Fabrication and Characterization of Single-Electron Transistors Based on Al/AlOx/Al and Nb/AlOx/Nb Tunnel Junctions

The SAIL (self-aligned in-line) technique has been applied to the preparation of ultrasmall metallic tunnel junctions. By using e-beam lithography and sputter methods the area of both Al/AlOx/Al and Nb/AlOx/Nb contacts has so far been reduced to less than 0.005µm2. At low temperatures high-ohmic double junctions with a small metallic island in between show the Coulomb blockade effect. The current through such a device can be modulated by a voltage applied to a gate electrode capacitively coupled to the island (single-electron transistor). Both these single-charge phenomena have been observed at temperatures of a few hundred mK