The diamond superconducting quantum interference device

Diamond is an electrical insulator in its natural form. However, when doped with boron above a critical level (0.25 atom %) it can be rendered superconducting at low temperatures with high critical fields. Here we present the realization of a micrometer-scale superconducting quantum interference device (-SQUID) made from nanocrystalline boron-doped diamond (BDD) films. Our results demonstrate that -SQUIDs made from superconducting diamond can be operated in magnetic fields as large as 4 T independent of the field direction. This is a decisive step toward the detection of quantum motion in a diamond-based nanomechanical oscillator.