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 email@example.com
Revised: 19 April 2008
Published online: 3 July 2008
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 CV =x2CGe +(1-x)CSi, where CGe and CSi are specific heat of pure germanium and silicon nanowires respectively.
PACS: 61.46.-w – Nanoscale materials / 61.48.De – Structure of carbon nanotubes, boron nanotubes, and closely related graphitelike systems (for structure of hollow nanowires, see 61.46.Np) / 65.40.-b – Thermal properties of crystalline solids
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008