The general review of the molecular beam epitaxy method which has been developed in recent years is given with its promising applications for electronic devices. At first the interaction kinetics such as adsorption and hopping processes of a molecular beam with a surface of solids are described briefly. The methods of generation and detection of the mole-cular beams are also described. The molecular beam epitaxy method used for the semi-conducting compounds like GaAs and AlxGa1-xAs is reviewed from the viewpoints of the experimental arrangement, crystal growth process, crystal properties, impurity-doping methods, and the electrical and optical properties of the resulting grown layers.
Crystal growth of Pb1-xSnxTe and Hg1-xCdxTe of most interesting narrow gap semi-conductors are reviewed. Problems arising in growth of the crystals, especially with an energy gap of about 0.1 eV, are pointed out and various methods are discussed to solve them. Differences in advantages between growth methods generally used are also shown, containing Bridgeman, Czochoralski, vapor transport, liquid epitaxial and vacuum evaporation growth techniques.
By adequate pyrolysis, polyacrylonitrile is turned into a semiconductor at 500_??_600°C, resulting from the formation of conjugated double bonds throughout the specimen. In this paper, therefore, the specimen is prepared under the condition of slightly imperfect pyrolysis in order to study the effects of the preparation on the electrical properties of the specimen. At first, the measurements of frequency characteristics of its impedance are carried out at several ambient temperatures. An equivalent circuit of adequate form is then obtained for them, and the meaning of each branch is discussed. Concerning the part corresponding to imperfectly conjugated double bonds at the surface region, the impedance is remarkably affected by the ambient temperature. As the temperature rises, for example, a part of its capacitive element seems to be turned into a conductive one by reason of a certain change in structure.
The polymerization of acrylamide in aqueous solution was carried out with β-irradiation facilities using unsealed 85Kr gas as an internal radiation source. The effects of various factors on the degree of polymerization, as well as the molecular weight distribution were studied. The experimental results are compared with the results using γ-rays from a 137Cs source. Some of the results obtained are as follows. (1) The degree of polymerization, for either source, is inversely as the 0.27th power of dose rate and proportional to the 1st power of monomer concentration. (2) In addition, the temperature dependence of the degree of polymerization shows a similar tendency. (3) On the other hand, for the molecular weight distribution, a slight difference is observed.
Vickers microhardness (Hv) and density (ρ) of silica films 2_??_10μm thick evaporated from SiO in vacuum at 1×10-3 torr on so-me plastics and commercial glass substrates were determined. Irrespective of substrates materials, the microhardness of silica film at 25g loading was found to give Hv=87±8kg/mm2, and the film density to be ρ=1.64±0.1g/cm3. Electron diffraction analysis and infrared spectroscopy of the film showed the film structure to be amorphous and the film composition Si2O3.