Size effects in near-ultraviolet Raman spectra of few-nanometer-thick silicon-oninsulator nanofilms

Poborchii, Vladimir
Morita, Yukinori
Tada, Tetsuya
Geshev, Pavel I.
Utegulov, Zhandos
Volkov, Alexey

Publication date

April 2016

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 ...