Nanoscale imaging of charge distribution in thin films by modified AFM

An atomic force microscope (AFM) equipped with a conductive tip and working in the contact mode is fully exploited for charge distribution imaging and modification. Measurements of electric properties such as capacitance, trapped charge, or potential of insulating films have up to now mainly been reported from instruments operating in the non-contact mode. An AFM working in the net repulsive force regime (contact mode) would also allow gaining insight into local conductivity and tribological features. A necessary prerequisite was to render conductive commercial cantilevers (Nanoprobe). Finally, it was found that evaporation of 35 nm of titanium yields a mechanically permanent layer with satisfying and stable electric conductivity. Problems not only arise from the preparation of a conductive tip but also from the interpretation of topography and lateral force signals, respectively. The presence of charge manifests itself both in the topography and lateral force signals as additional features. The main purpose of this paper is investigation of local charge distribution in carbon germanium films and its interpretation in the framework of the dedicated model