Nanostructure phase and interface engineering via controlled Au self-assembly on GaAs(001) surface

TL;DR

This study explores how temperature controls the morphology, composition, and phase of gold nanostructures self-assembled on GaAs(001), revealing precise manipulation of nanostructure properties through thermal regulation.

Contribution

It demonstrates temperature-dependent control over nanostructure phase, interface, and size during Au self-assembly on GaAs(001), with detailed analysis of growth mechanisms and energetics.

Findings

Formation of pure Au nanoislands below 798 K

Growth of AuGa phase at approximately 798 K

Development of AuGa2 alloy nanostructures at higher temperatures

Abstract

We have investigated the temperature-dependent morphology and composition changes occurring during a controlled self-assembling of thin Au film on the Gallium arsenide (001) surface utilizing electron microscopy at nano and atomic levels. It has been found that the deposition of 2 ML of Au at a substrate temperature lower than 798 K leads to the formation of pure Au nanoislands. For the deposition at a substrate temperature of about 798 K the nanostructures of the stoichiometric AuGa phase were/had been grown. Gold deposition at higher substrate temperatures results in the formation of octagonal nanostructures composed of an AuGa2 alloy. We have proved that the temperature-controlled efficiency of Au-induced etching-like of the GaAs substrate follows in a layer-by-layer manner leading to the enrichment of the substrate surface in gallium. The excess Ga together with Au forms liquid droplets which, while cooling the sample to room temperature, crystallize therein developing crystalline nanostructures of atomically-sharp interfaces with the substrate. The minimal stable cluster of 3 atoms and the activation energy for the surface diffusion Ed=0.816+-0.038eV was determined. We show that by changing the temperature of the self-assembling process one can control the phase, interface and the size of the nanostructures formed.