Self-aligned Nanoscale SQUID on a Tip

Abstract

A nanometer-sized superconducting quantum interference device (nanoSQUID) is fabricated on the apex of a sharp quartz tip and integrated into a scanning SQUID microscope. A simple self-aligned fabrication method results in nanoSQUIDs with diameters down to 100 nm with no lithographic processing. An aluminum nanoSQUID with an effective area of \(0.034 \mu m^2\) displays flux sensitivity of \(1.8 \times 10^{−6} \phi_0/Hz^{\frac {1}{2}}\) and operates in fields as high as \(0.6 T\). With projected spin sensitivity of \(65 \mu_B/Hz^{\frac {1}{2}}\) and high bandwidth, the SQUID on a tip is a highly promising probe for nanoscale magnetic imaging and spectroscopy.