  Three types of metallic nanostructures comprising niobium were investigated
experimentally; in all three types, electric transport at very low temperatures
was governed by Coulomb blockade effects.
  1. Thin film strips of niobium could be tuned into resistor strips by an
electrochemical anodisation process, using microfabricated masks and in situ
resistance monitoring. These resistors showed a transition from superconducting
to insulating behaviour with increasing sheet resistance, occurring at a value
approximately equal to the quantum resistance for Cooper pairs, h/(4e^2).
  2. Combining the anodisation technique with lateral size minimisation by
shadow evaporation, devices in a single electron transistor-like configuration
with two weak links and a small island between these were made. Direct evidence
for the Coulomb blockade in the anodisation thinned niobium films was found
when the transport characteristics could be modulated periodically by sweeping
the voltage applied to a gate electrode placed on top of the structure.
  3. Conventional single electron transistors with Al base electrodes, AlO_x
barriers formed in situ by oxidation, and Nb top electrodes were made by
angular evaporation. The output current noise of such a transistor was measured
as a function of bias voltage, gate voltage, and temperature. The low frequency
noise was found to be dominated by charge input noise. The dependence of the
noise on the bias voltage is consistent with self-heating of the transistor
activating the noise sources.
