Bareld Wit, Georg Gramse, Stefan Müllegger,
"Calibrated microwave reflectance in low-temperature scanning tunneling microscopy"
, in Review of Scientific Instruments, Vol. 94, Seite(n) 103702/1-7, 2023
Original Titel:
Calibrated microwave reflectance in low-temperature scanning tunneling microscopy
Sprache des Titels:
Englisch
Original Kurzfassung:
We outline calibrated measurements of the microwave reflection coefficient from the tunnel junction of an ultra-high vacuum low tem-
perature scanning tunneling microscope. The microwave circuit design is described in detail, including an interferometer for an enhanced
signal-to-noise ratio and a demodulation scheme for lock-in detection. A quantitative, in situ procedure for impedance calibration based on
the numerical three-error-term model is presented. Our procedure exploits the response of the microwave reflection signal due to the change
of the tunneling conductance caused by sub-nm variation of the tunneling distance. Experimental calibration is achieved by a least-squares
numerical fit of simultaneously measured conductance and microwave reflection retraction curves at finite conductance. Our method paves
the way for nanoscale microscopy and spectroscopy of dielectric surface properties at GHz frequencies and cryogenic temperatures. This
opens a promising pathway even for dielectric fingerprinting at the single molecule limit.