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Probing of microvoids in high-rate deposited a-Si: H thin films by variable energy positron annihilation spectroscopy

Published online by Cambridge University Press:  31 January 2011

X. Zou ,
D. P. Webb ,
Y. C. Chan ,
Y. W. Lam ,
Y. F. Hu ,
S. Fung  and
C. D. Beling
X. Zou
Affiliation:
Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong
D. P. Webb
Affiliation:
Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong
Y. C. Chan
Affiliation:
Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong
Y. W. Lam
Affiliation:
Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong
Y. F. Hu
Affiliation:
Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong
S. Fung
Affiliation:
Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong
C. D. Beling
Affiliation:
Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong
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Abstract

In this paper, positron annihilation measurements have been carried out on a-Si: H thin films deposited by plasma-enhanced chemical vapor deposition (PECVD) at high and low rates by means of the variable energy positron beam Doppler-broadening technique. The depth profiles of microvoids in the films grown under different conditions have been determined. We found a smaller void fraction in the surface region of all films compared to the bulk, and a smaller void fraction in low rate than in high growth rate films. By plotting S and W parameters in the (S, W) plane, we have shown that the vacancies in all of the high-rate and low-rate deposited intrinsic samples, and in differently doped low-rate samples are of the same nature, although there appears to be a higher density of defects in the boron than phosphorus doped films. The depth profiles of the microvoid-like defects in the a-Si: H films are extracted by use of the vepfit program.

Type
Articles
Information
Journal of Materials Research , Volume 13 , Issue 10 , October 1998 , pp. 2833 - 2840
Copyright
Copyright © Materials Research Society 1998

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References

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