阅读说明：本技术 一种新型超薄三硒化二铬纳米片磁性材料及其制备和应用 (Novel ultrathin chromium triselenide nanosheet magnetic material and preparation and application thereof ) 是由 王笑 张丹亮 易琛 朱小莉 潘安练 于 2020-10-27 设计创作，主要内容包括：本发明涉及一种新型超薄三硒化二铬纳米片磁性材料及其制备和应用,属于二维磁性材料开发技术领域。所述新型超薄三硒化二铬纳米片磁性材料,为片状结构；其中,单个片状三硒化二铬纳米片中,厚度为单个晶胞厚度～N个晶胞厚度；所述N大于1；所述单个片状三硒化二铬纳米片的尺寸大于等于18微米。其制备方法为：在保护气氛下,将硒气和含铬气体置于800-900℃的环境中进行化学气相沉积,得到三硒化二铬纳米片。本发明所设计和制备的三硒化二铬纳米片可应用于过渡金属硫化物的能谷调控；其能谷调控效果明显并能在大气环境下稳定工作。(The invention relates to a novel ultrathin chromium diselenide nanosheet magnetic material, and preparation and application thereof, and belongs to the technical field of development of two-dimensional magnetic materials. The novel ultrathin chromium diselenide nanosheet magnetic material is of a sheet structure; wherein, in the single flaky chromium diselenide nanosheet, the thickness is from single unit cell thickness to N unit cell thicknesses; the N is greater than 1; the size of the single flaky dichromium triselenide nano sheet is more than or equal to 18 microns. The preparation method comprises the following steps: and under the protective atmosphere, placing the selenium gas and the chromium-containing gas in an environment of 800-900 ℃ for chemical vapor deposition to obtain the chromium diselenide nanosheet. The chromium diselenide nanosheet designed and prepared by the invention can be applied to energy valley regulation of transition metal sulfides; the energy-valley regulating effect is obvious and the device can stably work in atmospheric environment.)

1. A novel ultrathin chromium triselenide nanosheet magnetic material; the method is characterized in that: the novel ultrathin chromium diselenide nanosheet magnetic material is of a sheet structure; wherein, in the single flaky chromium diselenide nanosheet, the thickness is from single unit cell thickness to N unit cell thicknesses; the N is greater than 1; the size of the single flaky dichromium triselenide nano sheet is more than or equal to 18 microns.

2. A novel ultra-thin dichromium triselenide nanosheet magnetic material according to claim 1; the method is characterized in that:

the vertical projection of the single flaky chromium triselenide nanosheet is triangular or hexagonal;

and N is greater than 1 and less than or equal to 5.

3. A novel ultra-thin dichromium triselenide nanosheet magnetic material according to claim 1; the method is characterized in that: the size of a single flaky dichromium triselenide nanosheet can reach 120 microns or more.

4. A method for preparing a novel ultra-thin dichromium triselenide nanosheet magnetic material as defined in any one of claims 1-3, comprising the steps of: and under the protective atmosphere, placing the selenium gas and the chromium-containing gas in an environment of 800-900 ℃ for chemical vapor deposition to obtain the chromium diselenide nanosheet.

5. The preparation method of the novel ultrathin chromium diselenide nanosheet magnetic material as claimed in claim 4, wherein the preparation method comprises the following steps: the substrate used for deposition comprises 300nm-SiO₂One of a/Si substrate, a silicon-based substrate and mica.

6. The preparation method of the novel ultrathin chromium diselenide nanosheet magnetic material as claimed in claim 4, wherein the preparation method comprises the following steps: selenium powder is selected and placed in the upstream area of the tube furnace, catalyst particles and chromium powder are selected and uniformly mixed according to the mass ratio of 1:5-15, and the mixed catalyst and chromium powder are placed in the central area of the tube furnace; the catalyst is at least one selected from sodium chloride, sodium bromide, potassium chloride and potassium bromide, and is preferably sodium chloride.

7. The preparation method of the novel ultrathin chromium diselenide nanosheet magnetic material as claimed in claim 6, wherein the preparation method comprises the following steps: introducing high-purity argon of 100 sccm and 1000sccm, preferably 500sccm into a quartz tube of the front-end tube furnace, and keeping the argon for 10-20 minutes, preferably 15 minutes to discharge other gases in the tube so as to ensure a stable growth environment; then the argon flow is stabilized at 40-80sccm, preferably 60sccm, and the heating temperature of the tube furnace is raised to 850-900 ℃ for 25-30 minutes and the temperature is maintained for 5-10 minutes. And finally, naturally cooling the mixture to room temperature by using a constant-tube furnace to obtain the chromium diselenide nanosheet.

