Analysis of Strain Fields in Silicon Nanocrystals

TL;DR

This paper investigates the atomistic strain distribution in silicon nanocrystals embedded in silicon dioxide, revealing complex strain behaviors near the surface and reconciling different strain measures.

Contribution

It provides a detailed atomistic analysis of strain fields in silicon nanocrystals, clarifying the apparent contradictions between bond length and volumetric strain.

Findings

Uniform strain in the core of nanocrystals

Nonuniform strain near the surface within 2-3 Å

Reconciliation of bond length and volumetric strain measurements

Abstract

Strain has a crucial effect on the optical and electronic properties of nanostructures. We calculate the atomistic strain distribution in silicon nanocrystals up to a diameter of 3.2 nm embedded in an amorphous silicon dioxide matrix. A seemingly conflicting picture arises when the strain field is expressed in terms of bond lengths versus volumetric strain. The strain profile in either case shows uniform behavior in the core, however it becomes nonuniform within 2-3 \AA distance to the nanocrystal surface: tensile for bond lengths whereas compressive for volumetric strain. We reconsile their coexistence by an atomistic strain analysis.