Reverse Epitaxy of Ge: Ordered and Faceted Surface Patterns


Reverse Epitaxy of Ge: Ordered and Faceted Surface Patterns

Ou, X.; Keller, A.; Helm, M.; Fassbender, J.; Facsko, S.

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: on Ge surfaces irradiation at temperatures above the recrystallization temperature of 250°C leads to self-organized patterns of inverse pyramids. Checkerboard patterns with fourfold 2 symmetry evolve on the Ge (100) surface, whereas on the Ge (111) surface, isotropic patterns with a sixfold symmetry emerge. After high-fluence irradiations, these patterns exhibit well-developed facets. A deterministic nonlinear continuum equation accounting for the effective surface currents due to an Ehrlich-Schwoebel barrier for diffusing vacancies reproduces remarkably well our experimental observations.

Keywords: ion irradiation; pattern formation; negative epitaxy

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Publ.-Id: 18937