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Effects of Post Annealing and Material Stability on Undoped and n+ nc-Si:H Films Deposited at 75 °C Using 13.56 MHz PECVD

Published online by Cambridge University Press:  01 February 2011

Czang-Ho Lee ,
Andrei Sazonov  and
Arokia Nathan
Czang-Ho Lee
Affiliation:
Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
Andrei Sazonov
Affiliation:
Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
Arokia Nathan
Affiliation:
Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
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Abstract

The effects of post-deposition annealing and material stability of undoped and n+ nanocrystalline silicon (nc-Si:H) films deposited at 75 °C using standard 13.56 MHz plasma enhanced chemical vapor deposition (PECVD) have been investigated. Electrical, structural, and chemical composition properties of the films at ambient atmosphere were studied before and after the thermal annealing. The dark conductivity (σd) in all films demonstrated high stability against prolonged ambient atmosphere exposure, which can be attributed to stable hydrogen passivation of the grain boundaries. On the other hand, in undoped nc-Si:H films, the σd increases by more than one order of magnitude after annealing in ambient atmosphere, followed by a decrease below the as-grown value. Depending on the annealing temperature, the σd can drop as low as 10-8 S/cm. In n+ nc-Si:H films, the decrease in the σd was lower. However, in undoped nc-Si:H films capped by an amorphous silicon nitride (a-SiN:H), this was not observed. In all films, no significant change in the film microstructure before and after annealing was detected. However, a small decrease in the hydrogen content (CH) accompanied by an increase in the oxygen content (CO) was observed in uncapped undoped nc-Si:H films. It was therefore concluded that the σd is affected by oxygen desorption due to annealing and its absorption from the ambient atmosphere. Based on experimental results, we propose a possible model in terms of hydrogen effusion-assisted oxygen absorption.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 862: Symposium A – Amorphous and Nanocrystalline Silicon Science and Technology–2005 , 2005 , A5.4
Copyright
Copyright © Materials Research Society 2005

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