A method for making MnBi.sub.2Te.sub.4 single crystal is provided. The method includes: providing a mixture of polycrystalline MnTe and polycrystalline Bi.sub.2Te.sub.3 in Molar ratio of 1.1:11:1.1; heating the mixture in a vacuum reaction chamber to 700 C.900 C., cooling the mixture to 570 C.600 C. slowly with a speed less than or equal to 1 C./hour, and annealing the mixture at 570 C.600 C. for a time above 10 days to obtain an intermediate product; and air quenching the intermediate product from 570 C.600 C. to room temperature. The method for making MnBi.sub.2Te.sub.4 single crystal is simple and has low cost.

Fabricating a crystalline metal-phosphide layer may include providing a crystalline base substrate and a step of forming a crystalline metal-source layer. The method may further include performing a chemical conversion reaction to convert the metal-source layer to the crystalline metal phosphide layer. One or more corresponding semiconductor structures can be also provided.

The present invention belongs to the field of semiconductor materials preparation technology, and relates to a preparation method of gallium oxide/copper gallium oxide heterojunction. In this method, the gallium oxide is pre-treated before the copper source is deposited on the pre-treated gallium oxide, or directly cover the copper source layer on the pretreated gallium oxide. Then, the gallium oxide with copper source is placed in a high temperature furnace in proper form and then heat treated for a certain time under certain conditions, so that the copper atomics can be controlled to diffuse into gallium oxide to form corresponding copper-gallium-oxygen alloys. Further the copper-gallium-oxygen alloys forms gallium oxide/copper gallium oxide heterojunction having good interfacial properties with gallium oxide which does not undergo copper diffusion. The advantage is that the high quality copper gallium oxide material can be prepared. The required equipment and process are simple and controllable.

Provided is a method of manufacturing MoS.sub.2 having a 1T crystal structure. The method includes performing phase transition from a 2H crystal structure of MoS.sub.2 to the 1T crystal structure by reacting MoS.sub.2 having the 2H crystal structure with CO gas. The phase transition includes annealing the MoS.sub.2 having the 2H crystal structure in an atmosphere including CO gas.

Provided is a method of manufacturing MoS.sub.2 having a 1T crystal structure. The method includes performing phase transition from a 2H crystal structure of MoS.sub.2 to the 1T crystal structure by reacting MoS.sub.2 having the 2H crystal structure with CO gas. The phase transition includes annealing the MoS.sub.2 having the 2H crystal structure in an atmosphere including CO gas.

A compound strontium fluoroborate, nonlinear optical crystal of strontium fluoroborate, preparation method thereof; the chemical formula of the compound is SrB5O7F3, its molecular weight is 310.67, and it is prepared by solid-state reaction; the chemical formula of the crystal is SrB5O7F3, its molecular weight is 310.67, the crystal is of the orthorhombic series, the space group is Ccm21, and the crystal cell parameters are=10.016(6) , b=8.654(6)(4) , c=8.103(5) , Z=4, and V=702.4(8) 3. A SrB5O7F3 nonlinear optical crystal has uses in the preparation of a harmonic light output when doubling, tripling, quadrupling, quintupling, or sextupling the frequency of a 1064-nm fundamental-frequency light outputted by a Nd:YAG laser, or the generation of a deep-ultraviolet frequency doubling light output lower than 200 nm, or in the preparation of a frequency multiplier, upper or lower frequency converter, or an optical parametric oscillator.

A compound strontium fluoroborate, nonlinear optical crystal of strontium fluoroborate, preparation method thereof; the chemical formula of the compound is SrB5O7F3, its molecular weight is 310.67, and it is prepared by solid-state reaction; the chemical formula of the crystal is SrB5O7F3, its molecular weight is 310.67, the crystal is of the orthorhombic series, the space group is Ccm21, and the crystal cell parameters are=10.016(6) , b=8.654(6)(4) , c=8.103(5) , Z=4, and V=702.4(8) 3. A SrB5O7F3 nonlinear optical crystal has uses in the preparation of a harmonic light output when doubling, tripling, quadrupling, quintupling, or sextupling the frequency of a 1064-nm fundamental-frequency light outputted by a Nd:YAG laser, or the generation of a deep-ultraviolet frequency doubling light output lower than 200 nm, or in the preparation of a frequency multiplier, upper or lower frequency converter, or an optical parametric oscillator.

An oriented piezoelectric film, wherein a crystal forming the oriented piezoelectric film, is a perovskite type crystal of the general formula of Ba.sub.1-xCa.sub.xTi.sub.1-yZr.sub.yO.sub.3 (0x0.2, and 0y0.2), and the oriented piezoelectric film has (111) orientation according to a pseudocubic crystal notation.

There is provided a semiconductor nanocrystal or quantum dot comprising a core made of a material and at least one shell made of another material. Also there is provided a composite comprising a plurality of such nanocrystals or quantum dots. Moreover, there is provided a method of measuring the temperature of an object or area, comprising using a temperature sensor comprising a semiconductor nanocrystal or quantum dot of the invention.

There is provided a semiconductor nanocrystal or quantum dot comprising a core made of a material and at least one shell made of another material. Also there is provided a composite comprising a plurality of such nanocrystals or quantum dots. Moreover, there is provided a method of measuring the temperature of an object or area, comprising using a temperature sensor comprising a semiconductor nanocrystal or quantum dot of the invention.