Fabricating nanoscale structures on Au surface with scanning tunneling microscope

Nanometer-scale pits and mounds were fabricated on Au surface with a scanning tunneling microscope (STM) by applying voltage pulses between the PtIr tip and the substrate. Applying a positive pulse to the substrate generated a pit on the surface with high probability, while a negative pulse formed a mound. The mechanism of structure formation is inferred to be field evaporation, and the polarity dependence is related to the high threshold value of the PtIr alloy tip for negative field evaporation. Furthermore, the fabricated mound could be removed by applying a positive pulse, suggesting that the STM voltage pulse method may be applied to rewritable ultrahigh density recording.