Provided is a self-supporting gallium nitride substrate useful as an alternative material for a gallium nitride single crystal substrate, which is inexpensive and also suitable for having a large area. This substrate is composed of a plate composed of gallium nitride-based single crystal grains, wherein the plate has a single crystal structure in the approximately normal direction. This substrate can be manufactured by a method comprising providing an oriented polycrystalline sintered body; forming a seed crystal layer composed of gallium nitride on the sintered body so that the seed crystal layer has crystal orientation mostly in conformity with the crystal orientation of the sintered body; forming a layer with a thickness of 20 m or greater composed of gallium nitride-based crystals on the seed crystal layer so that the layer has crystal orientation mostly in conformity with crystal orientation of the seed crystal layer; and removing the sintered body.

Provided is a self-supporting polycrystalline GaN substrate composed of GaN-based single crystal grains having a specific crystal orientation in a direction approximately normal to the substrate. The crystal orientations of individual GaN-based single crystal grains as determined from inverse pole figure mapping by EBSD analysis on the substrate surface are distributed with tilt angles from the specific crystal orientation, the average tilt angle being 1 to 10. There is also provided a light emitting device including the self-supporting substrate and a light emitting functional layer, which has at least one layer composed of semiconductor single crystal grains, the at least one layer having a single crystal structure in the direction approximately normal to the substrate. The present invention makes it possible to provide a self-supporting polycrystalline GaN substrate having a reduced defect density at the substrate surface, and to provide a light emitting device having a high luminous efficiency.

Provided is a self-supporting polycrystalline GaN substrate composed of GaN-based single crystal grains having a specific crystal orientation in a direction approximately normal to the substrate. The crystal orientations of individual GaN-based single crystal grains as determined from inverse pole figure mapping by EBSD analysis on the substrate surface are distributed with tilt angles from the specific crystal orientation, the average tilt angle being 1 to 10. There is also provided a light emitting device including the self-supporting substrate and a light emitting functional layer, which has at least one layer composed of semiconductor single crystal grains, the at least one layer having a single crystal structure in the direction approximately normal to the substrate. The present invention makes it possible to provide a self-supporting polycrystalline GaN substrate having a reduced defect density at the substrate surface, and to provide a light emitting device having a high luminous efficiency.

A seed crystal for SiC single-crystal growth includes a facet formation region containing a {0001}-plane uppermost portion and n (n>=3) planes provided enclosing the periphery of the facet formation region. The seed crystal for SiC single-crystal growth satisfies the relationships represented by formula (a): B.sup.k.sub.k-1<=cos.sup.1(sin(2.3 degrees)/sin C.sub.k), formula (b): B.sup.k.sub.k<=cos.sup.1(sin(2.3 degrees)/sin C.sub.k), and formula (c): min(C.sub.k)<=20 degrees. In the formulas, C.sub.k is an offset angle of a k-th plane, B.sup.k.sub.k-1 is an angle defined by an offset downstream direction of the k-th plane and a (k1)-th ridge line, and B.sup.k.sub.k is an angle defined by the offset downstream direction of the k-th plane and a k-th ridge line.

The present invention relates to a method for growing a gallium oxide single crystal and an apparatus for growing a single crystal, and according to one aspect of the present invention, the method includes providing a gallium oxide raw material in a crucible containing iridium, injecting carbon dioxide so that a preset carbon dioxide partial pressure is formed to suppress the loss of iridium, melting the gallium oxide raw material provided in the crucible, and producing a gallium oxide single crystal from the melt.

The present invention relates to a method for growing a gallium oxide single crystal and an apparatus for growing a single crystal, and according to one aspect of the present invention, the method includes providing a gallium oxide raw material in a crucible containing iridium, injecting carbon dioxide so that a preset carbon dioxide partial pressure is formed to suppress the loss of iridium, melting the gallium oxide raw material provided in the crucible, and producing a gallium oxide single crystal from the melt.

A preparation method and a use of 2D MoS.sub.2 materials are provided. Molybdenum source and sulfur powder are used as raw materials, and inert gas is used as carrier gas. Through an intermediate evaporation process, the raw materials are transported to the molten glass surface and deposited into solid molybdenum sulfide. In the subsequent etching-spreading-sulfurization-precipitation process, ultra-high quality and ultra-large area MoS.sub.2 single-crystal domains are obtained under normal pressure and without hydrogenation. The single-crystal domain size of the prepared 2D MoS.sub.2 material can reach 1.5 cm, and then grow into a wafer-level 2D MoS.sub.2 material with a size of 2 inches and a thickness of 1-2 layers.

A preparation method and a use of 2D MoS.sub.2 materials are provided. Molybdenum source and sulfur powder are used as raw materials, and inert gas is used as carrier gas. Through an intermediate evaporation process, the raw materials are transported to the molten glass surface and deposited into solid molybdenum sulfide. In the subsequent etching-spreading-sulfurization-precipitation process, ultra-high quality and ultra-large area MoS.sub.2 single-crystal domains are obtained under normal pressure and without hydrogenation. The single-crystal domain size of the prepared 2D MoS.sub.2 material can reach 1.5 cm, and then grow into a wafer-level 2D MoS.sub.2 material with a size of 2 inches and a thickness of 1-2 layers.