Low-Noise Diamond-Based DC Nano-SQUIDs

Nanoscale superconducting quantum interference devices (nano-SQUIDs) with Dayem bridge junctions and a physical loop size of 50 nm have been engineered in boron-doped nanocrystalline diamond films using precision Ne-ion beam milling. In an unshunted device, the nonhysteretic operation can be maintained in an applied field exceeding 0.1 T with a high flux-to-voltage transfer function, giving a low flux noise phi(noise) = 0.14 mu phi(0)/root Hz at 1 kHz and a concurrent spin sensitivity of 11 spins/root Hz. At elevated magnetic fields, up to 2 T, flux modulation of the nano-SQUID output voltage is maintained but with an increase in period, attributed to an additional phase bias induced on the nano-SQUID loop by up to 16 vortices per period penetrating the nano-SQUID electrodes.

Automated summary

Nanoscale superconducting quantum interference devices (nano-SQUIDs) with Dayem bridge junctions and a physical loop size of 50 nm have been fabricated in boron-doped nanocrystalline diamond films. The nonhysteretic operation of the unshunted device can be maintained in high magnetic fields, and it exhibits low flux noise and high spin sensitivity. At elevated magnetic fields, the nano-SQUID output voltage shows flux modulation, but with an increased period due to additional phase bias induced by vortices penetrating the nano-SQUID electrodes.