Lattice Vibrational Modes and their Frequency Shifts in Semiconductor Nanowires

TL;DR

This study uses first-principles calculations to analyze vibrational modes in silicon nanowires, revealing size-dependent frequency shifts and their detectability via Raman scattering, aiding nanowire size estimation.

Contribution

It provides a detailed theoretical analysis of vibrational modes in SiNWs and links these modes to Raman measurements for size estimation.

Findings

Optical modes exhibit red shift with decreasing diameter.

Confined modes show blue shift as size decreases.

Vibrational modes are detectable by Raman scattering.

Abstract

We have performed first-principles calculations to study the lattice vibrational modes and their Raman activities in silicon nanowires (SiNWs). Two types of characteristic vibrational modes are examined: high-frequency optical modes and low-frequency confined modes. Their frequencies have opposite size dependence with a red shift for the optical modes and a blue shift for the confined modes as the diameter of SiNWs decreases. In addition, our calculations show that these vibrational modes can be detected by Raman scattering measurements, providing an efficient way to estimate the size of SiNWs.