Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session N31: Advances in scanned probe microscopy
11:30 AM–1:42 PM,
Wednesday, March 16, 2022
Room: McCormick Place W-192A
Sponsoring
Unit:
GIMS
Chair: Chris Jacobsen, Argonne Lab/Northwestern U
Abstract: N31.00002 : Adding RF capabilities to a mK-STM for capacitance measurements
11:42 AM–11:54 AM
Presenter:
Michael Dreyer
(University of Maryland, College Park)
Authors:
Michael Dreyer
(University of Maryland, College Park)
Jonathan J Marbey
(Laboratory for Physical Science)
Robert E Butera
(Laboratory for Physical Sciences)
Our goal is to measure voltage dependent changes in tip-sample capacitance due to the charge occupation of an induced quantum dot in semiconducting materials using our existing mK STM system. To this end, we’ve added a superconducting inductor of ~300 nH in series with the STM tip. The inductor, in combination with the tip stray capacitance - which includes the tip sample capacitance - forms a tank circuit resonator. Therefore, upon sweeping the tip-sample bias, a shift in the resonance frequency (currently ~300 MHz) corresponds to a change in capacitance. The resonator is probed by reflectometry using a directional coupler, bias-Tee and a cryogenic amplifier. With these additions, we can currently achieve the detection of capacitance changes on the order of < 1aF. Here, the sensitivity depends on the resonator Q-factor as well as the overall stray capacitance. Future incremental changes of the setup are expected to increase sensitivity and RF bandwidth. We will present our current setup and initial measurements illuminating the prospects of the system.
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