Morphology and composition of Au catalysts on Ge(111) obtained by thermal dewetting

We investigate the chemical and morphological structure of the Au nanodots on Ge(111), which serve as catalysts for the formation of epitaxial Ge nanowires. We show that dewetting of an Au film on Ge(111) gives rise to a thin Au-Ge wetting layer and Au-Ge dots. These dots are crystallized but not with a single crystallographic orientation. Thanks to the spatially resolved x-ray and transmission electron microscopy measurements, a chemical characterization of both binary Au-Ge catalysts and wetting layer is obtained at the nanoscale. We show that Ge vertical growth is achieved even without an external Ge supply.