We present a simple home made solution enabling in-situ RF reflectometry measurements with a millikelvin scanning tunneling microscope (mk-STM). The additions described below were made using RF best practices following similar detection schemes commonly employed in the quantum information science (QIS) community. Using a Niobium STM tip to form a superconductor-insulator-normal metal (SIN) tunnel junction, the evolution of coherence peaks at the SC-gap edge are carefully measured to characterize the RF losses and electron temperature. We further identify impedance matching as a crucial factor to achieve high sensitivity in the reflectometry by tuning the tip-sample capacitance as a function of approach distance. As a demonstration of this capability, we measure a 50x50 nm2 area of island features that have been condensed onto the surface of a gold single crystal. Position dependent reflectometry losses allow us to image island sizes down to a total surface area of 5 nm2 given our current sensitivity.
@article{arxiv.2512.14962,
title = {Adding Radio Frequency Capabilities to a millikelvin Scanning Tunneling Microscope},
author = {Jonathan Marbey and Michael Dreyer and R. E. Butera},
journal= {arXiv preprint arXiv:2512.14962},
year = {2025}
}