A study of the spatial variation of electric field in highly resistive metal films by scanning tunneling potentiometry

Electronic transport in highly resistive (but metallic) thin platinum films (approximate to 10 nm) deposited by electron-beam evaporation has been studied by scanning tunneling microscopy and scanning tunneling potentiometry (STP). The films have an average grain size of approximate to 10 nm. On this scale transport through the film is very inhomogeneous. Scattering from grain boundaries (GBs) results in large variations in the local potential resulting in fields as high as 10(4)-10(5) V/cm located near the GB. The reflection coefficient R-g Of electrons at a GB has values between 0.5-0.7 as determined from the STP data. This can be compared to an average (Rg) approximate to 0.9 obtained from an analysis of the bulk resistivity data taken over the temperature range 4.2 K < T < 300 K.