Circuit analysis of an ultrafast junction mixing scanning tunneling microscope

A lumped element circuit model for the operation of a junction mixing scanning tunneling microscope (JM-STM) is presented. Fits from this model show excellent agreement with experimental results in the picosecond time regime. The tip sample capacitance employed in the model was calculated to be 33 fF, using the method of images. By varying the capacitance, various tip/sample geometries can be investigated. Testing the response of the model tunnel junction, for faster electrical pulses, suggests how the JM-STM can be pushed into the femtosecond time regime.