Controlled nanofabrication of highly oriented pyrolytic graphite with the scanning tunneling microscope

The formation and selective etching of recessed features of various shapes in highly oriented pyrolytic graphite (HOPG) in air were accomplished by use of the scanning tunneling microscope with positive substrate bias voltages of +1500 to +3000 mV and tunneling currents of less than 2 nA. Etching of the surface was restricted to the scan area and only occurred with positive biases, which suggests that etching occurs by an electrochemical mode of oxidation of the graphite under the tip. Lines with widths as small as 10 nm and squares 25 × 25 nm could be formed with monolayer depth (0.34 nm) in the HOPG by varying the time that the tip was rastered over a designated area.