A brief account is given of a sputtering technique for thin film deposition of ZnO and design parameters of the layered structures including ZnO/glass, ZnO/Si, ZnO/sapphire for making ZnO thin film surface acoustic wave (SAW) filters. An rf-spherical sputtering system is used for making thin films of c-axis oriented ZnO on glass or Si, i.e. (0001) ZnO/glass and (0001) ZnO/Si structure. A planar magnetron is used for making thin films of single crystal ZnO on sapphire, i.e. (0001) ZnO/ (0001) sapphire and (11_??_0) ZnO/ (01_??_2) sapphire. High temperature stability with temperature coefficient of frequency <10 ppm/°C, is obtained with the 0th mode of Rayleigh wave on the (0001) ZnO/glass structure. High effective coupling coefficient, k2_??_4_??_5%, is obtained with the 1st mode of Rayleigh wave, Sezawa mode, on the (11_??_0)ZnO/(01_??_2) sapphire structure. The former structure is used for making SAW Nyquist filters for TV sets and demodulators for TV station. The latter is available for making GHz SAW filters for communication systems.
This paper describes the spatial response of a monolithic array transducer and a trial real-time ultrasonic receiving system made by combining such a transducer with an electronical data acquisition system. It is concluded from the experiment that the point spread function is mainly contributed by the diffusely-propagating longitudinal waves rather than the resonant plate waves and the location of maximum intensity corresponding to the oblique incidence is only shifted very little from that obeying Snell's law. The latter is due to the directivity of the receiving response, depending on the electrode width of the transducer. In the trial receiving system, described here the data sampling technique with a variable speed decreased the influence of electronical switching spikes for data selection to a remarkable extent. In the special case of slow sampling, the displayed picture is slower than the actual movement but follows its movement without flickering.
A functional form of the psychrometric formula has been derived by a model of an infinitely broad flat evaporating surface. The model of an infinitely long cylindrical evaporating surface introduced in this report has been found to be well adapted for deriving the functional form of the formula. The conventional theory of the Sprung's psychrometric formula has been developed on the assumption that the air through the wet part of the psychrometer is completely cooled to the wet bulb temperature and completely saturated by water vapor. The results of experiments with two psychrometers of the graft thermometer type show that the above mentioned assumption are not realized.
Optimum conditions for measuring the minority carrier in semicondector wafers (Si), using a contactless photoconductive decay method were examined. The analysis ontains wafer factors detetmined by the characteristics of semiconductor wafers and external factors determined by a contactless measurement system. The influence of wafer factors, namely, bulk lifetime (τb) surface recombination velocity (s), wafer tihckness (W), resistivity (ρ) and diffusion coefficient (D) are analyzed. While the influence of externel factors, namely, absorption coefficient (α) and pulse width are analyzed under a condition where the microwave frequency is 10 GHz. As a result of the present study it is found, for instance, in case of the measuremnt of recombination rate near a surface of a wafer, W, τb and α should be large and the incidence surface of microwaves should be the same as the illuminate surface. Experimental results for various values of wafer thickness and pulse width correspond qualitatively well to the calculated results.
Information on the wind profile in the upper atmosphere is important for a wide range of meteorological, air pollution mesurements etc. Remote sensing has frequently been used for this purpose. This paper describes a new two-dimensional spatial correlation method using laser radar techniques in which sequentially measured planar aerosol patterns are correlated. This method has advantages over other remote sensing techniques in that spatial wind information can be obtained and measurement can be made using aerosol suspended in the atmosphere as a tracer. Fundamental measurements were made to show the feasibility of this method. A cloud was selected as a tracer. The results show that the maximum correlation factor is more than 0.88 which indicates that the correlation is very stable and that this method can be used with high reliability.
The characteristics of an αNPO (donor)-BBOT (acceptor) energy transfer dye laser pumped by a N2 laser are presented. In the ETDL system, the laser power of sensitized BBOT dye depends on the donor concentration and becomes a few times larger than that of BBOT alone. Large blue shifts in the lasing wavelength of the sensitized one occure at a higher concentraitons of the donor. The rate constants of the energy transfer are also estimated.
The synthesis of chemical compounds by high fiuence implantation of energetic ions attracts notice as a new application of the ion implantation technique. The chemcal activity and the high energy of implanted ions make possible to produce atomic mixture of controlled composition without thermodynamic constraints. It reduces, on the one hand, the synthesis temperature of compounds, which in turn reduces the auto-doping of impurities that is unavoidable in cases of growth of compound crystals with high melting point. On the other hand, it makes possible to produce new metastable phases of composition, for example, improved superconductors of nonequilibrium compositions. This paper describes mainly the synthesis of silicon compounds-SiO2, Si3N4 and SiC-which are of wide application to material technique and electronic devices, and shows that properties comparable to or better than those of thermally grown compounds can be obtained. It refers also to the application of the synthesized compounds.
Preparation techniques and various properties of plasma-assisted chemical vapor deposition (CVD) films are reviewed. This technology has been actively investigated on account of potential applications of low temperature deposition. Especially, silicon nitride films are useful as a passivation film of integrated circuits and amorphous silicon films are expected as a solar cell material. Emphasis in this review is placed on a fundamental understanding on plasma CVD. With this end in view, the interrelations of deposition conditions, composition and bond structure of atoms in the films, physical and electrical properties of the films, and device characteristics are summarized for silicon nitride and amorphous silicon films.