The on-chip scanning probe with dual niobium nitride nanoscale superconducting quantum interference devices for magnetic imaging at the high temperature

The scanning superconducting quantum interference device (SQUID) microscope is a powerful tool for investigating the microscale magnetic properties of quantum materials. However, the low operating temperature of SQUIDs limits the application of the microscope. In this work, we developed an on-chip probe with dual niobium nitride (NbN) nano-SQUIDs for scanning SQUID microscope. The working temperature of the NbN nano-SQUID on-chip probe was up to 8 K, and it enabled the magnetic imaging of samples at the temperature up to 128 K. We used a gradiometric readout scheme for dual nano-SQUIDs in one probe to reduce the influence of the background magnetic field. Furthermore, we demonstrated the capabilities of both topographic and current imaging by the on-chip probe with spatial resolutions of 1 mu m and 2 mu m, respectively. The advantage of the probe at the high temperature was also demonstrated by the investigation of the superconducting vortices distribution in the yttrium-barium-copper-oxide film.