Acousto-Electric Effects in Cadmium Sulphide at Microwave Frequencies

[摘要] Acoustic amplifiers, operating at frequencies of 1GHz and above, have been constructed from hexagonal cadmium sulphide crystals. The main problem in making these devices was in obtaining efficient acousto-electric transducers for microwave frequencies. Evaporated thin films of CdS were used as transducers, and a close study was made of their properties, in order to obtain efficient generation of both shear and longitudinal acoustic waves, above 1 GHz. The transducers were deposited on heated substrates by direct vacuum evaporation of CdS crystals. X-ray analysis showed that under most deposition conditions, the films were polycrystalline, composed of hexagonal phase crystallites of CdS, preferentially oriented with their c-axes perpendicular to the substrate. The degree of structural order increased with film thickness, and. films under 0.5mu thick had a high degree of disorder. Acoustic waves were generated by applying an r.f. electric field perpendicular to the substrate, and parallel to the transducer thickness, so that normal films were thickness resonant longitudinal mode transducers. Evaporation at an oblique angle to the substrate, and at a deposition rate in excess of 0. 1u/min, caused the c-axes of the crystallites to tilt away from the normal, and grow towards the direction of evaporation. With the electric field normal to the substrate, and the c-axis at about 38.5

[发布机构] University:University of Glasgow

[关键词] Mechanical engineering, Electrical engineering