Bismuth-telluride films prepared by vacuum-arc plasma method for thermoelectrical transducers

The results of using (BiSb)/sub 2/Te/sub 3/ and Bi/sub 2/(TeSe)/sub 3/ films prepared by pulsed vacuum plasma method in contactless thin-film TETs are presented. The devices are compatible in technology and miniaturization degree with microelectronic structures and, hence, can be used as components of special-purpose integrated devices for converting, processing and measuring of electrical signals. Comparison is made between the parameters of two types of differential transducers of identical design with thermobattery branches made of PbTe/GeTe films (reference device) and (BiSb)/sub 2/Te/sub 3//Bi/sub 2/(TeSe)/sub 3/ films, respectively. The films were deposited by flash evaporation and pulsed plasma methods onto anodic Al/sub 2/O/sub 3/ wafers used as a base for the device. It is found that the bismuth-telluride TET shows a much higher conversion coefficient as compared to the reference device. Thus, the conversion coefficient increases from 6 to 12 V/W in case of plasma method and from 6 to 8V/W in case of flash evaporation. The conversion coefficient can be further increased by annealing (BiSb)/sub 2/Te/sub 3//Bi/sub 2/(TeSe)/sub 3/ branches in argon. The transducer works at 5-10/sup 5/ /spl mu/W input power and 0-100MHz input frequency, with the conversion error <1.5%. Another advantage of the (BiSb)/sub 2/Te/sub 3//Bi/sub 2/(TeSe)/sub 3/ TETs is that there is no need for protective film on the branch surface against degradation of device parameters normally found with PbTe/GeTe-based devices due to branch material oxidation. It should also be noted that lower surface resistance of branches subjected to annealing allows formation of thermosensitive elements with lower output resistance on the same wafer area. Besides, for the same rating values of thermosensitive elements, smaller area of dielectric wafer is required and the overall sensor size is smaller.