Coulomb blockade effects in anodised niobium nanostructures

TL;DR

This study investigates Coulomb blockade phenomena in anodised niobium nanostructures, demonstrating control over their electrical behavior and potential for tunable single-electron devices.

Contribution

It introduces a fabrication method for niobium nanostructures with tunable Coulomb blockade effects and demonstrates gate modulation of their electrical properties.

Findings

Coulomb blockade observed in samples with resistance >6 kΩ/sq

Electrical behavior depends on room temperature sheet resistance

Gate voltage can modulate current-voltage characteristics

Abstract

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