Radio Frequency Scanning Tunneling Microscopy: Instrumentation and Applications

A severe limitation of the scanning tunneling microscope (STM) is its low temporal resolution, originating from the diminished high-frequency response of the tunnel current readout circuitry. In order to overcome this limitation, we have built a radio-frequency STM (RF-STM). Using this instrument, we can attain electronic bandwidths as high as 10 MHz by measuring the reflection from or transmission through the tunnel junction, which is embedded in a resonant inductor-capacitor (LC) circuit. This $\sim $100-fold bandwidth improvement upon the state-of-the-art translates into fast surface topography as well as delicate measurements in mesoscopic electronics and mechanics. Broadband noise measurements across the tunnel junction using this radio-frequency-STM (RF-STM) have allowed us to perform nanoscale thermometry. Furthermore, we have detected high-frequency mechanical motion with a sensitivity approaching 15 fmHz$^{-1/2}$.