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

Abstract

We present a simple design for a very-low temperature STM for the investigation of mesoscopic superconductors. The nonmagnetic microscope operates in a conventional MOTIVATIONUp to now only a small number of scanning tunnelling microscopes (STM) world-wide are operating at temperatures below 1 K, in high magnetic fields, and achieve high energy resolution E < 1 mV. Some of them combine UHV and very low temperatures 1-5 while other designs operate in conventional cryostats. 6-8 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. [10][11][12] However, a compact STM that combines very low temperatures, operation in magnetic field, and very high energy resolution with robustness, versatility and easy handling is still lacking. Our new setup that is described in the present article fulfills these requirements. It is very small, matching with most commercial low-temperature facilities, does not require elaborate vibration damping and uses only the very modest amount of seven cables. Furthermore, it is already designed for lower temperatures than presented here, is in principle UHV compatible and can be combined with more complex positioning systems. The special physical project, for which purpose our STM was designed, is to investigate the 525 0022-2291/07/0500-0525/0

Creation of equal-spin triplet superconductivity at the Al/EuS interface

“…Spectra were recorded in lock-in technique across a 10 MΩ tunnelling gap, the STM set point was set to a tunnelling current of 400 pA at 4 mV tip voltage and the feedback loop was then stopped before voltage sweeps. The STM used to conduct this study was home built in Konstanz [48] and optimised for high energy resolution spectroscopy at low temperatures [49]. The STM controller used was a commercially available SPM1000 by RHK with a proprietary current amplifier (IVP-300) for STM studies.…”

Single-electron transport through stabilised silicon nanocrystals

“…The scanning region for tunnelling measurements is limited to an area of about 1 μm × 1 μm by the design of our STM. 50 In the present study, we have scanned individual areas as small as 50 nm × 50 nm because of the limited scan speed and the small size of the NCs. NCs have to be well distributed and well attached to the substrate in order to find them within the smallest scan area.…”

A scanning tunneling microscope for a dilution refrigerator

“…In this section the general setup is discussed briefly. The STM is based on the design developed for scan heads used at higher temperatures [6,7] but with a modified tip approach in order to allow for measurements in magnetic fields. The most important features of the design are its versatility and compactness which allows to fit it into the cryostat tail within a superconducting solenoid.…”