Masahiro Tahashi

Crystal orientation of non-magnetic materials by imposition of a high magnetic field

Abstract From the view point of learning from the nature, the controlling of crystal orientation is accounted to be a major subject for materials processing. This paper reviews the researches on the crystal orientation by use of a high magnetic fieldand belongs to the category of researches for mimicking structures, namely the crystal orientation, which nature or livingbodies are forming. Regarding to the crystal orientation, several methods such as unidirectional solidification and epitaxial growth and so on have been developed hitherto. On the other hand the magnetization force that is familiar with the force to attract iron to a magnet, has been recognized to be effective even in non-magnetic materials when those are placed under a high magnetic field, which has become rather conveniently available by developing superconducting technologies in these days. In this paper, main results obtained when the imposition of a high magnetic field was accompanied to several materials processing such as electrodeposition, vaperdeposition, solidification, baking, slip-casting and precipitation, arereviewed from the view point of crystal orientation of non-magnetic materials.

Antimony Treatment Effect on Cd1-xMnxTe Growth on GaAs by Metal-Organic Vapor Phase Epitaxy

A heteroepitaxial film of Cd1-xMnxTe has been grown on a (100)GaAs substrate by metal-organic vapor phase epitaxy. It is shown that a high quality Cd1-xMnxTe film can be grown on the GaAs substrate by pretreating the GaAs substrate with triethyl antimony at 650°C. The best full width at half maximum of the X-ray diffraction peak of the Cd1-xMnxTe film (x=0.12) obtained was 650 arc sec. The effects of the triethyl antimony on the film quality of Cd1-xMnxTe are discussed.

Growth and Characterization of Vanadium-Doped ZnSe by Metalorganic Vapor Phase Epitaxy

Vanadium-doped ZnSe was epitaxially grown on a (100) GaAs substrate by metalorganic vapor phase epitaxy under atmospheric pressure. The effects of the molar supply ratio of dimethylzinc to dimethylselenide on crystallinity were investigated to determine the optimum vanadium doping conditions. In the present study, as dopant sources of vanadium, vanadocene and triethoxyvanadyl were used. When triethoxyvanadyl was used as a dopant source, the crystal growth condition of vanadium-doped ZnSe changed from epitaxial growth to polycrystal growth at a molar supply ratio between 1.2 and 1.5. The magnetic property of vanadium-doped ZnSe fabricated at a molar supply ratio of 1.2 was measured using a superconducting quantum interface device at room temperature.

Crystal growth of vanadium-doped ZnSe using triethoxyvanadyl by metal-organic vapor phase epitaxy

As a new diluted magnetic semiconductor, vanadium-doped ZnSe is theoretically predicted to induce ferromagnetism above room temperature without carrier doping. Vanadium-doped ZnSe was epitaxially grown on (100) GaAs substrate by metal-organic vapor phase epitaxial method in an atmospheric pressure. As a dopant source of vanadium, triethoxyvanadyl was used. The influences of molar supply ratio of dimethylzinc to dimethylselenide on crystallinity were investigated in order to research the optimum vanadium-doping condition. The crystal growth condition of vanadium-doped ZnSe changed from epitaxial growth to polycrystal growth at molar supply ratio between 1.2 and 1.5.

Electrical Conduction of Composites of Tin Oxide and Zinc Oxide in Hydrogen

A composite of tin oxide and zinc oxide was examined for possible application as a hydrogen gas sensor. The conduction mechanism of the composite was investigated in an atmosphere of hydrogen and air. For the composite, the temperature dependence of electric resistance suggests that the conduction mechanism in air differs from that in hydrogen. The electrical conduction in hydrogen was predominated by the hopping between tin dioxide grains and that in air was predominated by the conduction at the zinc oxide grain interface. The sensitivity of the composite to hydrogen gas was maximum at 460 K. The mechanical property of the specimen estimated from fracture strength was improved by adding zinc oxide to the composite.