A seed crystal for single crystal 4H-SiC growth of the present invention is a disk-shaped seed crystal for single crystal 4H-SiC growth having a diameter of more than 150 mm and having a thickness within a range of more than or equal to 1 mm and less than or equal to 0.03 times of the diameter, in which one surface on which the single crystal 4H-SiC is grown is a mirror surface and an Ra of the other surface is more than 10 nm, and an absolute value of magnitude of waviness in a state where the seed crystal is freely deformed so that an internal stress distribution is reduced is less than or equal to 12 μm.

An optical element for a deep-ultraviolet light source includes a crystalline substrate; a coating on an exterior surface of the crystalline substrate, the coating having a thickness along a direction that extends away from the exterior surface; and a structure on and/or in the coating, the structure including a plurality of features that extend away from the crystalline substrate along the direction. The features include an amorphous dielectric material and are arranged such that an index of refraction of the structure varies along the direction.

Disclosed are a modified nanocrystalline strip, a preparation method therefor, and an application thereof. The preparation method comprises: performing rolling treatment on a nanocrystalline strip with a double-sided adhesive adhered on one side to obtain a micro-crushed nanocrystalline strip; performing acid etching surface treatment on the obtained micro-crushed nanocrystalline strip; performing alkaline washing surface treatment on the nanocrystalline strip subjected to acid etching surface treatment; sequentially washing with water and washing with alcohol the nanocrystalline strip obtained by the alkaline washing surface treatment, and then drying same; and performing micro-oxidation treatment on the dried nanocrystalline strip to obtain a modified nanocrystalline strip.

The present invention provides a monocrystalline SiC substrate with an asymmetric shape for enhancing substrate stiffness against thermal induced deformations, the substrate comprising: a main region, and an asymmetric region located at a peripheral region of the substrate and adjacent to the main region, wherein the asymmetric region is inclined inwards, relative to the main region, to provide an asymmetric shape to the substrate. The present invention also provides a method of producing one or more substrates with an asymmetric shape, comprising: performing a multi-wire sawing process in which one or more substrates are cut with an wire-sawing web from an ingot placed on a stage, and cutting the one or more substrates with the asymmetric shape by controlling a relative movement between the wire-sawing web and the stage, the relative movement causing the wire-sawing web to describe a non-linear sawing path across the ingot to cut the asymmetric shape.

The present invention provides a monocrystalline SiC substrate with an asymmetric shape for enhancing substrate stiffness against thermal induced deformations, the substrate comprising: a main region, and an asymmetric region located at a peripheral region of the substrate and adjacent to the main region, wherein the asymmetric region is inclined inwards, relative to the main region, to provide an asymmetric shape to the substrate. The present invention also provides a method of producing one or more substrates with an asymmetric shape, comprising: performing a multi-wire sawing process in which one or more substrates are cut with an wire-sawing web from an ingot placed on a stage, and cutting the one or more substrates with the asymmetric shape by controlling a relative movement between the wire-sawing web and the stage, the relative movement causing the wire-sawing web to describe a non-linear sawing path across the ingot to cut the asymmetric shape.

Provided are a method of cleaning a group III nitride single crystal substrate which enables the roughness of a nitrogen-polar face of the group III nitride single crystal substrate to be suppressed to remove foreign substances, and a method of producing a group III nitride single crystal substrate. The method of cleaning a group III nitride single crystal substrate having a group III element-polar face, and the nitrogen-polar face opposite the group III element-polar face includes: cleaning the nitrogen-polar face with a detergent including a fluoroorganic compound.

Provided are a method of cleaning a group III nitride single crystal substrate which enables the roughness of a nitrogen-polar face of the group III nitride single crystal substrate to be suppressed to remove foreign substances, and a method of producing a group III nitride single crystal substrate. The method of cleaning a group III nitride single crystal substrate having a group III element-polar face, and the nitrogen-polar face opposite the group III element-polar face includes: cleaning the nitrogen-polar face with a detergent including a fluoroorganic compound.

A method of a growing an embedded single crystal diamond structure, comprising: disposing a single crystal diamond on a non-diamond substrate, wherein the non-diamond substrate is larger than the single crystal diamond; masking a top portion of the single crystal diamond using a masking material; and using a chemical vapor deposition (CVD) growth chamber, growing polycrystalline diamond material surrounding the single crystal diamond in order to join the single crystal diamond to the polycrystalline diamond material.

Provided are a high quality silicon carbide seed crystal, a silicon carbide crystal, a silicon carbide substrate, and a preparation method therefor. A high quality silicon carbide seed crystal is prepared, the dopant concentrations of a thermal insulation material, a graphite crucible, and a silicon carbide powder material are controlled, a specific crystal growth process and a wafer machining means are integrated, and a high quality silicon carbide substrate is obtained. The obtained silicon carbide substrate has a high crystalline quality and an extremely low amount of micropipes, screw dislocation density, and compound dislocation density; said substrate also has an extremely low p-type dopant concentration, exhibits superior electrical performance, and has a high surface quality.

Group-III element nitride semiconductor substrate including a first surface and a second surface that are easy to visually distinguish from each other. An end portion is easily detected with an optical sensor, a large effective area (area that can be used in device production) can be secured, and warping of the entirety of the substrate is reduced. A Group-III element nitride semiconductor substrate includes a first surface; and a second surface, wherein the first surface is a mirror surface, the second surface has a second-surface central region and a second-surface outer peripheral region, the second-surface central region is a mirror surface, and the second-surface outer peripheral region is a non-mirror surface.