Tadatosi Hibi

On the Metallic Shadow‐Casting Using a Nozzle System

A new device for metallic shadow‐casting by using the nozzle system is proposed, and an outline of the apparatus is given. The present device has a shutter, a nozzle, and a cover plate between specimen and filament in addition to the usual apparatus. The dimensions of the nozzle were chosen from the maximum of 3‐mm diam, 1.5‐mm diam, and 22 mm to the minimum 1.5‐mm diam, 0.7‐mm diam, and 38 mm as diameter at the entrance, diameter at the exit, and the length, respectively. It was found that this method was not only conspicuously effective in obtaining much more accurate shadows than that obtained by the usual method with the same shadowing material, but also brought into possible use metals, as shadowing materials, which could not be used for such a purpose by the usual method. Shadowing qualities of many kinds of evaporated metals are compared and a new rule for the order of aggregation of deposited metallic thin films is also proposed.

DIRECT OBSERVATION OF CRYSTAL IMPERFECTIONS INTRODUCED BY WEAK ELECTRON IRRADIATION IN WATER-ETCHED KCl SINGLE CRYSTAL

The changes in a water-etched KCl single crystals due to weak electron irradiation were observed by means of an electron microscope and by electron diffraction. It was found that in a crystal, the thickness of which became large with the distance from the edge, dislocation loops appeared and their development as observable. When the change of the thickness of the crystal is pronounced, it was easy to find large dislocation loops in the thin part close to the edge of the crystal. In the case in which the size of a dislocation loop is less than 0.5 µ in diameter, one dislocation loop changed abruptly into one void with weak electron irradiation. However, a larger dislocation loop changed into one void and several small dislocation loops. Interactions between two crystal imperfections were also observed in this experiment. From the experimental results, the mechanism of coagulation or dispersion of vacancies in water-etched KCl crystals under weak electron irradiation is discussed.

Direct Observation of Crystal Imperfections in KCl Single Crystal by Electron Microscope

The processes of change of a thin KCl single crystal due to electron irradiation were observed by means of an electron microscope and electron diffraction. It was found that under weak electron irradiation loop structures first appeared and then disappeared showing a lot of small bright specks over the whole crystal. In this stage, each diffraction spot had streaks in 〈100〉 directions. Under intense electron irradiation bright squares appeared initially without the appearance of loop structures. In this stage, the diffraction pattern was a perfect net‐like pattern. It was found that by using the replica technique, loop structures and large squares appeared in the crystal, and also that by using the dark‐field image method the contrast of loop structures and bright squares was due to Bragg reflection, which had resulted from the formation of voids and cubic cavities in the crystal, respectively. From the experimental results, the mechanism of coagulation of vacancies in KCl crystal with electron irradiatio...

Successive Electronmicroscopic Observation of Coloured and Bleached KCl Crystal

The surface changes in a given part of the same KCl crystal during colouration by X-rays and in the process of bleaching by natural light have been successively observed by using two-stage replica. A slightly modified Bradleys method was used for making two-stage replica. By this method, the surface change at the definite position of the same KCl crystal was observed successively. According to the present results, it has been clearly confirmed that crystallites grown on the KCl crystal during X-ray colouration disappear during bleaching through the process quite reverse to the crystal growth in colouration and that the behaviour of the crystal growth and its disappearance are not simple, but very peculiar. Results obtained have been briefly discussed.

Electronmicroscopic Observation of the Additively Coloured KCl Crystal

The KCl single crystal which was grown from the melt, thermally quenched, and additively coloured with potassium metal were observed electronmicroscopically using replica technique. Growth of crystallites was seen both on the outer surfaces and in the interior of the crystal when it was thermally quenched or it was coloured additively. The crystallites grew more markedly in the latter case than in the former. The mechanism by which F centres are formed were considered.

New Method for Preparing Unusually Oriented Tungsten Tips and Their Growth Mechanism

A new method for preparing tungsten tips having an unusual orientation, for example, the [100]- or the [111]-orientation, was studied by using a field emission microscope. It was found that tungsten tips having the [100]- or the [111]-orientation could be obtained with heat treatment of the tip at low temperature (1500°–2300°K) after introducing air or oxygen into the experimental tube. To make clear the mechanism of the change in the tip orientation from the normal orientation to the unusual one, light- and electron-microscopic observations of the cathodes were carried out. As a result, it became clear that the growth mechanism of the unusual tip could be explained by assuming that the tungsten tip rotated around a fixed -axis under the tungsten carbide film so as to transfer to the stable state from a semi-stable state.

High‐Resolution Replicas and Their Application

Using methyl methacrylate as an intermediate, an attempt was made to obtain a high‐resolution two‐step replica, by improving evaporation elements and evaporation method. It was found that, by using Zr, Si, and Fe, with Ge and Cr as evaporation elements, the resolution of two‐step replicas was superior to that obtained up to the present. It is also known that the resolution of replicas obtained by performing metallic evaporation after treatment by ion or electron bombardment for a methyl methacrylate intermediate replica is superior to that without bombardment. Two evaporation methods—the usual continuous method and an intermittent one—were compared. A new method for the production of surface replicas of microspecimens is also proposed. The high‐resolution replica obtained here is compared with others along with a brief consideration of the results obtained.

Electronmicroscopic Observation of Print-Out Effect on AgBr Microcrystals

By using silver bromide microcrystals obtained from a high sensitive photographic film emulsion, the effects of the intensity of light source and the temperature of the specimen on the print-out effect of the silver bromide crystals were studied electron-microscopically. As a result, it was found that with increasing the intensity of light source or with raising the temperature of the specimen the density of the pits decreased and well-defined tri-pyramidal pits began to appear on the surface of the grain. Although triangular patterns were observed frequently on the surface of the grain at room temperature for weak light illumination, they decreased in number and became large in size with increasing the intensity of light source or with raising the temperature of the specimen. The protrusion and whisker of silver also appeared on the grain at an elevated temperature due to light illumination. Experimental results obtained are discussed.

A Note on the Shape of Cathode Tip in the Field Emission Microscope

Successive changes in the shape of field emission nickel cathode tips resulting from two types of treatment–simple heat-treatment and heat-treatment with continuous application of 5000 V–were observed. As the results, it was found that in the former case the rate of decrease in length is more pronounced than that in thickness, while in the latter case the tip becomes thinner nearly uniformly over the entire surface until the tip becomes of certain thickness. Also it has been clarified that heat-treatment with continuously applied anode voltage is necessary to obtain a good tip.

Angular Dependence of the Apparent Work Function of Carbon-Adsorbed Tungsten Tip

Unusually oriented carbon-adsorbed tungsten tips are made by a method developed by the present authors. Changes of the apparent work function and of the emission current on several crystal planes of these tips are measured in a F.E.M. tube as a function of angular distance from its apex. It is found that the work functions of the crystal planes become small in order of {110}, {100}, {221} and {210}, and also that the change in the apparent work function with the increase in angular distance becomes pronounced in this order. The crystal plane having smaller work function is found to show more pronounced decrease of emission current with the increase of angular distance from the apex compared with the crystal plane having larger work function.