8. The preparation method of the novel ultrathin chromium diselenide nanosheet magnetic material as claimed in claim 6, wherein the preparation method comprises the following steps: the heating temperature of the selenium powder is 250-350 ℃, and the heating temperature of the mixed powder consisting of the sodium chloride particles and the chromium powder is 850-900 ℃.

9. Use of a novel ultra-thin dichromium triselenide nanosheet magnetic material of any one of claims 1-3; the method is characterized in that: transferring the single-layer transition metal chalcogenide to the designed dichromium triselenide nano-chip to form a single-layer transition metal chalcogenide/dichromium triselenide Van der Waals heterojunction, and using the single-layer transition metal chalcogenide/dichromium triselenide Van der Waals heterojunction for energy valley regulation; the transition metal chalcogenide includes a gravide dock.

10. The application of the novel ultrathin chromium diselenide nanosheet magnetic material as claimed in claim 9; the method is characterized in that: and transferring the single-layer docking disulfide to the dichromium triselenide nano-chip by a dry transfer method to form a single-layer docking disulfide/dichromium triselenide Van der Waals heterojunction.

Technical Field

The invention relates to a novel ultrathin chromium diselenide nanosheet magnetic material, and preparation and application thereof, and belongs to the technical field of development of two-dimensional magnetic materials.

Background

The two-dimensional magnetic material provides an ideal platform for the application of the spintronic device due to the unique nanoscale spin state of the two-dimensional magnetic material. At present, the two-dimensional magnetic material is mostly obtained by stripping from a bulk magnetic material, however, the stripped magnetic material is influenced by instability of the ambient atmosphere, and special protection is needed for working. On the other hand, the exfoliated two-dimensional van der waals layered magnetic material has problems of small size, random thickness, and the like. Therefore, two-dimensional magnetic materials need to solve the problem of controllable synthesis of good quality and stability. In contrast, two-dimensional non-layered magnetic materials have been rarely studied, especially with respect to their preparation. Cr (chromium) component_nX (X ═ S, Se, Te; 0 < n < 1), a class of non-layered transition metal sulfides, is of widespread interest because of its abundant compound structure and unique magnetic properties.

The magnetic proximity effect is an important approach to manipulating spintronics in heterojunctions. These effects are highly sensitive to interface electronic properties such as electron wavefunction overlap and band alignment. The recent emergence of two-dimensional magnetic materials opens new possibilities for exploring the proximity effect in van der waals heterojunctions. The control of the energy valley of transition metal chalcogenide based on the proximity effect of two-dimensional magnetic material/transition metal chalcogenide van der waals heterojunction has been studied, however, the two-dimensional magnetic material in the two-dimensional magnetic material/transition metal chalcogenide heterojunction is mechanically exfoliated.

Disclosure of Invention

The invention aims to provide a novel ultrathin magnetic material which has the advantages of ultrathin thickness, high stability, high Curie temperature, large magnetic moment and wide application field; a method for modulating the energy valley polarization by constructing a chemical vapor deposition grown two-dimensional magnetic material with a mechanically exfoliated monolayer of a transition metal chalcogenide van der Waals heterojunction is disclosed.

The invention relates to a novel ultrathin chromium triselenide nanosheet magnetic material; the novel ultrathin chromium diselenide nanosheet magnetic material is of a sheet structure; wherein, in the single flaky chromium diselenide nanosheet, the thickness is from single unit cell thickness to N unit cell thicknesses; the N is greater than 1; the size of the single flaky dichromium triselenide nano sheet is more than or equal to 18 microns.

The invention relates to a novel ultrathin chromium triselenide nanosheet magnetic material; the vertical projection of the single flaky dichromium triselenide nanosheet is triangular or hexagonal.

As a preferred scheme, the invention relates to a novel ultrathin chromium diselenide nanosheet magnetic material; and N is greater than 1 and less than or equal to 5.

The invention relates to a novel ultrathin chromium triselenide nanosheet magnetic material; the individual unit cell thickness is about 1.8 nm.

Under the technical condition of the invention, the size of a single flaky dichromium triselenide nanosheet can reach 120 microns or even more.

The invention relates to a preparation method of a novel ultrathin chromium triselenide nanosheet magnetic material, which comprises the following steps: and under the protective atmosphere, placing the selenium gas and the chromium-containing gas in an environment of 800-900 ℃ for chemical vapor deposition to obtain the chromium diselenide nanosheet.

The invention relates to a preparation method of a novel ultrathin chromium diselenide nanosheet magnetic material, wherein a substrate used for deposition comprises 300nm-SiO₂a/Si substrate, a silicon-based substrate, mica.

