Eur. Phys. J. B 63, 425-430 (2008)
https://doi.org/10.1140/epjb/e2008-00253-3

Lattice dynamics investigations of SiGe core-shell nanowires

Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, Xiangtan University, Xiangtan, 411105, P.R. China and Department of Physics, Xiangtan University, Xiangtan, 411105, P.R. China

Corresponding author: ^a yingzhang@xtu.edu.cn

Received: 29 January 2008
Revised: 19 April 2008
Published online: 3 July 2008

Abstract

We present results from lattice dynamics calculations on the phonon modes and specific heat of SiGe core-shell nanowires. The results show that phonon dispersion relation of SiGe nanowires consists of four acoustic branches. The frequency of the first optical mode at Γ point shifts to low frequency as the Ge concentration is increasing. There are three strong peaks in the spectra of density of states. The peaks at 9.0 THz and 15.0 THz can be attributed to the high frequency Ge-Ge and Si-Si bond vibration. The broad peak around 3.0 THz of pure silicon nanowire corresponds to the transverse acoustic branch of bulk silicon. Moreover, specific heat of SiGe nanowires increases (decreases) with the increase of the concentration x at low (high) temperature. The specific heat at 300 K can be fitted by C_V =x²C_Ge +(1-x)C_Si, where C_Ge and C_Si are specific heat of pure germanium and silicon nanowires respectively.