Vertical SNS weak-link Josephson junction fabricated from only boron-doped diamond

A vertical superconductor/normal conductor/superconductor (SNS) weak-link Josephson junction has been successfully fabricated from only homoepitaxial diamond films. Superconducting diamond, normal-state diamond, and superconducting diamond are homoepitaxially grown in a sequence. The temperature dependence of the critical superconducting current was fitted using Likharev's theory of SNS weak-link junctions. When the normal-state-diamond thickness L is much larger than the coherent length in the normal-state-diamond ξₙ, an exponential temperature dependence of normalized critical current was observed, indicating a proximity effect. Shapiro steps in the current-voltage characteristics under microwave irradiation were observed in the junction with Lξₙ.