Gated circuits with two weak links, also known as electrometers or transistors, are sufficient to observe the charging effect corresponding to a single electron but more complex devices, referred to as turnstiles and single electron pumps, are required to accurately control the transfer of single electrons. Using facilities of IMS, electrometers were fabricated from metal lines as narrow as 50 nm, using a self-aligning double angle shadow evaporation technique. The devices were measured at temperatures between 4.2 K and 0.3 K in 4 He and 3 He cryostats using specially designed low-noise electronics. The electrometers clearly showed single electron charging effects, although an apparent gate modulation was observed, presumably caused by background charge fluctuations. The best electrometers had capacitances of about 0.2 fF per junction, with a gate capacitance of about 0.1 fF. Attempts at fabricating silicon-based SET devices have produced no working devices so far.
Work continues to improve the yield of our processes and to produce more complex devices.
More measurements are planned to understand the origin of the gate fluctuations and to improve on the design of the devices.