The capacitive origin of the picosecond electrical transients detected by a photoconductively gated scanning tunneling microscope

Abstract

We present experimental results and numerical calculations on the detection of picosecond electrical transients by a photoconductively gated scanning tunneling microscope. We show that the transient signal detected in the tunneling regime is coupled by the 5 fF geometric capacitance between tip and sample leading to a correlation current that is linearly proportional to the tunnel conductance.