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Measuring Local Physical Properties of Novel Superconductors

Françoise Kidwingira
Katherine Luna
Malcolm Beasley

In looking for new superconductors, a major challenge is often the characterization of imperfect systems. There are quite a few materials where trace superconductivity has been plausibly detected but the investigations were not carried further for the lack of proper characterization tools. The biggest issue is that of volume fraction. It is often the case that only a small part of the sample is superconducting, macroscopic probes can only measure very small signals and give very limited information on the system. Another serious problem is that the materials are often fragile and degrade when exposed to air before the proper characterization can be made.

Together with the thin film fabrication effort in the group, we are implementing an integrated approach that will allow us to get the films from the growth chamber in a UHV environment to a measurement system where they will be characterized by scanning probes. We are in the process of building a multiple probes UHV variable temperature measurement system for the characterization of the physical properties of the thin films grown in the group. The system comprises a UHV sample transport vessel that can carry the samples from the growth chamber to the measurement setup.

The probestation has the capability of supporting 6 independent scanning probes that would perform various measurements on the sample at temperatures between ~6K and 400K. The probes have a scanning range of about 1cm2 and a step size of less than 1 micron. The first 2 probes being implemented are a Micro 4 Point Probe (M4PP, www.capres.com) for 4 points resistance measurements at the micron scale and a Point Contact for Andreev spectroscopy measurements.

Figure 1: UHV cryogenic probestation.

Figure 2: Insie of the probe station with 2 probes mounted: the M4PP and point contact. The circular holes on the walls of the chamber are ports where additional probes will be mounted.

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