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Optical Transitions in Light-Emitting Nanocrystalline Silicon Thin Films

Published online by Cambridge University Press:  15 February 2011

T. Toyama ,
Y. Kotani ,
A. Shimode ,
S. Abo  and
H. Okamoto
T. Toyama
Affiliation:
Department of Physical Science, Graduate School of Engineering Science, Osaka University Toyonaka, Osaka, 560-8531, Japan
Y. Kotani
Affiliation:
Department of Physical Science, Graduate School of Engineering Science, Osaka University Toyonaka, Osaka, 560-8531, Japan
A. Shimode
Affiliation:
Department of Physical Science, Graduate School of Engineering Science, Osaka University Toyonaka, Osaka, 560-8531, Japan
S. Abo
Affiliation:
Department of Physical Science, Graduate School of Engineering Science, Osaka University Toyonaka, Osaka, 560-8531, Japan
H. Okamoto
Affiliation:
Department of Physical Science, Graduate School of Engineering Science, Osaka University Toyonaka, Osaka, 560-8531, Japan
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Abstract

Optical transitions in nanocrystalline Si (nc-Si) thin films with different mean crystal sizes ranging from < 2 nm to ~3 nm have been studied by electroreflectance (ER) spectroscopy. At 293 K, ER signals are observed at 1.20-1.37 eV to be corresponding to fundamental gap in bulk crystalline Si. With a decrease in the mean crystal sizes of nc-Si, the transition energy of the fundamental gap is increased and the ER signal is intensified. The bandgap widening would be due to quantum confinement (QC) in nc-Si, and the increased signal indicates appearance of direct transition nature. The ER signals are also observed at 2.2 eV and at E1 (E0’) direct gap of 3.1-3.4 eV, while photoluminescence (PL) peak energies are located at 1.65-1.75 eV and at 2.3 eV. With the reduced mean crystal size, the 1.7-eV PL peak energy is also increased, suggesting that QC is also responsible for the increased PL peak energy.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 557: Symposium A – Amorphous and Heterogeneous Silicon Thin Films—Fundamentals to Devices—1999 , 1999 , 469
Copyright
Copyright © Materials Research Society 1999

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