Mechanisms of pattern formation and smoothing induced by ion-beam erosion

Abstract

We have investigated bombardment-induced pattern formation and smoothening during Ar + ion erosion of Al 2 O 3 surfaces. The experiments show that ion smoothening of a patterned surface is explained by a mechanism where collisions with near-surface atoms produce an effective downhill current. Quantitative agreement is obtained using ion-collision simulations to compute the magnitude of the surface current. The results lead to predictions for the surface morphology phase diagram as a function of ion energy and incidence angle that substantially agree with experimental results.

Molecular dynamics of single-particle impacts predicts phase diagrams for large scale pattern formation

“…Third, moments are readily obtainable directly by MD simulation, and converge with far fewer trials than do descriptions of the entire crater function used in previous works. Last, although atomistic methods have been used in the past to obtain the amplitude of a single term in a PDE obtained by phenomenological modelling 17,[25][26][27] , we believe this is the first derivation of an entire PDE from MD results. A crucial component of our approach is that the crater function ∆h-and hence the moments M (i) -contains the contributions of both erosion and mass redistribution.…”

Ageing dynamics of ion bombardment induced self-organization processes

“…The effect of the nanodot height increase on the dynamics is two-fold: (1) As the nanodots grow higher, it takes more time to the system to decorrelate from earlier configurations. In other words, the dot creation/annihilation rate decreases and the patterns are preserved for longer times; (2) Mass redistribution, which is a crucial process controlling pattern formation10114041424344, is hindered. With higher dots and a more abrupt topography, the flow of material is also altered and this may result in a slowing down of the pattern dynamics.…”

Mass Redistribution Causes the Structural Richness of Ion-Irradiated Surfaces

“…These studies report rippled surfaces at high angles of deviation from normal incidence, with a transition to a stable flat surface with decreasing . Several authors [7,11,12] have analyzed an impact-induced prompt mass redistribution effect as potentially a small modification of the BH model, sufficient to rescue stability at low angle and perhaps moderating the erosion-driven instability at high angle. We show here that, as far as the stability-instability transition is concerned, the redistribution effect is essentially the whole story-not only the cause of stability at low angle, but also the cause of instability at high angle-and that the erosive effect is essentially irrelevant.…”