Possible mechanisms of atom transfer in scanning tunneling microscopy

Abstract : Various mechanisms for the sudden transfer of an atom from or to the tip of a scanning tunneling microscope are considered. It is concluded that thermal desorption could be responsible and also that quasi-contact in which the adsorbed atom is in effect touching both surfaces, which would still be separated from each other by 2-4 A can also lead to unactivated transfer via tunneling. For barrier widths as small as 0.5 A, however, tunneling becomes negligible.