Nano-hole formation on gold surface using scanning tunnelling microscope

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, CO₂, H₂O or C₂H₅OH mixed with nitrogen gas; H₂–Ar₂ mixture) were applied in this study. Only the presence of ethanol vapour or water vapour helped to produce nano-holes when positive voltage pulse were superimposed on the sample. Furthermore, the existence of the critical vapour pressure of H₂O or C₂H₅OH in the box was important in the modification of the gold surface and the etching process had an unitary rate when above critical vapour pressure. The linear relationship between the hole surface and the pulse duration was observed. We suggest that an anodic oxidation process of the gold surface under a voltage pulse and a place-exchange mechanism, involving the lifting of gold atoms in the surface monolayer, are relevant in nano-hole formation on the gold surface with STM. This process assisted by atom diffusion, due to the electric field built between the tip and the sample during the voltage pulse, explains the exceptional nano-hole geometry.