Catalyst‐Assisted Electroless Flattening of Ge Surfaces in Dissolved‐O 2 ‐Containing Water

Control of the microroughness of Ge surfaces is required to realize field‐effect transistors with high performances. We propose a novel surface‐flattening process for Ge that involves the preferential transformation of surface protrusions on Ge into soluble GeO 2 with the help of a catalyst in water. To carry out this process, we developed a setup comprising a catalyst plate covered with a Pt film in contact with a Ge surface in saturated O 2 ‐dissolved water. The role of the metallic film is to enhance the oxygen reduction reaction in water that accompanies the oxidation of protrusions or microbumps on a Ge surface. After presenting the fundamental etching properties of a Ge surface treated with this metal‐assisted chemical etching method, we demonstrate that our water‐based process creates a flattened Ge surface that has few protrusions with a lateral size on the order of 10 nm.