Scanning probe microscopy and potentiometry using a junction field effect transistor based sensor

Abstract

Scanning tunneling microscopy in its conventional form relies on a steady state tunneling current of 10−12–10−6 A. However, for various applications, it is desirable to reduce the current load to a minimum. Here, we present first experiments using a cooled junction field effect transistor in open gate operation, thereby reducing the DC-current to less than 10−19 A. This enables almost ideal measurements of the local electrochemical potential on a surface. Various methods applying dynamic modes can be used to maintain a constant distance between the scanning probe and the sample surface. Here, we use an AC-bias applied to the sample and a lock-in amplifier connected to the preamplifier to evaluate the conductance of the tunneling gap.