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Title: Ion-assisted phase separation in compound films: An alternate route to ordered nanostructures

In recent years, observations of highly ordered, hexagonal arrays of self-organized nanostructures on binary or impurity-laced targets under normal-incidence ion irradiation have excited interest in this phenomenon as a potential route to high-throughput, low-cost manufacture of nanoscale devices or nanostructured coatings. The currently prominent explanation for these structures is a morphological instability driven by ion erosion discovered by Bradley and Shipman; however, recent parameter estimates via molecular dynamics simulations suggest that this erosive instability may not be active for the representative GaSb system in which hexagonal structures were first observed. Motivated by recent experimental and numerical evidence suggesting the likely importance of phase separation during thin-film processing, we here generalize the Bradley-Shipman theory to include the effect of ion-assisted phase separation. The resulting system admits a chemically driven finite-wavelength instability that can explain the order of observed patterns even when the erosive Bradley-Shipman instability is inactive. In a relevant simplifying limit, it also provides an intuitive instability criterion similar to results in thin-film deposition, as well as predictions on pattern wavelengths that agree qualitatively with experimental observations. Finally, we identify a characteristic experimental signature that distinguishes the chemical and morphological instabilities and highlights the need for specific additional experimental datamore » on the GaSb system.« less
Authors:
 [1]
  1. Department of Mathematics, Southern Methodist University, Dallas, TX (United States)
Publication Date:
OSTI Identifier:
22258729
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 20; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COATINGS; DEPOSITION; GALLIUM ANTIMONIDES; IMPURITIES; INSTABILITY; IRRADIATION; MOLECULAR DYNAMICS METHOD; NANOSTRUCTURES; SIMULATION; THIN FILMS; WAVELENGTHS