Niobium NanoSQUIDs Based on Sandwich Nanojunctions: Performance as a Function of the Temperature

In this paper, an experimental investigation of the main characteristics of a niobium nano Superconducting QUantum Interference Device (nanoSQUID) as a function of the temperature (9–0.3 K) is presented. The nanosensor consists of a niobium superconducting loop
$(0.4 \times 1.0\ \mu\mbox{m}^{2})$
interrupted by two sandwich nanojunctions (Nb/Al–AlOx/Nb) having an area of about (300
$\times$
300) nm
²
. These nanodevices have been fabricated by means of a focused ion beam sculpting method, which is used as a lithographic technique to define the various elements of the SQUID. We have performed measurements of current–voltage, critical current–magnetic flux characteristics, and switching current distributions from the zero voltage state for different temperatures. The high critical current modulation depths and the low intrinsic dissipation exhibited by these devices ensure a suitable sensitivity for nanoscale applications in the whole temperature range investigated.