Vibrational density of states of silicon nanoparticles

TL;DR

This study uses molecular dynamics to analyze how vibrational states in silicon nanoparticles vary with size, revealing shifts in vibrational modes and density of states that clarify previous experimental-theoretical discrepancies.

Contribution

It provides detailed molecular dynamics analysis of vibrational density of states in silicon nanoparticles, highlighting size-dependent shifts and mode transfers.

Findings

Increased low-frequency density of states in smaller nanoparticles

Shift of transverse optical mode peaks to higher frequencies

Mode transfer from high to intermediate frequencies

Abstract

The vibrational density of states of silicon nanoparticles in the range from 2.3 to 10.3 nm is studied with the help of molecular-dynamics simulations. From these simulations the vibrational density of states and frequencies of bulk-like vibrational modes at high-symmetry points of the Brillouin-zone have been derived. The results show an increase of the density of states at low frequencies and a transfer of modes from the high-frequency end of the spectrum to the intermediate range. At the same time the peak of transverse optical modes is shifted to higher frequencies. These observations are in line with previous simulation studies of metallic nanoparticles and they provide an explanation for a previously observed discrepancy between experimental and theoretical data [C. Meier et al., Physica E, 32, 155 (2006)].