Since the carrier density and resistivity of graphene are heavily dependent on the Fermi level, Josephson junctions with graphene as the weak link can have their I-V properties easily tuned by the gate voltage. Most of the previous work on superconductor-graphene-superconductor (SGS) junctions and superconducting quantum interference devices (SQUIDs) were based on mechanically exfoliated graphene, which is not compatible with large scale production. Here, we show that SGS junctions and dc SQUIDs can be easily fabricated from chemical vapor deposition (CVD) graphene and exhibit good electronic properties. The SGS junctions can work without any hysteresis in their electrical characteristics from 1.5 K down to a base temperature of 320 mK, and the critical current can be effectively tuned by the gate voltage by up to an order of magnitude. As a result, dc SQUIDs made up of these junctions can have their critical current tuned by both the magnetic field and the gate voltage.
- Josephson junctions
- superconducting devices