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

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 two-dimensional structure factor, we found an upper bound $\ensuremath{\mu}\ensuremath{\simeq}2$, in the lateral straggle $\ensuremath{\mu}$, for clear ripple formation. Above this upper bound, for longitudinal straggle $\ensuremath{\sigma}\ensuremath{\gtrsim}1.7$, 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 $\ensuremath{\beta}=0.33$ and 0.67 for two different topographic regimes. The results are discussed in the context of the continuum theory.