The four-point probe method is most adequate for resistivity measurement of semiconducting materials. However, in measuring a vapor-deposited semiconductor film on substrate of the same material, the effect of substrate parameters on measured value must be considered. In the case of N on P or P on N material, the p-n junction between film and substrate has been assumed as an insulator. In this paper, the effect of substrate parameters on the current and potential distribution in the film is calculated and it is shown that the measured value of the re-sistivity is a product of film resistivity and a function of substrate parameters. A consideration of this potential distribution tells that the p-n junction between film and substrate does not always act as an insulator. In the case of N on N or P on P material, the measured value of resistivity is a function of substrate resistivity, film resistivity and film thickness, and this function is numerically calculated. With this function the film resistivity can be determined provided that the film thickness is not very small.
We are well aware of the fact that various types of non-linear system elements are widely used and the sensitivity of measurements is finally limited by random noise in most physical in-struments. More explicitly, when many correlative random physical processes are passed through non-linear circuit elements such as detectors or rectifiers and the output random fluctuations are considered, the probability variables defined over positive region are fundamental quantities in the statistical physical engineering. First, a general expression of multi-dimensional probability density distribution function in the form of orthogonal series such as statistical Hermite expansion is introduced. This probability expression is more general than the well-known expansion expression due to Gram Charlier, because it includes the latter one. Then, for the special case of interest when many correlative physical quantities fluctuating only probability in positive region as mentioned in the above are treated, an explicit representation of joint density function in the form of statistical Laguerre expansion series is also presented. Further, it has been pointed out that the latter method using a statistical Laguerre expansion is closely connected with the statistical Hermite expansion method under a squaring non-linear transformation. We must call our attention to the fact that the statistical meaning (i.e., the random property) is reflected in each expansion coefficient. Finally, the detailed experimental considerations enough to corroborate the above theories are given in the following two cases: (a) a squaring rectifier with non-Gaussian random excitation, (b) a non-squaring rectifier with Gaussian random excitation. The statistical method described in this paper is also applicable to other wide fields of mea-surement on the random phenomena, since the probability variables defined only in positive region are fundamental in applied physics.
Studies are made to find an appropriate working system of multichannel pulse height analyzer which is to be loaded on the Lambda rockets of Tokyo University for the measurement of energy spectrum and intensity of cosmic rays at high altitude. The analyzer consisting of a pulse height-to-time conversion type analog-digital converter, a ferrite core matrix memory unit and a read-out unit, is originally a transistorized laboratory-use analyzer, the circuit layout of which was improved to reduce its size and to obtain accurate functioning especially of read-out system. The read-out unit is of a digital pulse transmission type that can transmit at intervals of 2.56 sec three data, namely, the channel number (0-15, 0-31), cosmic ray count (0-255) and measuring time (about 2.5 sec) on one channel of telemetrical transmission system, the frequency response of which is 110 cycles per second. The system with which the read-out time is to become 1/2, 1/3, …… 1/n for the transmission channel number designed of 2, 3, ……, n respectively and the electronic data receiving scheme that covers the whole ranges of channel number and cosmic ray count are worked out. The above system was actually used for Lambda 2-2 and Lambda 3-1 rocket experiments made at Kagoshima Space Center in December, 1963, and July, 1964, with satisfactory results.
The negative resistance phenomenon of metal-insulator-metal diode is investigated experiment-ally with an Al-Al2O3-Au thin film composite. This residual effect, which is characteristic of the negative diode, is shown to be caused by a particular state of conduction, subjected to temperature and applied voltage. The “voltage memory effect” is also shown on the voltage-current curve of the negative diode. Between 0.1_??_3.0c/s of frequency, the negative resistance is dispersive, and beyond 3.0c/s, the diode shows no longer the negative resistance. The exact mechanism of the negative resistance remains still unexplored.
For the purpose of measuring telemetrically the depth of snowfall, a gauge with photocells is devised, and studies are made on the measuring method to comply with the circumstantial con-ditions. The gauge is a cylindrical rod, 760mm in length and 35mm in diameter, in which 22 silicon photocells of size 5±5mm2 each are set at intervals of 25mm. It is provided with an ap-paratus for measuring the photocurrents. On the presumption that the attenuation of intensity of light penetrated through the laid snow is exponential, different methods of finding the depth are considered by which the depth can be estimated with ease if the error of a few centimeters is tolerated. In Appendix, details of the depth calculation and discussion on the structure of deeply laid snow are given.