# US 11,114,579 B2 · Method for preparing ultrathin two-dimensional nanosheets and applications thereof

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- Number: US 11,114,579 B2
- Document ID: US11114579B2
- Status: Granted
- Kind: B2
- Application number: 16/905,995
- Filed: 2020-06-19
- Published: 2020-12-24
- Granted: 2021-09-07
- Earliest claimed: 2019-06-19
- Assignees: University of Electronic Science and Technology of China
- Applicants: University of Electronic Science and Technology of China
- Inventors: Jie Xiong; Chuanhui Gong; Yang Wang; Gaofeng Rao; Chujun Yin; Chaoyi Yan; Junwei Chu; Jianwen Huang; Miao Zhang; Xinrui Chen; Yuqing Liu; Chunyang Wu; Xianfu Wang; Liping Dai; Wanli Zhang; Yanrong Li
- Web page: https://patentgrep.com/patent/US11114579B2

## CPC

- H10F 71/128: {Annealing}
- H10F 77/16: Material structures, e.g. crystalline structures, film structures or crystal plane orientations
- C23C 8/10: Oxidising
- C23C 8/12: using elemental oxygen or ozone
- C23C 8/80: After-treatment
- C23C 14/042: {using masks}
- C23C 14/0694: {Halides}
- C23C 14/16: on metallic substrates or on substrates of boron or silicon
- C23C 14/18: on other inorganic substrates
- C23C 14/24: Vacuum evaporation
- C30B 25/10: Heating of the reaction chamber or the substrate
- C30B 25/183: {being provided with a buffer layer, e.g. a lattice matching layer}
- C30B 29/12: Halides
- C30B 29/64: Flat crystals, e.g. plates, strips or discs
- H10F 30/10: the devices being sensitive to infrared radiation, visible or ultraviolet radiation, and having no potential barriers, e.g. photoresistors
- H10F 77/12: Active materials
- H10F 77/20: Electrodes
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR

## Abstract

A method for preparing an ultrathin two-dimensional (2D) monocrystalline nanosheet, the method including: 1) placing BiX3 powder where X=I, Br, or Cl in a crucible, and putting the crucible on a first heating zone of a furnace disposed at a gas inlet of a quartz tube; placing substrates covered with metal sheets on a second heating zone of the furnace disposed at a gas outlet of the quartz tube; 2) vacuumizing the quartz tube; pumping Ar gas into the quartz tube until the air pressure is 101.325 kPa; pumping a carrier gas into the quartz tube; and 3) heating and maintaining the second heating zone; heating the first heating zone for BiX3 evaporation until producing chemical reaction between BiX3 and the metal sheets, and preparing ultrathin 2D nanosheets on the substrates simultaneously; and cooling the substrate naturally to 15-30° C.

## Claims

### Claim 1

A method, comprising:
placing BiX3 powder where X=I, Br, or Cl in a crucible, and putting the crucible on a first heating zone of a furnace disposed at a gas inlet of a quartz tube; placing substrates covered with metal sheets on a second heating zone of the furnace disposed at a gas outlet of the quartz tube;
vacuumizing the quartz tube by a mechanical pump; pumping Ar gas into the quartz tube until a gas pressure is equal to 101.325 kPa; pumping a carrier gas into the quartz tube and adjusting and maintaining a steady flow rate of the carrier gas; and
heating and maintaining the second heating zone; heating the first heating zone to evaporate BiX3 until the ultrathin 2D nanosheets are formed on the substrate; and cooling the substrate naturally to 15-30° C.

### Claim 2 (depends on 1)

The method of claim 1, wherein the metal sheets are unoxidized transition or naturally oxidized transition; the metal sheets and the substrates construct micro-nano scale confined space, and a gap distance between the metal sheets and the substrates is 0-100 microns.

### Claim 3 (depends on 2)

The method of claim 2, wherein the transition metal sheets are copper sheets or iron sheets.

### Claim 4 (depends on 1)

The method of claim 1, wherein the naturally oxidized transition metal sheets are oxidized in the air at 15-30° C. for 1-2 days.

### Claim 5

The method, comprising:
1) placing BiBr3 powder in a crucible, and putting the crucible on a first heating zone of a furnace disposed at a gas inlet of a quartz tube; placing substrates covered with copper sheets on a second heating zone of the furnace disposed at a gas outlet of the quartz tube; wherein a confined spacing gap between the copper sheets and the substrates is 0-100 μm;
2) vacuumizing the quartz tube to less than 0.1 Pa; pumping Ar gas into the quartz tube until an air pressure is equal to one atmosphere pressure; pumping mixed gas of Ar and H2 to the quartz tube and adjusting and maintaining a steady flow rate of the mixed gas; and
3) heating the second heating zone to a temperature of 275-325° C. and keeping the temperature for 10-60 min; heating the first heating zone to 200-275° C. for 3-20 min until producing chemical reaction between BiBr3 and metal sheets, and preparing ultrathin 2D nanosheets on the substrates simultaneously; and cooling the substrate naturally to 15-30° C., thereby yielding a two-dimensional ultrathin monocrystalline CuBr nanosheet.

