Room-temperature tunnel current amplifier and experimental setup for high resolution electronic spectroscopy in millikelvin scanning tunneling microscope experiments

The spectroscopic resolution of tunneling measurements performed with a scanning tunneling microscope is ultimately limited by the temperature at which the experiment is performed. To take advantage of the potential high spectroscopic resolution associated with operating a scanning tunneling microscope in a dilution refrigerator we have designed a room-temperature tunnel current amplifier having very small back action on the tunnel contact and allowing to nearly reach the predicted energy resolution. This design is a modification of the standard operational amplifier based tip-biasing current-voltage converter which implements differential voltage sensing and whose back action on the tip voltage is only similar to 2 mu V rms for a 14 MV/A transimpedance and 22 kHz bandwidth. (c) 2006 American Institute of Physics.