A nonlinear optical crystal of guanidinium tetrafluoroborate has a chemical formula of [C(NH.sub.2).sub.3]BF.sub.4 and a molecular weight of 146.89, belongs to the trigonal crystal system, has a space group of R3m; has lattice parameters of a=7.4634(10)Å, b=7.4634(10)Å, c=9.1216(19) (6)Å, and Z=3; has an ultraviolet cutoff edge of 200 nm; and has a frequency-multiplication response that is 4-5 times that of the commercialized nonlinear optical crystal KDP. A hydrothermal method, a room-temperature solution method, an evaporation method or a solvothermal method is used to grow the crystal in a centimeter-scaled size. The crystal can produce frequency-doubling, frequency-tripling, frequency-quadrupling, frequency-quintupling or frequency-sextupling harmonic light output from the fundamental frequency light of 1064 nm generated by a Nd:YAG laser, and/or can produce ultraviolet and deep-ultraviolet frequency-multiplication light output below 200 nm.

Embodiments disclosed herein include potassium sodium niobate (KNN) films and methods of making such films. In an embodiment, a method of forming a potassium sodium niobate (KNN) film comprises preparing a solution comprising water, potassium hexaniobate salts, and sodium hexaniobate salts. In an embodiment, the solution is spin coated onto a substrate to form a film on at least a portion of a surface of the substrate. In an embodiment, the method may further comprise heat treating the film.

Embodiments disclosed herein include potassium sodium niobate (KNN) films and methods of making such films. In an embodiment, a method of forming a potassium sodium niobate (KNN) film comprises preparing a solution comprising water, potassium hexaniobate salts, and sodium hexaniobate salts. In an embodiment, the solution is spin coated onto a substrate to form a film on at least a portion of a surface of the substrate. In an embodiment, the method may further comprise heat treating the film.

A film formation apparatus is configured to epitaxially grow a film on a surface of a substrate, and the film formation apparatus may include: a stage configured to allow the substrate to be mounted thereon; a heater configured to heat the substrate; a mist supply source configured to supply mist of a solution that comprises a solvent and a material of the film dissolved in the solvent; a heated-gas supply source configured to supply heated gas that comprises gas constituted of a same material as a material of the solvent and has a higher temperature than the mist; and a delivery device configured to deliver the mist and the heated gas to the surface of the substrate.

A film formation apparatus is configured to epitaxially grow a film on a surface of a substrate, and the film formation apparatus may include: a stage configured to allow the substrate to be mounted thereon; a heater configured to heat the substrate; a mist supply source configured to supply mist of a solution that comprises a solvent and a material of the film dissolved in the solvent; a heated-gas supply source configured to supply heated gas that comprises gas constituted of a same material as a material of the solvent and has a higher temperature than the mist; and a delivery device configured to deliver the mist and the heated gas to the surface of the substrate.

A method for making a nanoimprinted perovskite film or a perovskite crystal. The method includes applying a solution onto a substrate, thereby forming a precursor film or a precursor crystal, wherein the solution comprises an organo-metal halide precursor in a solvent. The method also includes fabricating an organo-metal halide perovskite film or an organo-metal halide perovskite crystal, wherein fabricating includes annealing the precursor film or the precursor crystal, thereby at least partially evaporating the solvent. The method also includes imprinting the organo-metal halide perovskite film or the organo-metal halide perovskite crystal with a mold, thereby forming an imprinted film or an imprinted crystal. The method also includes separating the mold from the imprinted film or the imprinted crystal, thereby forming the perovskite film or the perovskite crystal.

Embodiments disclosed herein include potassium sodium niobate (KNN) films and methods of making such films. In an embodiment, a method of forming a potassium sodium niobate (KNN) film comprises preparing a solution comprising water, potassium hexaniobate salts, and sodium hexaniobate salts. In an embodiment, the solution is spin coated onto a substrate to form a film on at least a portion of a surface of the substrate. In an embodiment, the method may further comprise heat treating the film.

Embodiments disclosed herein include potassium sodium niobate (KNN) films and methods of making such films. In an embodiment, a method of forming a potassium sodium niobate (KNN) film comprises preparing a solution comprising water, potassium hexaniobate salts, and sodium hexaniobate salts. In an embodiment, the solution is spin coated onto a substrate to form a film on at least a portion of a surface of the substrate. In an embodiment, the method may further comprise heat treating the film.

Hydrothermal methods for the synthesis of bulk crystals of alkaline earth metal stannates are described. Methods can be utilized for growth of large, single crystals of alkaline earth metal stannates including fully cubic BaSnO.sub.3 and SrSnO.sub.3.

Hydrothermal methods for the synthesis of bulk crystals of alkaline earth metal stannates are described. Methods can be utilized for growth of large, single crystals of alkaline earth metal stannates including fully cubic BaSnO.sub.3 and SrSnO.sub.3.