IN-SITU SURVEY SYSTEM OF RESISTIVE AND THERMOELECTRIC PROPERTIES OF EITHER PURE OR MIXED MATERIALS IN THIN-FILMS EVAPORATED UNDER ULTRA-HIGH-VACUUM

The study of thermoelectric and resistive in situ behaviours depending on temperature for thin films of either pure or composite materials o btained under ultra-high vacuum, is very interesting, since they can b e used as strain gauges or superficial resistances. However, studies b ecome particularly difficult when the measurements generate very low-l evel electrical signals. Indeed, these turn out to be hardly detectabl e because of the perturbations brought by the experimental environment . The apparatus described below allows for the measurement of resistan ce with a relative uncertainty of 2 x 10(-4), resistance variation wit h an absolute uncertainty of 2 m Omega and thermoelectric e.m.f. of ab out 2 mu V Films studied in the laboratory generally exhibit resistanc es lower than 100 Omega and resistance variations due to temperature v ariations of about a few ohms. So this device has sufficient technical characteristics for our studies. It can be connected to a PC, which a llows for easy data collection and treatment.