2020 Volume 63 Issue 8 Pages 431-436
We have developed scanning tunneling potentiometry (STP) operating in ultrahigh vacuum conditions, which provides us a surface topography and the corresponding electrochemical potential distribution simultaneously in nanometer scale special resolution and µV-level potential sensitivity under a lateral electrical current flowing parallel to the sample surface. Using this setup, we have successfully performed an STP measurement on the Si(111)-7×7 reconstructed surface, which holds metallic surface states. Our observation indicates that not only steps but also phase boundaries of the Si(111)-7×7 surface work as an electrical resistance impeding the conductance through the surface states. From the evaluation of the ratio of conductivity across the one-dimensional line defects to that of the terrace on the Si(111)-7×7 surface, the conductivity of the phase boundary is found five times that of the monolayer-height step.