Reverse epitaxy of Ge: ordered and faceted surface patterns.

摘要: Normal incidence ion irradiation at elevated temperatures, when amorphization is prevented, induces novel nanoscale patterns of crystalline structures on elemental semiconductors by a reverse epitaxial growth mechanism: Ge surfaces temperatures above the recrystallization temperature $250\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ leads to self-organized inverse pyramids. Checkerboard with fourfold symmetry evolve (100) surface, whereas (111) isotropic sixfold emerge. After high-fluence irradiations, these exhibit well-developed facets. A deterministic nonlinear continuum equation accounting for effective surface currents due an Ehrlich-Schwoebel barrier diffusing vacancies reproduces remarkably well our experimental observations.