Atom Manipulation with the Scanning Tunneling Microscope: Nanostructuring and Femtochemistry

Abstract

We briefly survey our recent studies on the “soft” lateral manipulation of atoms and small molecules with a scanning tunneling microscope (STM), whereby the tip-surface forces are mainly employed. Repulsive (pushing) as well as discontinuous (pulling) and continuous (sliding) attractive manipulation modes could be distinguished on Cu(211) for CO molecules and metal atoms, respectively. In the case of pulling of Cu atoms on Cu(111), even very fine details could be discerned, the adparticle may show various movement patterns visiting different surface sites upon the application of different tip forces. Lateral manipulation also allows modifications of the Cu(211) substrate itself in an atom-by-atom manner by releasing atoms from sixfold coordinated kink sites as well as from sevenfold coordinated regular step sites. Furthermore, investigations concerning controlled vertical manipulation with emphasis on “picking up” single CO molecules are reported. The mechanism behind vertical transfer of CO-molecules relates to ultrafast chemical processes. Vertical manipulation implies, besides extending the possibilities for the buildup of nanostructures, the important possibility of creating structurally and compositionally well defined tips, which may eventually lead to the realization of chemical sensitivity with the STM.