Cryogen-free variable-temperature Kelvin probe force microscopy for probing local chemical potential in a graphene heterostructure

TL;DR

This paper introduces a cryogen-free, variable-temperature Kelvin probe force microscopy system capable of stable, high-sensitivity measurements of local chemical potential in graphene heterostructures across a wide temperature range.

Contribution

The development of a stable, cryogen-free KPFM system with enhanced sensitivity and temperature control for probing local electronic properties in 2D materials.

Findings

Detected spatial electronic inhomogeneities in graphene

Observed temperature-dependent chemical potential variations

Confirmed linear band dispersion near charge neutrality point

Abstract

We report the development of a variable-temperature Kelvin probe force microscopy (KPFM) system capable of stable and highly sensitive operation over a wide temperature range based on a GM-cooler-based cryogen-free cryostat. The system incorporates a custom-designed phase-locked loop and automatic gain control, along with passive vibration isolation, enabling precise measurements of local chemical potential even under cryogenic conditions. We demonstrate the performance of this setup by measuring hBN encapsulated monolayer graphene (MLG), revealing spatially resolved electronic inhomogeneities and charge puddles. Our measurements clearly capture temperature-dependent variations in the chemical potential near the charge neutrality point (CNP), consistent with the linear band dispersion of MLG and interaction-driven renormalization of Fermi velocity. This work highlights the robust sensitivity and stability of our system, making it a versatile local probe of quantum phases in van der Waals heterostructures.