Abstract: In a single crystal growing technique (crystal pulling) a method for minimizing impurity contamination and preventing heat convection currents from affecting the solid-melt crystal growing interface which uses a floating baffle plate in the interior of the feed melt containing crucible in order to obtain a single crystal of a compound semiconductor having a high melting point and exhibiting a high dissociation pressure at said melting point such as a compound semiconductor of Groups III-V, especially GaAs or Gap, the crystal having a small dislocation density. Improvement is made on the shape of the baffle plate and on baffle plate control mechanisms, and this baffle plate is combined with selected intra-furnace pressure or heating mechanisms or temperature measuring mechanisms.

Abstract: In a single crystal growing technique (crystal pulling) a method and apparatus for minimizing impurity contamination and preventing heat convection currents from affecting the solid-melt crystal growing interface which uses a floating baffle plate in the interior of the feed melt containing crucible in order to obtain a single crystal of a compound semiconductor having a high melting point and exhibiting a high dissociation pressure at the said melting point such as a compound semiconductor of Groups III-V, especially GaAs or Gap, the crystal having a small dislocation density. Improvement is made on the shape of the baffle plate and on baffle plate control means, and this baffle plate is combined with selected intra-furnace pressure or heating means or temperature measuring means.

Abstract: In pulling a single crystal of a compound semiconductor having a high melting point and exhibiting a high dissociation pressure at such melting point, like a compound semiconductor of elements of Groups III-V such as GaAs or GaP, from a feed melt contained in a crucible and subject to an inert gas atmosphere of a high pressure, apparatus for positioning a baffle plate floating in the feed melt in a predetermined position in a stable state in order to prevent heat convection of the feed melt in the crucible from affecting the solid-melt interface and consequently a single crystal having a small dislocation density can be obtained.

Abstract: In a high pressure vessel such as an electric furnace using an inert gas of an extremely high pressure as an atmosphere for preventing the evaporation of arsenic or phosphorus when pulling a single crystal of a compound semiconductor having a high melting point and exhibiting a high dissociation pressure at the melting point, such as a III-V Group compound semiconductor, e.g. GaAs or GaP from a feed melt contained in a crucible, it is intended to rotate and vertically move a crucible supporting shaft and a single crystal pulling shaft smoothly without impairing at all the gas-tightness in the furnace, the drive means utilizing a magnetic force for performing such rotational and vertical movements.

Abstract: In the suspension polymerization in an aqueous medium of vinyl chloride alone or of a monomer mixture comprising vinyl chloride as a major component and other monomers copolymerizable therewith as a minor component, depositin of polymer scales on the inside surfaces of the polymerization vessel is surprisingly prevented by coating the interior surface of the vessel and auxiliary equipment prior to the polymerization with at least one compound selected from the group consisting of hydroxyhydroquinone and pyrogallol.