Recently, studies on impurity doping onto a crystal surface by ion bombardment has developed rapidly as problems of interaction between molecular or ion beams and crystal surfaces. A historical survey on ion bombardment of crystals, a variety of mechanisms to introduce impurities into crystal lattices, and also fabricating methods of semiconductor devices which were made using beam technology are reviewed. This doping method is providing a new field both in fundamental research in crystal physics and application to semiconductor technology.
The characteristics of a thermoluminescent dosimeter of fluorite crystals was investigated by a method in which a charge-sensitive amplifier was used. The reading system of this method is to integrate the intensity of emission glow under the required peaks. The data for zinc fluorite doped with manganese and for lithium fluorite have been obtained as the basic data of thermoluminescence dosimetry covering the range of x-ray exposure dose from 10-1 to 103 roentgen.
The arrangement and characteristics of the x-gamma ray coincidence-counting system and the method of standardizing the disintegration rate of 88Y and 54Mn sources were previously reported. In the present paper, the absolute disintegration rate of a 55Fe source is determined by modifying the x-gamma ray coincidence-counting method. The absolute disintegration rate of a 55Fe source emitting only x-rays has, ordinarily, been measured by the 4πX counting method. In this report, the calibration of a 55Fe source by the x-gamma ray coincidence method is attempted. The prin-e ciple of this idea is as follows: a known amount of 57Co or 54Mn isotope, which emitts both x- and gamma-rays, is added to a 55Fe source separately, the radioactivity of each mixed source is counted with x-gamma ray coincidence equipment, and then the absolute disintegration rate of the 55Fe isotope is calculated by analyzing the counting results, The 55Fe solution used in this experiment was a standard solution supplied by Radio-Chemical Center (U. K.). The 57Co and 54Mn isotopes, were produced by irradiating highly-pure nickel sheet with a high energy gamma ray beam from the linac at JAERI, and by irradiating electrolytic iron with fast neutrons in JRR-3, respectively. The absolute disintegration rates of 57Co and 54Mn sources were well defined by the x-gamma ray coincidence method decribed in previous papers, and then either 57Co or 54Mn master solution was, mixed with the standard solution of 55Fe. The counting sources were prepared by dropping and evaporating the solution on a thin mylar film, and the radioactivity of these sources were measured with the x-gamma ray coincidence counting system. It is found that the agreement between 57Co. and 54Mn tracer method of absolute counting for 55Fe was good.
A photoelectric comparator which automatically finds and measures locations of density maxima on a spectrum plate is described. A part of the projected image of the spectrum is oscillated by means of a rotating glass plate in front of the slit-detector assembly, while the photographic plate is slowly moved by a lead screw. The principle of determining the positions of density peaks is based on a coincidence method between two pulses, one of which is a peak pulse gene-rated by successive differentiation of the photoelectric output of the detector and the other is a fiducial pulse synchronized with the rotating scanner. The locations of spectral lines are displayed with a digital scaler and printer actuated by the coincidence pulses. The accuracy of the instru-ment, which is nearly one micron for regular runs, is better than that of the conventional type of comparator. This instrument is a particularly powerful tool in the field of spectrochemical analysis.
A method for vacuum-arc evaporation has been developed. This uses arcs in a vacuum bet-ween two electrodes made of the evaporant and supplied with an alternating voltage of 10_??_50 volts, and can easily be applied to evaporate all kinds of conductive materials. For the purpose of structural study of thin films of highly-refractory metals, an apparatus was constructed in which the evaporation rate reaches as high as 103Å per sec. and substrates can be heated up to 1600°C. Detaild description of the apparatus is given. Studies by the use of electron microscopy and ele-ctron diffraction are also described, especially in the cases of depositing molybdenum and tungsten on cleavage surfaces of rock salt, on carbon films and on cleavage surfaces of graphite at various temperatures. Carbide formation was found to occur as a result of a direct reaction of the depo-sited metals with carbon in the, case of carbon and graphite substrates