Nanofabrication on gold surface with scanning tunneling microscopy

We have developped an experimental technique for writing stable features on an atomically flat gold (111) surface with Scanning Tunneling Microscope (STM). By applying voltage pulses (close to 3 V) across the tunneling junction in controlled atmosphere with the presence of water or ethanol vapour, nano-hole can be produced. The smallest hole formed is 3 nm in diameter and 0.24 nm in depth. This nana-hole represents the loss of about 100 Au atoms in the top atomic layer of gold surface, there is no atomic perturbation seen inside and outside the nano-hole. Different nanostructures (lattice of dots, legends, map, etc.) are fabricated. We report the dependence of the threshold voltage for the formation of a nano-hole on the relative humidity and the existence of a ''critical humidity''. Different tips (Pt-lr, Au, Au-Pd, Ag and W) used, the relationship between the threshold voltage and the relative humidity is basically independent of the tip material. We approve that the mechanism involved in pit formation could be electrochemical in origin.