Shape Transition in the Epitaxial Growth of Gold Silicide in Au Thin Films on Si(111)

TL;DR

This study investigates the shape transition of epitaxial gold silicide islands on Si(111), revealing a critical size where islands change from triangular to trapezoidal, influenced by substrate vicinality and growth conditions.

Contribution

It provides new insights into the shape evolution and growth anisotropy of gold silicide islands on Si(111), highlighting the role of substrate vicinality in shape selection.

Findings

Islands grow as equilateral triangles up to a critical size.

Beyond this size, islands transition to trapezoid shapes.

Growth occurs preferentially along one Si[110] direction due to substrate vicinality.

Abstract

Growth of epitaxial gold silicide islands on bromine-passivated Si(111) substrates has been studied by optical and electron microscopy, electron probe micro analysis and helium ion backscattering. The islands grow in the shape of equilateral triangles up to a critical size beyond which the symmetry of the structure is broken, resulting in a shape transition from triangle to trapezoid. The island edges are aligned along $Si[110]$ directions. We have observed elongated islands with aspect ratios as large as 8:1. These islands, instead of growing along three equivalent [110] directions on the Si(111) substrate, grow only along one preferential direction. This has been attributed to the vicinality of the substrate surface.