystallization process in x-ray irradiated PVD films. We associate this with a reduced concentration of nucleation centers in the x-ray treated materials.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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References

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