Rapid Electrical Characterization for Superconducting Thin Films Using Gifford-McMahon Cryocoolers

Epitaxially-grown superconducting thin films have many applications in high-speed cryogenic electronics and quantum computing devices. In this project, we design and build a user-friendly and efficient low-temperature measurement system to improve the optimization process for our thin film superconducting epitaxy. Using Gifford-McMahon cryocoolers in inverted geometry, we built three closed-loop He4 cryostats for DC transport, AC transport, and capacitance measurements. We demonstrated an average cool-down time of 2.5hrs from room temperature (300 K) to the base temperature (6-8 K). We evaluated the operation of our cryostats by measuring the superconductivity of niobium on silicon thin films grown by MBE. Our results showed accurate resistance measurements, observation of clear superconducting transition, and cooling times below three hours from room temperature to a stable base temperature below 8K. The final setup will allow our team to rapidly cool superconducting films after each growth cycle to evaluate their superconducting properties, including transition temperature and normal and residual resistivities.