Fabrication and measurement of metallic single electron transistors

Using the so-called self-aligned in-line technique, we have fabricated sing le electron transistors based on the metals aluminum. tantalum and chromium . The material deposition was carried out without exception by sputtering. The samples were electrically characterized both in a dilution refrigerator and in a helium-3 cryostat. In case of transistors made completely of (sup erconducting) aluminum we observed in the modulation characteristics deviat ions from the predictions of the orthodox theory of sequential quasiparticl e tunneling. They are caused by additional current contributions due to Jos ephson-quasiparticle cycles. Furthermore, we report on the low-temperature behavior of mixed single electron transistors made of tantalum and chromium islands, respectively, between aluminum oxide barriers and external alumin um electrodes.