Reverse Epitaxy of Ge Surface for Nanopattern Formation

Periodical semiconductor nanostructure arrays have the potential for nano-electronic and nano-optoelectronic application. Besides the conventional low efficiency lithographic techniques broad ion beam erosion is a simple and potentially mass productive technique to fabricate nanostructure patterns on semiconductor surfaces.[1] Based on a “self-organized” erosion process, periodic ripple, hole, dot or tip arrays can be created on various semiconductor surfaces due to the interplay of different processes.[2] However, the main drawback of this method is that the irradiated semiconductor surfaces are amorphized. In this work we report the recent discovery of single crystal Ge nanopattern formation based on a “reverse epitaxy” process. The vacancies created during the ion beam irradiation distribute according to the crystallographic anisotropy, which results in orientation-dependent pattern formation on single crystal Ge surface. The formation of these patterns is interpreted as the result of a surface instability due to an Ehrlich-Schwoebel barrier for ion induced surface vacancies. The simulation of the pattern formation is performed by a continuum equation accounting for the effective surface currents.

[1] Stefan Facsko et al. Science 285, 1551 (1999).