Lattice strain at c-Si surfaces: a density functional theory calculation

TL;DR

This study uses density functional theory to analyze how surface relaxation, reconstruction, and oxidation affect lattice strain in crystalline silicon surfaces, impacting precision measurements like the Avogadro constant.

Contribution

It provides detailed computational insights into surface-induced lattice strain in silicon, considering various realistic surface conditions.

Findings

Surface relaxation causes measurable strain in silicon surfaces.

Oxidation and reconstruction significantly alter surface lattice parameters.

Results inform the accuracy of silicon-based measurement standards.

Abstract

The measurement of the Avogadro constant by counting Si atoms is based on the assumption that Si balls of about 94 mm diameter have a perfect crystal structure up to the outermost atom layers. This not the case because of the surface relaxation and reconstruction, the possible presence of an amorphous layer, and the oxidation process due to the interaction with the ambient. This paper gives the results of density functional calculations of the strain components orthogonal to crystal surface in a number of configurations likely found in real samples.