Low-Noise Diamond-Based D.C. Nano-SQUIDs

Abstract

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-tovoltage transfer function, giving a low flux noise 0.14 / Hz noise 0 ϕ μ ϕ = at 1 kHz and a concurrent spin sensitivity of 11 spins/ 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.