Utku Kemiktarak , Boston University
Radio-frequency scanning tunneling microscopy
The scanning tunneling microscope (STM) relies upon localized electron tunneling between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. In the 25-year period since its invention, the STM has helped uncover a wealth of phenomena in diverse physical systems ranging from semiconductors to superconductors to atomic and molecular nanosystems. A severe limitation in scanning tunneling microscopy is the low temporal resolution, originating from the diminished high-frequency response of the tunnel current readout circuitry. Here, we overcome this limitation by measuring the reflection from a resonant inductor-capacitor (LC) circuit embedding the tunnel junction, and demonstrate electronic bandwidths as high as 10 MHz. This ~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 fm/\sqrt{Hz} . This sensitivity is on par with the highest available from nanoscale optical and electrical displacement detection techniques, and the RF-STM is expected to be capable of quantum limited position measurements.
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