First-principles study of the effects of gold adsorption on the Al(001) surface properties

TL;DR

This study uses first-principles calculations to analyze how gold adsorption affects the surface properties of aluminum (001), revealing changes in work-function, surface dipole, and diffusion behavior with varying gold coverage and temperature.

Contribution

It provides a detailed theoretical investigation of gold adsorption effects on Al(001), including adsorption sites, electronic properties, and diffusion, which were not comprehensively studied before.

Findings

Work-function increases with gold coverage.

Surface dipole moment decreases at low coverage.

Gold atoms diffuse into the substrate at elevated temperatures.

Abstract

In this work, we have studied theoretically the effects of gold adsorption on the Al(001) surface, using {\it ab initio} pseudo-potential method in the framework of the density functional theory. Having found the hollow sites at the Al(001) surface as the most preferred adsorption sites, we have investigated the effects of the Au adsorption with different coverages ($\Theta$=0.11, 0.25, 0.50, 0.75, 1.00 ML) on the geometry, adsorption energy, surface dipole moment, and the work-function of the Al(001) surface. The results show that, even though the work-function of the Al substrate increases with the Au coverage, the surface dipole moment decreases with the changes in coverage from $\Theta=0.11$ ML to $\Theta=0.25$ ML. We have explained this behavior by analyzing the electronic and ionic charge distributions. Furthermore, by studying the diffusion of Au atoms in to the substrate, we have shown that at room temperature the diffusion rate of Au atoms in to the substrate is negligible but, increasing the temperature to about 200$^\circ$ C the Au atoms significantly diffuse in to the substrate, in agreement with the experiment.