An ab initio approach to anisotropic alloying into the Si(001) surface

TL;DR

This study uses density functional theory and kinetic Monte Carlo simulations to investigate the initial stages of alloying silver and indium on silicon surfaces, revealing anisotropic growth patterns and temperature-dependent behaviors.

Contribution

It introduces a comprehensive model combining DFT calculations and kinetic Monte Carlo simulations to understand bimetallic alloying on silicon surfaces, highlighting anisotropic growth mechanisms.

Findings

Effective nucleation of Ag and In atoms observed.

Formation of orthogonal atomic chains during growth.

Anisotropic two-dimensional lattice ordering is possible.

Abstract

Employing density functional theory calculations we explore initial stage of competitive alloying of co-deposited silver and indium atoms into a silicon surface. Particularly, we identify respective adsorption positions and activation barriers governing their diffusion on the dimer-reconstructed silicon surface. Further, we develop a growth model that properly describes diffusion mechanisms and silicon morphology with the account of silicon dimerization and the presence of C-type defects. Based on the surface kinetic Monte Carlo simulations we examine dynamics of bimetallic adsorption and elaborate on the temperature effects on the submonolayer growth of Ag-In alloy. A close inspection of adatom migration clearly indicates effective nucleation of Ag and In atoms, followed by the formation of orthogonal atomic chains. We show that the epitaxial bimetal growth might potentially lead to exotic ordering of adatoms in the form of anisotropic two-dimensional lattices via orthogonal oriented single-metal rows. We argue that this scenario becomes favorable provided above room temperature, while our numerical results are shown to be in agreement with experimental findings.