Interactions of the STM Tip with the Substrate Surface

The atomic processes occurring at the interface of two materials being brought together , separated or moved with respect to each other is central to many technological problems including adhesion, contact formation, friction and wear. At most interfaces of technological relevance the contact occurs at numerous asperities. As a consequence, the tip in the STM as a single asperity and the substrate form a well suited model system to study the fundamental properties of surfaces and interfaces.
The experiments show that already in the usual imaging conditions a transfer of adatoms from the substrate surface to the tip takes place.
The results from mechanical contact and indentation experiments, showing material transfer and neck formation, are in good agreement with computer based simulations (molecular dynamic calculations) on tip-surface interactions.   

W tip before use in STM  (FIM image)

STM image of a stepped (111) Ni surface (300x300 nm, 1 nA, -100 mV)

FIM image after the STM scan of the Ni surface. Transfer of adatoms from steps to the tip occurs

Recent Publication

A. Fian and M. Leisch, “Study on tip-substrate interactions by STM and APFIM”
Ultramicroscopy (2003) Ms623 in print