Characterization of two fast-turnaround dry dilution refrigerators for scanning probe microscopy

TL;DR

This paper presents the construction and detailed vibrational and thermal characterization of two cryogen-free dilution refrigerator scanning probe microscopes, addressing the challenges of vibrations and cooling performance for quantum material studies.

Contribution

It provides a systematic methodology for characterizing vibrations and thermal performance in cryogen-free SPMs, serving as a reference for future research and development.

Findings

Vibrations at the microscope stage are minimized with customized filtering.

Cooling power and tip electron temperature are effectively characterized.

Cryogen-free SPMs can achieve low vibrations comparable to traditional systems.

Abstract

Low-temperature scanning probe microscopes (SPMs) are critical for the study of quantum materials and quantum information science. Due to the rising costs of helium, cryogen-free cryostats have become increasingly desirable. However, they typically suffer from comparatively worse vibrations than cryogen-based systems, necessitating the understanding and mitigation of vibrations for SPM applications. Here we demonstrate the construction of two cryogen-free dilution refrigerator SPMs with minimal modifications to the factory default and we systematically characterize their vibrational performance. We measure the absolute vibrations at the microscope stage with geophones, and use both microwave impedance microscopy and a scanning single electron transistor to independently measure tip-sample vibrations. Additionally, we implement customized filtering and thermal anchoring schemes, and characterize the cooling power at the scanning stage and the tip electron temperature. This work serves as a reference to researchers interested in cryogen-free SPMs, as such characterization is not standardized in the literature or available from manufacturers.