Nano-machining of highly oriented pyrolytic graphite using conductive atomic forcemicroscope tips and carbon nanotubes

Abstract

Sub-100 nm holes were made on a highly oriented pyrolytic graphite (HOPG) surface usinga metal-coated atomic force microscope (AFM) tip and carbon nanotube. HOPG was usedas a substrate (work piece) and a metal-coated (10 nm Cr/30 nm Au) Si AFM tip servedas the other electrode. A negative voltage pulse was applied to the AFM tip tofabricate holes as small as 10 nm in diameter on the HOPG surface with a depth of0.34 nm, which corresponds to a single layer of graphene. We also explored anindividual multi-walled carbon nanotube (MWNT) attached to the AFM tip fornanoscale machining. Unlike the pyramidal shape of the AFM tip, the high aspectratio of a carbon nanotube can make it possible to form deeper holes at evensmaller surface diameter. The hole-formation mechanism is related to the chemicalreaction of graphite with adsorbed water and tunneling electrons from the tip tosubstrate.