Vertically oriented germanium nanowires grown from gold colloids on silicon substrates and subsequent gold removal.

A linker-free method to deposit citrate-stabilized Au colloids onto hydrogen-terminated Si by acidifying the Au colloid solution with HF or HCl is presented. This method prevents oxide formation and provides a model system for studying orientation control of nanowires by epitaxy. Conditions are reported that result in vertically oriented Ge nanowires of uniform diameter and length on Si(111). We then present a method to remove Au catalysts from the nanowires with aqueous triiodide and HCl.