A single crystal substrate is provided and is characterized in that the single crystal substrate has a foundation substrate provided with a plurality of grooves, which include a first crystal face and a second crystal face opposed to the first crystal face in an inner face thereof, and the extending direction of which is a <110> direction, and an angle formed by the first crystal face and the second crystal face is more than 70.6. Further, it is preferred that the angle formed by the first crystal face and the second crystal face is 100 or more and 176 or less.

A window assembly heat transfer system is disclosed in which a window member has a selected transparency to monitored or sensed light wavelengths. One or more passages are provided in the window member for flowing a single-phase or two-phase heat transfer fluid, the passages being optically non-transparent to the monitored or sensed light wavelengths. A mechanism allows either evaporation or condensation of the fluid and/or balancing of a flow of the fluid within the passages. In one embodiment, the window assembly can be made by producing passages in a top surface of a first single plate, optionally producing passages in a bottom surface of a second single plate and bonding the top surface of the first plate to a bottom surface of a second single plate to form the window member with the passage or passages. In another embodiment, the window assembly can be made by providing a core around which the window member material is grown and thereafter removing the core to produce the passage or passages.

A window assembly heat transfer system is disclosed in which a window member has a selected transparency to monitored or sensed light wavelengths. One or more passages are provided in the window member for flowing a single-phase or two-phase heat transfer fluid, the passages being optically non-transparent to the monitored or sensed light wavelengths. A mechanism allows either evaporation or condensation of the fluid and/or balancing of a flow of the fluid within the passages. In one embodiment, the window assembly can be made by producing passages in a top surface of a first single plate, optionally producing passages in a bottom surface of a second single plate and bonding the top surface of the first plate to a bottom surface of a second single plate to form the window member with the passage or passages. In another embodiment, the window assembly can be made by providing a core around which the window member material is grown and thereafter removing the core to produce the passage or passages.

A window assembly heat transfer system is disclosed in which a window member has a selected transparency to monitored or sensed electromagnetic wavelengths. One or more passages are provided in the window member for flowing a single-phase or two-phase heat transfer fluid. A mechanism allows either evaporation or condensation of the fluid and/or balancing of a flow of the fluid within the passages. In one embodiment, the window assembly can be made by producing passages in a top surface of a first single plate, optionally producing passages in a bottom surface of a second single plate and bonding the top surface of the first plate to a bottom surface of a second single plate to form the window member with the passage or passages. In another embodiment, the window assembly can be made by providing a core around which the window member material is grown and thereafter removing the core to produce the passage or passages.

A window assembly heat transfer system is disclosed in which a window member has a selected transparency to monitored or sensed electromagnetic wavelengths. One or more passages are provided in the window member for flowing a single-phase or two-phase heat transfer fluid. A mechanism allows either evaporation or condensation of the fluid and/or balancing of a flow of the fluid within the passages. In one embodiment, the window assembly can be made by producing passages in a top surface of a first single plate, optionally producing passages in a bottom surface of a second single plate and bonding the top surface of the first plate to a bottom surface of a second single plate to form the window member with the passage or passages. In another embodiment, the window assembly can be made by providing a core around which the window member material is grown and thereafter removing the core to produce the passage or passages.

In some embodiments, a selective cyclic (optionally dry) etching of a first surface of a substrate relative to a second surface of the substrate in a reaction chamber by chemical atomic layer etching comprises forming a modification layer using a first plasma and etching the modification layer. The first surface comprises carbon and/or nitride and the second surface does not comprise carbon and/or nitride.

A device includes a semiconductor substrate containing gallium nitride and having a crystal face inclined from 0.05 to 15 inclusive with respect to the c-plane. The semiconductor substrate includes an irregular portion on the crystal face, and the contact angle of pure water having a specific resistance of 18 M.Math.cm or more on the surface of the irregular portion is 10 or less.

A device includes a semiconductor substrate containing gallium nitride and having a crystal face inclined from 0.05 to 15 inclusive with respect to the c-plane. The semiconductor substrate includes an irregular portion on the crystal face, and the contact angle of pure water having a specific resistance of 18 M.Math.cm or more on the surface of the irregular portion is 10 or less.

A device for growing single crystals, in particular of silicon carbide, includes a crucible, which crucible defines an outer lateral surface and moreover delimits an accommodation space with an axial extension between a bottom section and an opening section, wherein the accommodation space is designed for growing the single crystals, wherein the device includes at least one seed crystal layer, wherein the seed crystal layer is assembled from multiple seed crystal plates in a tessellated manner.

A device for growing single crystals, in particular of silicon carbide, includes a crucible, which crucible defines an outer lateral surface and moreover delimits an accommodation space with an axial extension between a bottom section and an opening section, wherein the accommodation space is designed for growing the single crystals, wherein the device includes at least one seed crystal layer, wherein the seed crystal layer is assembled from multiple seed crystal plates in a tessellated manner.