Combined atom probe and STM study of tip-substrate interactions

Abstract

A combination of an imaging atom probe (field ion microscope with a time-of-flight mass spectrometer) and a scanning tunneling microscope (STM), which are integrated in the UHV-system, has been used to study the tip-substrate interactions after electrical contact and mechanical indentation. After “jump-to-contact” experiments with tungsten tips on a gold substrate ad-atom clusters has been observed in the FIM-images. The imaged clusters can be identified by time-of-flight mass analysis as Au and give evidence for material transfer in sub-monolayer range. The image contrast in the micrographs gives almost no reference to induced lattice defects after this contact experiments. In additional indentation-experiments clearly induced plastic deformation of the tip crystallite can be observed as well as material transfer of several monolayers. The FIM micrographs after field desorption of consecutive atomic layers show the features of these deformations typically into a depth up to 20–25 atomic layers.