As a common scheme, the preparation method of the novel ultrathin chromium diselenide nanosheet magnetic material comprises the steps of selecting selenium powder to be placed in an upstream area of a tubular furnace, selecting catalyst particles and chromium powder to be uniformly mixed according to a mass ratio of 1:5-15, and placing the mixed catalyst and chromium powder in a central area of the tubular furnace; the catalyst is at least one selected from sodium chloride, sodium bromide, potassium chloride and potassium bromide, and is preferably sodium chloride. The dichromium selenide nanosheet magnetic material can be controllably synthesized by a chemical vapor deposition process.

In order to obtain a good-quality product, high-purity argon gas of 100 sccm and 1000sccm, preferably 500sccm, is introduced into the quartz tube of the tubular furnace before heating, and other gases in the tube are discharged while maintaining for 10-20 minutes, preferably 15 minutes, so as to ensure a stable growth environment of the atmosphere. Then the argon flow is stabilized at 40-80sccm, preferably 60sccm, and the heating temperature of the tube furnace is raised to 850-900 ℃ for 25-30 minutes and the temperature is maintained for 5-10 minutes. And finally, naturally cooling the mixture to room temperature by using a constant-tube furnace to obtain the chromium diselenide nanosheet.

In the invention, the volatilization temperature of the chromium powder is 1800 ℃, and the purpose of adding sodium chloride is to reduce the melting point of the chromium powder and the activation energy of the reaction, and simultaneously ensure that the chromium powder can smoothly obtain a set amount of steam at 850-900 ℃. The invention controls the ratio of sodium chloride particles to chromium powder to be 1:5-15, preferably 1: 10, and mainly aims to realize full reaction under low temperature and assist in controlling deposition speed, thereby providing necessary conditions for obtaining high-quality products.

The invention relates to a preparation method of a novel ultrathin chromium diselenide nanosheet magnetic material, wherein the purity of selenium powder is more than or equal to 99%, and the purity of chromium powder is more than or equal to 99%. In industrial application, commercial products such as selenium powder and chromium powder from alpha company can be purchased directly.

The invention relates to a preparation method of a novel ultrathin chromium diselenide nanosheet magnetic material, wherein the heating temperature of selenium powder is 250-350 ℃, and the heating temperature of mixed powder consisting of sodium chloride particles and chromium powder is 850-900 ℃.

The invention relates to the application of a novel ultrathin chromium triselenide nanosheet magnetic material; and transferring the single-layer docking disulfide to the designed chromium diselenide nanosheet to form a single-layer docking disulfide/chromium diselenide van der waals heterojunction, and using the single-layer docking disulfide/chromium diselenide van der waals heterojunction for energy valley regulation.

The invention relates to the application of a novel ultrathin chromium triselenide nanosheet magnetic material; and transferring the single-layer docking disulfide to the dichromium triselenide nano-chip by a dry transfer method to form a single-layer docking disulfide/dichromium triselenide Van der Waals heterojunction. The single-layer disulfide dock includes a single-layer disulfide dock prepared using a mechanical stripping process, and other transition metal chalcogenides are also suitable for use with the present invention. Of course, other methods of preparing a single layer of gravid dock or other transition metal chalcogenide compounds may also be used in the present invention.

The specific method for preparing the sample by the dry method comprises the following steps: 1) stripping the single-layer material from the crystal of the depressed disulfide by using a stripping adhesive tape through a mechanical stripping method to obtain a single-layer flaky sample on the adhesive tape;

2) and (3) pressing and transferring the single-layer sheet sample on the adhesive tape to a PDMS (polydimethylsiloxane) flexible substrate, wherein the surface with the sample is the upper surface, the surface without the sample is the lower surface, and the lower surface of the PDMS flexible substrate is fixedly adhered to one end of the glass carrier.

3) Fixing the other end of the glass carrier on a clamp holder of a left three-dimensional translation table, wherein the upper surface of the PDMS faces the ground;

4) placing and fixing a single-layer disulfide dock target substrate on a right three-dimensional translation stage, and adjusting the movement of an objective table to enable the target substrate to be positioned on a focal plane of an objective lens of a microscope, so as to find out a designated transfer area on the target substrate;

adjusting a left three-dimensional translation stage, moving a PDMS flexible substrate material attached with a single-layer disulfide dock to the position under the field of view of an objective, adjusting a translation stage shaft to move until a sample can be observed in the field of view of the objective, adjusting the position of an objective stage, enabling the pre-transferred single-layer disulfide dock sample to be over against a target chromium triselenide nanosheet substrate in the vertical direction, then adjusting the position of the objective stage until the target sample is contacted, taking out the transferred sample, and finding out a single-layer disulfide/chromium triselenide heterojunction dock sample under a microscope. Preferably, the thickness of the chromium diselenide nanosheet targeted by the present invention is in the range of 1.8-10 nm.

