Deep submicron Al-AlOx-Nb tunnel junctions and single electron transistors
with niobium islands were fabricated by electron beam gun shadow evaporation.
Using stencil masks consisting of the thermostable polymer polyethersulfone
(PES) and germanium, high quality niobium patterns with good superconducting
properties and a gap energy of up to 2Delta = 2.5 meV for the niobium were
achieved. The I(U) characteristics of the transistors show special features due
to tunneling of single Cooper pairs and significant gate modulation in both the
superconducting and the normal state.Comment: 4 pages, 4 figure