1205.6834 (Scott A. Norris)

A chemically-driven finite-wavelength instability in ion-irradiated
compound semiconductors    [PDF]

Scott A. Norris

In recent years, observations of highly-ordered, hexagonal arrays of self-organized nanostructures on solids irradiated by ion beams at normal incidence have excited interest in this phenomenon as a potential route to high-throughput, low-cost manufacture of nanoscale devices. Experimental and theoretical work is converging on the hypothesis that these ordered structures only appear when irradiating binary, or impurity-laced monatomic targets. An important question now is to identify the fundamental mechanism behind structure formation, and recently many studies on this topic have appeared. Two theories have recently been separately proposed. One well-studied analytical model predicts ordered patterns driven fundamentally by a morphological instability. However, such patterns are also observed in numerical simulations for which the driving mechanism is a compositional instability. To identify testable differences between the two theories, we propose here a generalized framework containing parameter regimes associated with both previously-proposed mechanisms. Analyzing the full model, we find that the compositional mechanism also contains all of the necessary ingredients for ordered patterns, and is clearly differentiated from the morphological mechanism by differences in parameter values and predictions on experiment. This suggests the utility of specific atomistic and experimental measurements to guide continued theoretical progress.

View original: http://arxiv.org/abs/1205.6834