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Variation of Bandgap in Nanocrystalline Silicon as Monitored by Subgap Photoluminescence

Published online by Cambridge University Press:  10 February 2011

A. Kaan Kalkan ,
Sanghoon Bae ,
Shangcong Cheng ,
Yaozu Wang  and
Stephen J. Fonash
A. Kaan Kalkan
Affiliation:
Electronic Materials and Processing Research Laboratory
Sanghoon Bae
Affiliation:
Electronic Materials and Processing Research Laboratory
Shangcong Cheng
Affiliation:
Materials Characterization Laboratory The Pennsylvania State University, University Park, PA 16802
Yaozu Wang
Affiliation:
Electronic Materials and Processing Research Laboratory
Stephen J. Fonash
Affiliation:
Electronic Materials and Processing Research Laboratory
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Abstract

Infrared PL from νc-Si and nc-Si thin films is a potential spectroscopic tool for sensitive diagnostics of structure and defects. Bhat et al. have shown that the dominant PL band found in νc-Si centered at 0.9 eV cannot be assigned to the amorphous phase, as the energeticaly similar defect band found in a-Si:H (i.e., at 0.9 eV) shows a different temperature dependence and is much broader (i.e., FWHM of 0.15 eV compared to 0.35 eV) [1]. Recently, Carius et al. have observed a gradual lower energy shift of the 0.9 eV PL down to 0.82 eV for nc-Si as the plasma deposition excitation frequency is increased with a corresponding decrease in FWHM from 0.15 0.12 eV, respectively [2]. However, a lower energy shift in optical absorption was not observed, nor did they look for a correlation with the variation of any other physical property. Here, we report a broader range of energy variation for PL from our ECR-PECVD deposited nc-Si films accompanied with an energy shift in optical absorption and variation in dark conductivity and crystallite size. It has been argued that this PL peak in question could arise from the radiative transitions between bandtail states as in the case of ∼1.3 eV PL in a-Si:H or it may be associated with structural defects [2,3]. Our observations support both possibilities.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 507: Symposium A – Amorphous & Microcrystalline Silicon Technology 1998 , 1998 , 291
Copyright
Copyright © Materials Research Society 1998

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References

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