The Diamond Superconducting Quantum Interference Device

Diamond is an electrical insulator in its natural form. However, when doped with boron above a critical level (similar to 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 (mu-SQUID) made from nanocrystalline boron-doped diamond (BDD) films. Our results demonstrate that mu-SQUIDs made from superconducting diamond can be operated in magnetic fields as large as 41 Independent of the field direction. This is a decisive step toward the detection of quantum motion in a diamond-based nanomechanical oscillator.