THERMOELECTRIC STUDY OF Y-BA-CU-O THIN-FILM ON MGO SUBSTRATE PREPAREDBY RESISTIVE EVAPORATION

Thermoelectric measurements were carried out on Y-Ba-Cu-O thin film de posited on MgO substrate by resistive evaporation technique. A pulveri zed mixture of Y, BaF2 and Cu weighed in the atomic proportion was eva porated from resistively heated source onto a MgO substrate kept at 40 0-degrees-C using a simple vacuum system. The substrate temperature wa s then raised to 700-degrees-C for insitu heat treatment. Oxygen was i njected through a nozzle placed close to subtrate surface, thus raisin g the pressure to about 7 Pa during the heat treatment, which lasted f or about 15 minutes. The film was then gradually cooled down to room t emperature and the pressure raised to atmospheric pressure. The films thus obtained were measured and the values of thermoelectric power mea surements in the plane of the film were found to be close to the typic al thermoelectric power values of crystalline Y-Ba-Cu-O superconductor s. As expected, vanishing values of the thermoelectric power have been observed below 80 K. If the relation observed for sintered Y-Ba-Cu-O is applied for thin films, it suggests an extremely low oxygen deficie ncy.