2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/22688We have developed a fabrication process for nanoscale tunnel junctions which includes focused-ion-beam etching from different directions. By applying the process to a Nb/(Al-)Al_2O_3/Nb trilayer, we have fabricated a Nb single-electron transistor (SET), and characterized the SET at low temperatures, T=0.04-40 K. The superconducting gap energy and the transition temperature of the Nb SET agree with the bulk values, which suggests high quality Nb junctions. The single-electron charging energy of the SET is estimated to be larger than 1 K.Published version, RevTeX4Mesoscale and Nanoscale PhysicsMaterials Sciencetext