Size dependence of lattice constants of semiconductor nanocrystals

TL;DR

This study theoretically investigates how the equilibrium lattice constants of semiconductor nanocrystals like Si, GaAs, and CdSe vary with size, highlighting the effects of surface passivation and strain profiles.

Contribution

It provides detailed insights into size-dependent lattice constant variations and surface effects in semiconductor nanocrystals, which were not thoroughly characterized before.

Findings

Deviations from bulk lattice constants are reduced with surface passivation.

Surface bonds exhibit significant strain, with shorter bonds at the surface.

Passivation decreases lattice constant deviations to about 0.3-0.4%.

Abstract

We have theoretically examined the size dependence of the equilibrium lattice constant of nanocrystals of Si, GaAs and CdSe. While deviations from the bulk lattice constant are as large as 1-2% for unpassivated nanocrystals of Si, the deviations drop to ~ 0.3%-0.4% once the surfaces are passivated. Inspite of the fact that the average equilibrium bond-lengths are bulk-like, we find that the nearest-neighbor bond-length exhibits an unusual strain profile with bulk like bond-lengths in the core and shorter (~ 1%) bonds at the surface.