Proximity effect thermometer for local electron temperature measurements on mesoscopic samples

Using the strong temperature-dependent resistance of a normal metal wire in proximity to a superconductor, we have been able to measure the local temp erature of electrons heated by flowing a direct-current (dc) in a metallic wire to within a few tens of millikelvin at low temperatures. By placing tw o such thermometers at different parts of a sample, we have been able to me asure the temperature difference induced by a dc flowing in the samples. Th is technique may provide a flexible means of making quantitative thermal an d thermoelectric measurements on mesoscopic metallic samples. (C) 1999 Amer ican Institute of Physics. [S0003-6951(99)04648-3].