Confinement effects on the vibrational properties of III-V and II-VI nanoclusters

TL;DR

This study uses first-principles calculations to explore how confinement influences vibrational properties in large colloidal III-V and II-VI nanoclusters, revealing interactions between surface and bulk vibrational modes and size-dependent behaviors.

Contribution

It provides a detailed analysis of vibrational mode interactions and size effects in nanoclusters, highlighting differences between III-V and II-VI materials using first-principles methods.

Findings

Surface and bulk vibrational modes coexist and interact.

Vibrational properties depend on nanocluster size.

Good agreement with experimental Raman and acoustic mode data.

Abstract

We present a first-principles study of the confinement effects on the vibrational properties of thousand atoms (radii up to 16.2 {\AA}) colloidal III-V and II-VI nanoclusters. We describe how the molecular-type vibrations, such as surface--optical, surface--acoustic and coherent acoustic modes, coexist and interact with bulk-type vibrations, such as longitudinal and transverse acoustic and optical modes. We link vibrational properties to structural changes induced by the surface and highlight the qualitative difference between III-Vs and II-VIs. We describe the size dependence of the vibrations and find good agreement for Raman shifts and for the frequency of coherent acoustic modes with experiments.