Large output voltage to magnetic flux change in nanoSQUIDs based on direct-write Focused Ion Beam Induced Deposition technique

Abstract

NanoSQUIDs are quantum sensors that excel in detecting a small change in magnetic flux with high sensitivity and high spatial resolution. Here, we employ resist-free direct-write Ga + Focused Ion Beam Induced Deposition (FIBID) techniques to grow W-C nanoSQUIDs, and we investigate their electrical response to changes in the magnetic flux. Remarkably, FIBID allows the fast (3 min) growth of 700 nm×300 nm Dayem-bridge nanoSQUIDs based on narrow nanowires (50 nm wide) that act as Josephson junctions. The observed transfer coefficient (output voltage to magnetic flux change) is very high (up to 1301 µ V/Φ0), which correlates with the high resistivity of W-C in the normal state. We discuss here the potential of this approach to reduce the active area of the nanoSQUIDs to gain spatial resolution as well as their integration on cantilevers for scanning-SQUID applications.

Low-resistivity, high-resolution W-C electrical contacts fabricated by direct-write focused electron beam induced deposition

“…These findings open the route for the direct-write growth of high-resolution electrical contacts on ion-sensitive materials such as high-mobility semiconductor nanowires, oxides, 2D materials, and others. In addition, the performed optimization is useful to create direct electrical contacts to nanoSQUIDs, as required in scanning SQUIDs based on direct-write techniques 36 . It also paves the way towards the fabrication of small-sized Josephson junctions based on superconducting FIBID W-C electrodes connected through these optimized non-superconducting FEBID W-C deposits 31 .…”

Superconducting Materials and Devices Grown by Focused Ion and Electron Beam Induced Deposition

“…Alternatively, the JJs can be fabricated by FIBID. Recently, our group demonstrated the single-step fabrication of a SQUID by connecting two large W-C pads of 50 nm thickness with two W-C nanowires (50 nm in width, and 300nm in length) fabricated by Ga + FIBID [158]. The nanowires form DBs, resulting in two parallel JJs connecting the pads (Figure 8c).…”