A Comprehensive Overview of the Nanoscale SQUID-on-Tip Fabrication Process*

We present a comprehensive overview of the nanoscale SQUID-on-Tip (SOT) fabrication process as being implemented at University of Colorado Denver. A commercial pipette puller is used to draw down a 1 mm O.D. quartz glass capillary to diameters ranging from 85--150 nm. To create the room temperature (RT) electrical leads on the wide section of the pipette (i.e., the ``barrel"), 5 nm of Cr (adhesion promotion) and 50 nm of Au are deposited on opposite sides of the barrel via thermal vacuum deposition. The pipette is then rotated 90\(^\circ\) and masked so that a 250 \(\mu\)m strip of Au film, nominally 10 nm thick, is deposited between the superconducting (SC) leads thereby forming a shunt resistor. Indium is then soldered onto the Au leads to decrease the parasitic resistance of the Au film. Lastly, the SC Pb film is deposited in a cryogenic, ultra high vacuum chamber that reaches a base temperature of approximately 8 K. The tip opening, or apex, pointing directly at the source defines the zero-angle for deposition. The 25 nm SC leads are deposited at \(\pm 110^\circ\) with respect to the zero angle, and the final SC ring thickness varies from 15-20 nm. The SOT has a multitude of applications in scanning probe microscopy for materials research such as magnetic imaging and flux amelioration.