### Claim 6 (depends on 5)

The method of claim 5, wherein the substrates in 1) are mica or graphene substrate and a mass of the BiBr3 powder is 2-200 mg.

### Claim 7 (depends on 5)

The method of claim 5, wherein the H2 in 2) is 0-10% (v/v) in the mixed gas and a flow velocity of the mixed gas is about 50-100 sccm.

### Claim 8 (depends on 5)

A two-dimensional ultrathin monocrystalline CuBr nanosheet prepared according to the method of claim 5, wherein a thickness of the two-dimensional ultrathin monocrystalline CuBr nanosheet is 0.9-200 nm and a sheet size thereof is 2-150 μm.

### Claim 9 (depends on 8)

A method for preparing a photodetector based on the two-dimensional ultrathin monocrystalline CuBr nanosheet of claim 8, the method comprising: depositing a silver electrode with a thickness of 25-100 nm using a copper mesh as a mask on the two-dimensional ultrathin monocrystalline CuBr nanosheet.

### Claim 10

A method, comprising:
1) placing BiI3 powder in a crucible, and putting the crucible on a first heating zone of a furnace disposed at a gas inlet of a quartz tube; placing substrates covered with naturally oxidized iron sheets on a second heating zone of the furnace disposed at a gas outlet of the quartz tube;
2) vacuumizing the quartz tube to less than 1 Pa; pumping Ar gas into the quartz tube until an air pressure is equal to one atmosphere pressure; continuously pumping the Ar gas to the quartz tube with a flow velocity of 10-75 sccm; and
3) heating the second heating zone to a temperature of 370-450° C. and keeping the temperature for 10-60 min; heating the first heating zone to 450-520° C. for 5-20 min until producing chemical reaction between BiI3 and metal sheets, and preparing ultrathin 2D nanosheets on the substrates simultaneously; and cooling the substrate naturally to 15-30° C., thereby yielding a two-dimensional ultrathin monocrystalline Fe3O4 nanosheet.

### Claim 11 (depends on 10)

The method of claim 10, wherein a mass of the BiI3 powder in 1) is 1-20 mg and the substrates are mica.

### Claim 12 (depends on 10)

The method of claim 10, wherein the naturally oxidized iron sheets in 1) is obtained by placing iron sheets in the air with 15-30° C. for 1 to 2 days.

### Claim 13 (depends on 10)

A two-dimensional ultrathin monocrystalline Fe3O4 nanosheet prepared according to the method of claim 10, wherein a thickness of the two-dimensional ultrathin monocrystalline Fe3O4 nanosheet is 1.95-100 nm and a sheet size thereof is 1-20 nm.

### Claim 14 (depends on 13)

A method for preparing the two-dimensional ultrathin monocrystalline Fe3O4 nanosheet of claim 13, the method comprising: transferring the Fe3O4 nanosheet from a mica substrate to an Si/SiO2 substrate; depositing an electrode by electron beam exposure and thermal evaporation, the electrode comprising a Cr with a thickness of 1-10 nm and an Au with a thickness of 10-100 nm.

### Claim 15

A method, comprising:
1) placing BiBr3 powder in a crucible, and putting the crucible on a first heating zone of a furnace disposed at a gas inlet of a quartz tube; placing substrates covered with naturally oxidized copper sheets on a second heating zone of the furnace disposed at a gas outlet of the quartz tube;
2) vacuumizing the quartz tube to less than 0.1 Pa; pumping Ar gas into the quartz tube until an air pressure is equal to one atmosphere pressure; continuously pumping the Ar gas to the quartz tube with a flow velocity of 25-50 sccm; and
3) heating the second heating zone to a temperature of 380-400° C. and keeping the temperature for 1-60 min; heating the first heating zone to 220-275° C. for 5-30 min until producing chemical reaction between BiI3 and metal sheets, and preparing ultrathin 2D nanosheets on the substrates simultaneously; and cooling the substrate naturally to 15-30° C., thereby yielding a two-dimensional ultrathin monocrystalline BiOBr nanosheet.

### Claim 16 (depends on 15)

The method of claim 15, wherein a mass of the BiBr3 powder in 1) is 2-50 mg.

### Claim 17 (depends on 15)

The method of claim 15, wherein the naturally oxidized copper sheets in 1) is obtained by placing the copper sheets in the air with 15-30° C. for 1 to 2 days.

### Claim 18 (depends on 15)

The method of claim 15, wherein the cooling in 3) is natural cooling or rapid cooling, and a rate of the rapid cooling is over 50° C./min.

### Claim 19 (depends on 15)

A two-dimensional ultrathin monocrystalline BiOBr nanosheet prepared according to the method of claim 15, wherein a growth crystal surface of the two-dimensional ultrathin monocrystalline BiOBr nanosheet is (001), a thickness is 0.57-200 nm, and a sheet size is 0.5-70 nm.

### Claim 20 (depends on 19)

A method for preparing a photodetector based on the two-dimensional ultrathin monocrystalline BiOBr nanosheet of claim 19, the method comprising: transferring the BiOBr nanosheet with a thickness of 0.57 nm-20 nm onto a silicon substrate using a wet method, and manufacturing an electrode by electron beam lithography and thermal evaporation.