Atom manipulation with the STM: nanostructuring, tip functionalization, and femtochemistry

We briefly survey our recent studies on the soft lateral manipulation of atoms and small molecules with the scanning tunneling microscope (STM), whereby mainly the tip–surface forces are employed. Repulsive (pushing) as well as discontinuous (pulling) and continuous (sliding) attractive manipulation modes could be distinguished on Cu(2 1 1) for CO molecules and metal atoms, respectively. In the case of pulling of Cu atoms on Cu(1 1 1) even finer details could be discerned: the adparticle may show various movement patterns visiting different surface sites upon applying different tip forces. Lateral manipulation also allows modifications of the Cu(2 1 1) substrate itself in an atom-by-atom manner by releasing atoms from six-fold coordinated kink sites and even seven-fold 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 build-up of nanostructures the important possibility of creating structurally and compositionally well defined tips, which may eventually lead to chemical sensitivity with the STM.