Atomic Order in Non-Equilibrium Silicon-Germanium-Tin Semiconductors

TL;DR

This study uses advanced atom probe tomography to analyze atomic arrangements in non-equilibrium SiGeSn semiconductors, revealing unexpected element interactions that influence material properties.

Contribution

It provides the first detailed 3D atomic distribution analysis of non-equilibrium SiGeSn alloys, uncovering novel Sn-Si repulsive interactions affecting atomic order.

Findings

Detected Sn-Si repulsive interactions

Observed deviation from ideal solid solution

Supported findings with first-principles calculations

Abstract

The precise knowledge of the atomic order in monocrystalline alloys is fundamental to understand and predict their physical properties. With this perspective, we utilized laser-assisted atom probe tomography to investigate the three-dimensional distribution of atoms in non-equilibrium epitaxial Sn-rich group IV SiGeSn ternary semiconductors. Different atom probe statistical analysis tools including frequency distribution analysis, partial radial distribution functions, and nearest neighbor analysis were employed in order to evaluate and compare the behavior of the three elements to their spatial distributions in an ideal solid solution. This atomistic-level analysis provided clear evidence of an unexpected repulsive interaction between Sn and Si leading to the deviation of Si atoms from the theoretical random distribution. This departure from an ideal solid solution is supported by first principal calculations and attributed to the tendency of the system to reduce its mixing enthalpy throughout the layer-by-layer growth process.