To study the mechanism of nano-hole formation on a gold surface, with scanning tunnelling microscope (STM), our entire scanning unit was placed in a airtight box. Nanohole formation is sensitive to the chemical environment. Different atmospheres (O 2 , CO 2 , H 2 O or C 2 H 5 OH mixed with nitrogen gas; H 2 -Ar 2 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 H 2 O or C 2 H 5 OH 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.The realization of surface modifications (hole or mound) in the nanometric or atomic range using a scanning probe microscope, and more especially a scanning tunneling microscope (STM), opens new opportunities in the nanolithography field [1, 2]. The typical method for modifying surfaces is to increase the interaction between the tip and the sample by applying a voltage pulse through the junction. Various materials such as graphite [3,4], gold [5, 6] and silicon [7,8] have been investigated. Most of the recent studies on the surface of gold, which were performed either in a ultra-high vacuum chamber or in air, have shown no control in the formation of the hole [9]. Under high vacuum, it is hard to make a clean hole without a mound around it. In air, the surface contamination is important and it is impossible to control the shape and position of the hole. Due to the high surface mobility of gold atoms when experiments are performed in air, the gold modifications are filled in within minutes after their creation [5]. The importance of the chemical composition of the tip-sample's interface has been neglected in these studies. The probability of creating a hole is small, and the location of holes is uncertain against the lateral resolution of STM. in addition, it is not clear why it should not be possible to create holes with negative pulses, as observed in the mound formation. Attempts have been directed towards the understanding of the mechanism of removal of the gold atoms from the gold surface and different schemes have been proposed such as mechanical contact, field evaporation, local heating, electro-and thermomigration, chemical reaction, or combinations of these models (for a review see [10]). The variety of mechanisms used to explain the same phenomenon shows the difficulties encountered in finding a unamb...
