Fabrication of MgB2 nanobridge dc SQUIDs by focused ion beam

摘要: Abstract We have studied fabrication of MgB2 intragrain nanobridge dc SQUIDs by a focused ion beam (FIB) patterning technique. Not only the nanobridges as Josephson elements but SQUID loop was patterned FIB. The voltage 30 kV and current 0.9 nA for 1.5 pA nanobridges. Each bridge had nominal width length about 100 nm thickness 650 nm. 3 μm × 3 μm hole with 2 μm average linewidth. zero-field superconducting transition temperature (Tc) 37 K. Current–voltage (I–V) characteristics showed large excess currents at all temperatures small portion resistively-shunted-junction (RSJ) component which increases approaches Tc. At low temperatures, I–V curves exhibit heating effect second step, is believed to be due grain boundary near nanobridge. well-behaving modulation properties depth more than 30 μV 33.5 K 110 μV 15 K. These results together our previous on intergrain suggest that based FIB-patterned highly tolerant conditions.