Nanolithography on semiconductor surfaces under an etching solution

We describe a technique for controllably etching nanometer size features into Si(100) and GaAs(100) surfaces with the scanning tunneling microscope while under a (0.05%) HF solution which dissolves oxides. The etching mechanism appears to be due to a field-induced oxide growth followed by a chemical etching of the oxide. With this technique, we can etch features as small as 20 nm in linewidth.