The present invention provides monocrystalline 4H—SiC semi-finished products having a specific orientation of its crystal structure which is set such as to reduce or even eliminate the occurrence of cracks or fissures during mechanical processing, and method of producing same. The monocrystalline 4H—SiC semi-finished product, which has a longitudinal axis and an at least partially curved lateral surface parallel to said longitudinal axis, is characterized in that the crystal structure of the 4H—SiC semi-finished product is oriented with respect to the longitudinal axis such that at each position on the lateral surface of the semi-finished product there is a line segment which is intersected by at least a predetermined minimum number of parallel cleavage planes of the {1010} form per unit length, wherein the line segment is defined by a plane tangent to the lateral surface at said position.

The present invention provides monocrystalline 4H—SiC semi-finished products having a specific orientation of its crystal structure which is set such as to reduce or even eliminate the occurrence of cracks or fissures during mechanical processing, and method of producing same. The monocrystalline 4H—SiC semi-finished product, which has a longitudinal axis and an at least partially curved lateral surface parallel to said longitudinal axis, is characterized in that the crystal structure of the 4H—SiC semi-finished product is oriented with respect to the longitudinal axis such that at each position on the lateral surface of the semi-finished product there is a line segment which is intersected by at least a predetermined minimum number of parallel cleavage planes of the {1010} form per unit length, wherein the line segment is defined by a plane tangent to the lateral surface at said position.

The present invention provides monocrystalline 4H—SiC substrates having a specific orientation of its crystal structure which is set such as to reduce or even eliminate the occurrence of cracks or fissures during mechanical processing, and method of producing same. The monocrystalline 4H—SiC substrate, which has a longitudinal axis and an at least partially curved lateral surface parallel to said longitudinal axis, is characterized in that the crystal structure of the 4H—SiC substrate is oriented with respect to the longitudinal axis such that at each position on the lateral surface of the semi-finished product there is a line segment which is intersected by at least a predetermined minimum number of parallel cleavage planes of the {1010} form per unit length, wherein the line segment is defined by a plane tangent to the lateral surface at said position.

A large grain quasi-single-crystal film and a manufacturing method thereof are provided. The metal film having the <111> preferred orientation on its surface is subjected to mechanical tensile force to make the arrangement of crystal grains more ordered. The metal film is grown into a film with large crystal grains having an average diameter of over 500 microns by annealing at a temperature below the recrystallization temperature, thereby obtaining a large grain quasi-single-crystal film having the preferred directions of three axes. The large grain quasi-single-crystal film has a <110> preferred orientation along the tensile direction and a <211> preferred orientation along the direction vertical to the tensile force, and maintains a <111> preferred orientation on its top surface. The present invention can be used to produce highly anisotropic large-area quasi-single-crystal films, and can also be applied to grow 2-dimensional materials or develop anisotropic structures.

Reducing the microvoid (MV) density in AlN ameliorates numerous problems related to cracking during crystal growth, etch pit generation during the polishing, reduction of the optical transparency in an AlN wafer, and, possibly, growth pit formation during epitaxial growth of AlN and/or AlGaN. This facilitates practical crystal production strategies and the formation of large, bulk AlN crystals with low defect densities—e.g., a dislocation density below 10.sup.4 cm.sup.−2 and an inclusion density below 10.sup.4 cm.sup.−3 and/or a MV density below 10.sup.4 cm.sup.−3.

A laser system includes a nonlinear optical (NLO) crystal, wherein the NLO crystal is annealed within a selected temperature range. The NLO crystal is passivated with at least one of hydrogen, deuterium, a hydrogen-containing compound or a deuterium-containing compound to a selected passivation level. The system further includes at least one light source, wherein at least one light source is configured to generate light of a selected wavelength and at least one light source is configured to transmit light through the NLO crystal. The system further includes a crystal housing unit configured to house the NLO crystal.

A laser system includes a nonlinear optical (NLO) crystal, wherein the NLO crystal is annealed within a selected temperature range. The NLO crystal is passivated with at least one of hydrogen, deuterium, a hydrogen-containing compound or a deuterium-containing compound to a selected passivation level. The system further includes at least one light source, wherein at least one light source is configured to generate light of a selected wavelength and at least one light source is configured to transmit light through the NLO crystal. The system further includes a crystal housing unit configured to house the NLO crystal.

A method for structuring a decorative or technical pattern in the thickness of an object made of an at least partially transparent amorphous, semi-crystalline or crystalline material, wherein the object is made of an at least partially transparent material including a top surface and a bottom surface which extends away from the top surface. The top or bottom surfaces is provided with a mask defining an opening whose outline corresponds to the profile of the pattern to be structured, the mask covering the top or bottom surface at the positions which are not to be structured. The pattern is structured with a mono- or multicharged ion beam through the opening of the mask, wherein the mechanical properties of the mask are sufficient to prevent the ions of the ion beam from etching the top or bottom surface at the positions where this top or bottom surface is covered by the mask.

A method for manufacturing polycrystalline silicon fragments includes producing a polycrystalline silicon rod by the Siemens method; crushing the polycrystalline silicon rod to obtain polycrystalline silicon fragments; and cleaning by etching the polycrystalline silicon fragments in a cleaning tank. In the cleaning, small pieces of the polycrystalline silicon having controlled shapes and sizes are present in the cleaning tank and the weight change of the small pieces of the polycrystalline silicon before and after the etching is measured to thereby manage the cleaning.

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.