COULOMB-BLOCKADE EFFECTS IN ANODIZED NIOBIUM NANOSTRUCTURES

Niobium thin film wires were fabricated using electron beam lithograph y with a four layer lift-off mask system, and subsequently thinned by anodization. The resistance along the wire was monitored in situ and t rimmed by controlling the anodization voltage. Depending on the room t emperature sheet resistance, samples showed either superconducting or insulating behaviour at low temperatures. The Coulomb blockade was obs erved for samples exceeding 6 kiloohms per square. Samples were also m ade in a single electron transistor-like geometry with two weak links made by combined angular evaporation and anodization. Their current-vo ltage characteristics could be modulated by a voltage applied to an ov erlapping gate.