A He3 refrigerated scanning tunneling microscope in high magnetic fields and ultrahigh vacuum

Abstract

We present a scanning tunneling microscope ͑STM͒ designed to operate between 275 mK and room temperature, in magnetic fields up to 14 T and in ultrahigh vacuum ͑UHV͒. The system features a compact STM connected to an UHV compatible 3 He refrigerator fitting into a bottom loading cryostat with a superconducting magnet. In this configuration, the cryostat is sitting on top of the UHV chamber, resulting in a very short distance between the STM access and the experimental position. It further enables proper thermal anchoring of the entire STM setup, allowing millikelvin temperatures to be reached in true UHV conditions. We achieve a hold time of about 40 h at 275 mK and a turnaround time of 10 h between room and base temperature. We demonstrate atomic resolution and present tunneling spectra obtained at 275 mK on the high-T c superconductors Bi 2 Sr 2 CaCu 2 O 8ϩ␦ and YBa 2 Cu 3 O 7Ϫ␦ .

Strong-coupling analysis of scanning tunneling spectra in Bi2Sr2Ca2CuBerthod1, Fasano2, Maggio-Aprile3 et al. 2013Phys. Rev. B

“…53 For the measurements, we used a home-built STM with ultrahigh-vacuum environment and 3 He base temperature. 57 Electrochemically etched iridium tips served as the ground electrode. The bias voltage V was applied to the sample, such that negative (positive) bias refers to occupied (empty) sample states.…”

A Compact and Versatile Scanning Tunnelling Microscope with High Energy Resolution for Use in a 3He Cryostat

“…Some of them combine UHV and very low temperatures [1][2][3][4][5] while other designs operate in conventional cryostats. [6][7][8] The STMs for non-UHV conditions are mostly specialized instruments for investigating heavy fermion superconductors 9 or the spatial dependence of the superconducting proximity effect.…”

Fourfold Structure of Vortex-Core States inBi2Sr2CaCu2O8+δ

“…We performed the measurements with a home-built STM [17] under ultrahigh vacuum. The sample was cleaved in situ at room temperature before cooling and applying the magnetic field and the tunnel junction was made between the (001) sample surface and an electrochemically etched Iridium tip.…”