Electron cooling by arrays of submicron tunnel junctions

We cooled down the electrons of a 3 mu m(3) copper strip by using an on-chi p electronic microcooler made by a superconductor-insulator-normal-insulato r-superconductor (SINIS) structure. We obtained an electron temperature dro p Delta T similar or equal to-10 mK at a temperature of the bath slightly a bove T-b = 500 mK and we estimated a cooling power slightly larger than 20 pW at this temperature. In contrast to previous experiments, we obtained th is result operating with a simple 3 He refrigerator. The copper strip tempe rature change was sensed by measuring the voltage change across a current-b iased SINIS junction, with a temperature responsivity Delta V/Delta T simil ar or equal to-500 mu V/K. On-chip microcooler and thermometer have been fa bricated by two-angle shadow mask evaporation and e-beam lithography. (C) 1 999 American Institute of Physics. [S0021-8979(99)07206-0].