Measurement and control of the electronic temperature in small thin-film structures.

We discuss the thermal properties of small metal and insulating structures, interesting for bolometer applications. We report on the characterization of thin-film thermometers based on normal metalinsulator-superconductor tunnel junctions, operating at sub-Kelvin temperature and fabricated by using either niobium or aluminum as superconducting electrodes. The effect of different bias methods on the thermometer current-voltage characteristics is measured as well as the response of small metal structures to absorbed/removed power. The characterization is performed with a helium-3 refrigerator, compatible with the instrumentation generally available in ground or space-borne experiments. [ABSTRACT FROM AUTHOR]