Size effects in near-ultraviolet Raman spectra of few-nanometer-thick silicon-oninsulator nanofilms
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Date
2016-04
Authors
Poborchii, Vladimir
Morita, Yukinori
Tada, Tetsuya
Geshev, Pavel I.
Utegulov, Zhandos
Volkov, Alexey
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Applied Physics
Abstract
We have fabricated Si-on-insulator (SOI) layers with a thickness h1 of a few nanometers and
examined them by Raman spectroscopy with 363.8 nm excitation. We have found that phonon and
electron confinement play important roles in SOI with h1<10 nm. We have confirmed that the
first-order longitudinal optical phonon Raman band displays size-induced major homogeneous
broadening due to phonon lifetime reduction as well as minor inhomogeneous broadening due to
wave vector relaxation (WVR), both kinds of broadening being independent of temperature. Due to
WVR, transverse acoustic (TA) phonons become Raman-active and give rise to a broad band in the
range of 100–200 cm 1. Another broad band appeared at 200–400 cm 1 in the spectrum of SOI is
attributed to the superposition of 1st order Raman scattering on longitudinal acoustic phonons and
2nd order scattering on TA phonons. Suppression of resonance-assisted 2-nd order Raman bands in
SOI spectra is explained by the electron-confinement-induced direct band gap enlargement compared
to bulk Si, which is confirmed by SOI reflection spectra. Published by AIP Publishing.
[http://dx.doi.org/10.1063/1.4947021]
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Citation
Vladimir Poborchii, Yukinori Morita, Tetsuya Tada, Pavel I. Geshev, Zhandos N. Utegulov, Alexey Volkov. 2016. Size effects in near-ultraviolet Raman spectra of few-nanometer-thick silicon-oninsulator nanofilms. Journal of Applied Physics