Recent investigations of new magnetostrictive materials and new type magnetostrictive transducers are reviewed. Firstly we described the magnetoelastic properties of Fe base amor-phous alloys, rare-earth iron alloys and magnetite which are new magnetostrictive materials. Secondly, new devices such as huge magnetostrictive transducer, magnetostriction type data tablet and magnetostrictive fast acting gas valve are explained.
ZnO piezoelectric films have been applied to ultrasonic devices for bulk acoustic waves as well as surface acoustic waves in VHF and UHF ranges, because ZnO has a low dielectric constant and a large electromechanical coupling factor among nonferroelectric crystals. In this paper, the present status of fabrication techniques of ZnO piezoelectric films, espe-cially sputtering techniques, is described. The dc diode sputtering system with side-positioned substrate developed in our country is compared with the conventional RF sputtering system with parallel-positioned substrate for obtaining well oriented ZnO films. Applications of the ZnO piezoelectric films to various ultrasonic devices such as ultrasonic transducers, composite resonators, concave transducers, SAW filters, SAW amplifiers, SAW convolvers, image scan-ners, SAW memories and surface acousto-optic devices are described. Among the devices, ZnO film SAW filters are expected to be employed in commercial TV sets in very near future.
The lattice expansion in the direction parallel to the film surface has been determined by X-ray diffraction for the two cases (1) as deposited and (2) after removal from the substrate, and the corresponding stress values ui and o'z have been calculated. Both a, and az are positive (tensile); δ2<1×109 dyn/cm2 for films thicker than 50nm, and (δ1-δ2)_??_1×109 dyn/cm2 for 50nm<d (film thickness)<a few hundred nm; a, and az, as well as the grain size, increase with d up to d, V150nm, above which they remain constant. Larger values of ai and as are observed if the deposition conditions are such that epitaxy is enhanced. The stress build-up. in films on the substrate can be explained according to the grain growth model. It appears, moreover, that the local tensile stress in free films, δ2, is balanced by a compressive stress in grain boundaries or surface layers.
An equivalent circuit and its impedance diagram are often useful for analysing the electrical characteristics of an organic semiconductor which consists of a series connection of different type layers. First in this report, a measuring element of pyrolyzed polyacrylonitrile semiconductor with a surface layer which was formed by electrolytic anode reaction in dilute hydrochloric acid was prepared, and its impedance was measured at frequencies from 30 Hz to l MHz under the influence of a DC bias. Then, the electrical conduction mechanism of the layer was discussed from the impedance diagram. In conclusion, in the higher field region the conduction across the layer seems to be mainly due to the Poole-Frenkel effect.
A number of suitable conditions for producing stable memory elements have been found in ZnS films with Al and Cu electrodes. Annealing at about 200 (°C) in 10-5 (Tory) was found to be very effective to stabilize the memory operations. Insertion of oxide layer between Al electrode and ZnS may improve the productive rate. Specimen exhibiting both memory operation and electroluminescence was also obtained.
A flat-plate Blumlein system was used to excite a molecular hydrogen laser in the vacuum-ultraviolet spectral region near 160nm. The fundamental characteristics of the rapid, high-power discharge pumping which is essential for vacuum-ultraviolet laser action are discussed using transient circuit theory. The laser spectrum and output energy were measured spectroscopically while varing the gas pressure and characteristic impedance of the transmission line. For operation of the molecular hydrogen laser, high values of the ratio of the applied electric field to gas pressure, E/p, (greater than 500 V/cm•Torr) are required and a transmission line with relatively high characteristic impedance of approximately 0.2Ω-m is preferred. From the measured dependence of laser line intensities on the hydrogen gas pressure, it is suggested that the upper laser leve is depopulated collisionally by high electron density, especially for those levels with relatively long radiative lifetime such as the (7-13) vibrational transition.