Morphological regions and oblique incidence dot formation in a model of surface sputtering

TL;DR

This study models surface morphology changes due to off-normal ion-beam sputtering, revealing conditions for ripple and dot formation, a topography crossover, and growth exponents for surface roughness.

Contribution

It introduces an extended atomistic model with lateral erosion, identifying bounds for ripple formation and conditions for dot formation without sample rotation.

Findings

Upper bound μ≈2 for ripple formation in lateral straggle

Dot formation occurs for longitudinal straggle σ≳1.7 without sample rotation

Observed a crossover from hole to ripple topography over time

Abstract

We study solid surface morphology created by off-normal ion-beam sputtering with an atomistic, solid-on-solid model of sputter erosion. With respect to an earlier version of the model, we extend this model with the inclusion of lateral erosion. Using the 2-dimensional structure factor, we found an upper bound $\mu\simeq 2$, in the lateral straggle $\mu$, for clear ripple formation. Above this upper bound, for longitudinal straggle $\sigma\gtrsim 1.7$, we found the possibility of dot formation (without sample rotation). Moreover, a temporal crossover from a hole topography to ripple topography with the same value of collision cascade parameters was found. Finally, a scaling analysis of the roughness, using the consecutive gradient approach, yields the growth exponents $\beta=0.33$ and 0.67 for two different topographic regimes.