RF-STM measurements of a tip induced quantum dot in Silicon under the influence of a magnetic field at mK temperatures.

Qualifying the suitability of a specific material substrate for quantum computing applications prior to device fabrication would be extremely advantageous. A scanning electrode has been proposed [1] to locally induce a quantum dot in a semiconducting material and interrogate its interaction with buried defects through dispersive readout. This method provides a non-invasive approach to testing material quality at the quantum dot level, while preserving the substrate integrity. To that end, our group has been measuring the bias voltage dependent tip-sample capacitance C_TS(V) on Cl terminated Si samples using an RF tank circuit in a milli Kelvin scanning tunneling microscope (mK-STM). We observed apparent multistate structures in the bias dependent capacitance response. These structures manifest as sets of bright hyperbolas as a function of tip position. Line-like structures were also observed. Here we present measurements showing the evolution of these structure under the influence of an external magnetic field in the range of 0 T to 3 T. Notably, the scan area had to be adjusted after each field due to a slight drift of the STM with magnetic field (a total of ~400 nm over 3 T) which was accomplished by realigning topographic images. Three effects with increasing magnetic field were observed: a shift in the energetic position of the levels, a broadening of the levels and a tightening of the hyperbolas. We will discuss the implication of these observations during the presentation.



[1] Yun-Pil Shim, Rusko Ruskov, Hilary M. Hurst, and Charles Tahan, Appl. Phys. Lett. 114 (15) 152105 (2019). https://doi.org/10.1063/1.5053756