Instability types at ion-assisted alloy deposition: from two-dimensional to three-dimensional nanopattern growth

TL;DR

This paper uses linear stability analysis to explore how ion irradiation influences surface pattern formation during alloy film growth, revealing conditions for transitioning from two-dimensional to three-dimensional nanostructures.

Contribution

It introduces a comprehensive analysis of surface instabilities driven by ion irradiation in alloy deposition, identifying key parameters for controlling nanostructure patterns.

Findings

Ion irradiation induces composition-modulated surface patterns.

The ion-to-atom arrival ratio R controls pattern formation.

Different instability regimes lead to stationary or oscillating patterns.

Abstract

Ion irradiation during film growth has a strong impact on structural properties. Linear stability analysis is employed to study surface instabilities during ion-assisted growth of binary alloys. An interplay between curvature-dependent ion-driven and deposition-driven instabilities is investigated. We demonstrate that ion irradiation of growing binary alloys leads to the formation of composition-modulated surface patterns. It is shown that the ion-to-atom arrival ratio R is the pattern control parameter. Close to the instability threshold we identify different regimes of instabilities driven by ion- or deposition-induced surface roughness processes, or roughness-composition feedback interactions. In particular, the synergistic effects of the curvature-dependent displacement and deposition coupling to the preferential sputtering or to the preferential diffusivity are found to induce instabilities and pattern formation. Depending on the film growth and ion-irradiation conditions, the instabilities show stationary or oscillating behavior. The latter one is exclusively connected with ion irradiation. The corresponding phase diagrams are presented in terms of experimentally accessible parameters. This shows an alternative way to control surface patterning and to grow three-dimensional laterally or vertically ordered nanostructures.