Abstract
We demonstrate the metal-assisted chemical etching of Ge surfaces in water including dissolved oxygen molecules (O2). It is shown that Ge surfaces around loaded Ag or Pt particles are etched anisotropically in water. The origin of the formation of etch pits on Ge (100) is explained by the enhanced oxidation of Ge to be soluble GeO2 around the metallic particles by their catalytic activity, reducing dissolved O2 to H2O molecules. The reason for the appearance of (111) microfacets is also discussed. Secondly, we apply this electroless chemical etching in water for the nanoscale patterning of Ge surfaces using a cantilever probe in an atomic force microscopy setup. We investigate the effects of probematerials, dissolved-O2 concentration and pressing forces on the etched depth of the Ge surface. The deepest pattern is obtained when both a Pt-coated probe and saturated-dissolved-oxygen water are used.
