Kelvin Probe Spectroscopy of a Two-Dimensional Electron Gas Below 300 mK

TL;DR

This study employs Kelvin probe spectroscopy with a low-temperature scanning force microscope to measure local electron density in a 2D electron gas, achieving results consistent with transport measurements.

Contribution

It introduces a method for local electron density measurement at sub-300 mK temperatures using Kelvin probe spectroscopy combined with AFM.

Findings

Local electron density measurements agree within 10% of transport data.

The technique works at temperatures below 300 mK.

Capacitor model effectively extracts electron density from frequency shift data.

Abstract

A scanning force microscope with a base temperature below 300 mK is used for measuring the local electron density of a two-dimensional electron gas embedded in an Ga[Al]As heterostructure. At different separations between AFM tip and sample, a dc-voltage is applied between the tip and the electron gas while simultaneously recording the frequency shift of the oscillating tip. Using a plate capacitor model the local electron density can be extracted from the data. The result coincides within 10% with the data obtained from transport measurements.