Coulomb blockade effects in anodized niobium nanostructures

Niobium thin film wires were fabricated using electron beam lithography with a four layer lift-off mask system, and subsequently thinned by anodization. The resistance along the wire was monitored in situ and trimmed by controlling the anodization voltage. Depending on the room temperature sheet resistance, samples showed either superconducting or insulating behaviour at low temperatures. The Coulomb blockade was observed for samples exceeding 6 kiloohms per square. Samples were also made in a single electron transistor-like geometry with two weak links made by combined angular evaporation and anodization. Their current-voltage characteristics could be modulated by a voltage applied to an overlapping gate. (author)