Abstract: A nonlinear optical crystal structure is provided. The nonlinear optical crystal structure includes a plurality of two-dimensional material films, wherein the plurality of two-dimensional material films are stacked in a direction perpendicular to a two-dimensional plane thereof, and two-dimensional material films adjacent to each other are bonded by van der Waals forces, each of the plurality of two-dimensional material films is a crystal with a center-inversion-asymmetric crystal structure, and has a predetermined lattice orientation parallel to the two-dimensional plane in a direction parallel to the two-dimensional plane, there is a non-zero twist angle between the two-dimensional material films adjacent to each other, and the twist angle is an included angle between predetermined lattice orientations of the two-dimensional material films adjacent to each other in the same two-dimensional plane, and a thickness of each of the plurality of two-dimensional material films is greater than 5 nm.

Abstract: Provided is a preparation method for an ultrahigh-conductivity multilayer single-crystal laminated copper material, where multiple layers of single-crystal copper foils are laminated together to form a laminate, and the laminate is pressurized and annealed as one piece by performing pressurizing and high-temperature annealing at the same time, or the laminate is pressed as one piece by means of direct hot rolling, thereby obtaining an ultrahigh-conductivity multi-layer single-crystal laminated copper material, whereby, according to the method, multiple layers of single-crystal copper foils are used as raw materials, an ultrahigh-conductivity multi-layer single-crystal laminated copper material is prepared by means of hot rolling or pressing and annealing, and the conductivity of the copper material is greater than or equal to 105% IACS.

Abstract: A method for clonal-growth of a single-crystal metal, including: using copper as an example, placing an existing small-sized single-crystal copper foil with a plane of any index on a copper foil that needs to be single-crystallized, and performing annealing to obtain, by cloning, a large-area (in meters) single-crystal copper foil with the same surface index as that of the parent facet. The method solves the difficult problem of large-area single-crystal copper foil preparation. By performing annealing, a parent single-crystal copper foil with a very small size (˜0.25 cm2) can be cloned to produce a large-area (˜700 cm2) single-crystal copper foil, which is an increase in area of about 3000 times.

Abstract: A purification method for a copper foil, which belongs to the field of material purification. The purification method for a copper foil comprises: placing an assembly in a central temperature zone of a tubular furnace, and annealing same for at least 5 h in a mixed atmosphere of an inert gas and hydrogen under the condition that the temperature of the central temperature zone is maintained at 1050-1070° C., so as to obtain a purified single-crystal copper foil, wherein the assembly is composed of a polycrystalline copper foil containing impurities and a carrier supporting the polycrystalline copper foil, the polycrystalline copper foil is a rolled copper foil, the flow of the inert gas is 500-600 sccm, and the flow of the hydrogen is 30-100 sccm.

Abstract: A method for preparing a large-scale two-dimensional single crystal material stack which has an interlayer rotation angle. Single crystal substrates are stacked and rotated at a specific angle, a two-dimensional single crystal material is epitaxial on the surface thereof, and then an upper layer and a lower layer of the two-dimensional single crystal material are attached, and a layer of the single crystal substrates on the surface is removed so as to obtain a two-dimensional single crystal stack which has a specific rotation angle. A large-scale two-dimensional single crystal material stack which has an interlayer rotation angle prepared by the described method.

Abstract: Provided is a preparation method for an ultrahigh-conductivity multilayer single-crystal laminated copper material, where multiple layers of single-crystal copper foils are laminated together to form a laminate, and the laminate is pressurized and annealed as one piece by performing pressurizing and high-temperature annealing at the same time, or the laminate is pressed as one piece by means of direct hot rolling, thereby obtaining an ultrahigh-conductivity multi-layer single-crystal laminated copper material, whereby, according to the method, multiple layers of single-crystal copper foils are used as raw materials, an ultrahigh-conductivity multi-layer single-crystal laminated copper material is prepared by means of hot rolling or pressing and annealing, and the conductivity of the copper material is greater than or equal to 105% IACS.

Abstract: A method for clonal-growth of a single-crystal metal, including: using copper as an example, placing an existing small-sized single-crystal copper foil with a plane of any index on a copper foil that needs to be single-crystallized, and performing annealing to obtain, by cloning, a large-area (in meters) single-crystal copper foil with the same surface index as that of the parent facet. The method solves the difficult problem of large-area single-crystal copper foil preparation. By performing annealing, a parent single-crystal copper foil with a very small size (˜0.25 cm2) can be cloned to produce a large-area (˜700 cm2) single-crystal copper foil, which is an increase in area of about 3000 times.