Design and performance of an ultra-high vacuum spin-polarized scanning tunneling microscope operating at 30 mK and in a vector magnetic field

TL;DR

This paper presents the design and performance of an ultra-high vacuum, ultra-low temperature spin-polarized STM with vector magnetic field capabilities, enabling advanced atomic and magnetic measurements.

Contribution

It introduces a novel UHV STM system operating at 30 mK with integrated vector magnet and in-situ sample handling, enhancing low-noise, high-resolution spin and electronic measurements.

Findings

Achieved atomic resolution and quasiparticle interference imaging.

Measured electron temperature via superconducting gap of Re(0001).

Demonstrated magnetic imaging of Fe structures.

Abstract

We describe the design and performance of a scanning tunneling microscope (STM) which operates at a base temperature of 30 mK in a vector magnetic field. The cryogenics is based on an ultra-high vacuum (UHV) top-loading wet dilution refrigerator that contains a vector magnet allowing for fields up to 9 T perpendicular and 4 T parallel to the sample. The STM is placed in a multi-chamber UHV system, which allows in-situ preparation and exchange of samples and tips. The entire system rests on a 150-ton concrete block suspended by pneumatic isolators, which is housed in an acoustically isolated and electromagnetically shielded laboratory optimized for extremely low noise scanning probe measurements. We demonstrate the overall performance by illustrating atomic resolution and quasiparticle interference imaging and detail the vibrational noise of both the laboratory and microscope. We also determine the electron temperature via measurement of the superconducting gap of Re(0001) and illustrate magnetic field-dependent measurements of the spin excitations of individual Fe atoms on Pt(111). Finally, we demonstrate spin resolution by imaging the magnetic structure of the Fe double layer on W(110).