Construction of a Versatile Ultra-Low Temperature Scanning Tunneling Microscope

TL;DR

This paper reports the development of a versatile ultra-low temperature scanning tunneling microscope capable of operating at 30 mK in magnetic fields up to 6 T within ultrahigh vacuum, with rapid sample loading and high stability.

Contribution

It introduces a novel DR-based ULT-STM with unique features like quick cooling, UHV sample loading, and high magnetic field stability, expanding experimental capabilities in low temperature physics.

Findings

Operates at 30 mK and 6 T magnetic field

Allows UHV tip and sample loading with quick cooldown

Maintains high stability during magnetic field sweep

Abstract

We constructed a dilution-refrigerator (DR) based ultra-low temperature scanning tunneling microscope (ULT-STM) which works at temperatures down to 30 mK, in magnetic fields up to 6 T and in ultrahigh vacuum (UHV). Besides these extreme operation conditions, this STM has several unique features not available in other DR based ULT-STMs. One can load STM tips as well as samples with clean surfaces prepared in a UHV environment to an STM head keeping low temperature and UHV conditions. After then, the system can be cooled back to near the base temperature within 3 hours. Due to these capabilities, it has a variety of applications not only for cleavable materials but also for almost all conducting materials. The present ULT-STM has also an exceptionally high stability in the presence of magnetic field and even during field sweep. We describe details of its design, performance and applications for low temperature physics.