A scanning tunnelling microscopy investigation of gold island formation from an octanethiol self-assembled monolayer on Au(1 1 1)

The release of gold atoms from an octanethiol monolayer on Au(1 1 1) and the subsequent formation of single-layer-high gold islands have been investigated using a scanning tunnelling microscope (STM) in air. When the bias voltage between the STM tip and the sample is above the threshold for water electrolysis, reactive desorption of the thiol molecules takes place leading to the release of gold adatoms. The number of released atoms has been evaluated as a function of exposure to the tip current under both positive and negative bias voltages. Tip-induced ripening of the gold islands, and more interestingly, tip-induced disintegration of small islands are observed.