Scanning Tunneling Potentiometry for Nanoscale Transport Studies

We have developed a scanning tunneling potentiometry (STP) system for study of electrical transport on nanometer length scales. A novel biasing scheme is used to achieve electrochemical potential resolution at the theoretical limits of this measurement - the thermal noise of the tunnel junction. We apply this technique to several materials in order to explore the capabilities of the instrument. These include thin films of Au, the ``bad metal'' SrRuO$_{3}$ and amorphous indium oxide. Homogeneity of transport in these systems is discussed. Work supported initially by the AFOSR and currently by the NSF.