After optimization, the thickness of the chromium diselenide nanosheet in the single-layer disulfide dock/chromium diselenide heterojunction is below 10nm, and the surface is smooth and flat.

The invention relates to the application of a novel ultrathin chromium triselenide nanosheet magnetic material; and performing spectral test and analysis on the single-layer sulfur dock/chromium diselenide heterojunction by using a circular polarization test system.

The invention relates to the application of a novel ultrathin chromium triselenide nanosheet magnetic material; the chromium diselenide nanosheet is a novel ultrathin magnetic material, and the magnetic material is ultrathin, has good stability in atmospheric environment, higher Curie temperature and larger magnetic moment, and has a unique nanoscale self-spinning state. By constructing a single-layer disulfide dock/chromium diselenide heterojunction, the energy valley polarization of the single-layer disulfide dock can be regulated and controlled by utilizing a magnetic proximity effect, so that the application of a spin electronic device is promoted; the single-layer disulfide dock in the single-layer disulfide dock/chromium diselenide heterojunction can achieve 50% of energy valley polarization at low temperature, and has the advantages of no need of protection, stable work in atmospheric environment and obvious energy valley regulation and control.

Drawings

Fig. 1 is a schematic diagram of the growth of dichromium triselenide nanosheets of the present invention;

fig. 2 is an optical photograph of dichromium selenide nanosheets prepared in example 1 of the present invention;

FIG. 3 is an AFM image of dichromium triselenide nanosheets prepared in example 1 of the present invention;

FIG. 4a is a low power TEM photograph of dichromium selenide nanosheets prepared in example 1 of the present invention, with a 2 μm scale; FIG. 4b is a selected area electron diffraction picture; FIG. 4c is a TEM image of dichromium triselenide nanosheets with a 2 μm scale;

FIG. 5 is an EDX spectrum of the dichromium selenide nanosheets prepared in example 1;

FIG. 6 is a SEM photograph of chromium diselenide nanosheets prepared in example 1 and a mapping picture corresponding to the elements Cr and Se;

FIG. 7 shows the results of example 1 of the present invention at 300nm-SiO₂Magnetic measurement diagram of chromium triselenide nano-sheet grown on Si substrate;

fig. 8 is an optical photograph of dichromium selenide nanosheets prepared in example 2 of the present invention;

figure 9a is an optical photograph of a single layer of a dockerin disulfide/dichromium triselenide nanosheet heterojunction as prepared in example 3 of the present invention; FIG. 9b is a corresponding AFM image of the sample; figure 9c is a comparative spectrum of a single layer of dockerin disulfide and a single layer of dockerin disulfide/dichromium triselenide nanosheet heterojunction;

figure 10a is a valley polarization spectrum of single layer gravid dock of example 3 of the present invention; figure 10b is a valley polarization spectrum of a single layer of docusate/dichromium triselenide heterojunction nanosheet prepared;

FIG. 11 is an optical photograph of dichromium selenide nanosheets prepared in comparative example 1 of the present invention;

fig. 12 is an optical photograph of dichromium selenide nanosheets prepared in comparative example 2 of the present invention;

fig. 13 is an optical photograph of dichromium selenide nanosheets prepared in comparative example 3 of the present invention.

The equipment and growth environment relied on in the preparation process of the chromium diselenide nanosheet of the present invention can be seen in fig. 1.

The resultant flakes are seen in fig. 2 to be triangular or hexagonal in size, ranging from 20-60 um.

It can be seen from FIG. 3 that the synthesized flake has a flat surface with a thickness of 1.8nm, which is equivalent to the unit cell thickness.

The resulting flaky flake is a single crystal 2-dimensional structure as can be seen from fig. 4, which is a TEM picture, and the (110) plane lattice spacing is 0.3 nm; the selective electron diffraction result shows that the flaky flake has a good hexagonal lattice arrangement structure.

As can be seen from FIGS. 5 and 6, the detected spots of the obtained sheet-like chips contained two elements Cr and Se, and the ratio of the two elements Cr and Se obtained at the detected spots was determined to be 2: 3.

It can be seen from fig. 7 that the synthesized flake has a significant hysteresis loop characteristic under the action of the external magnetic field, indicating that the material has significant ferromagnetism at the temperature.

It can be seen from fig. 8 that the resultant flake is uniform and thin in thickness and has a size of 20-60 um.

As can be seen from fig. 9, the prepared single-layer docusate/chromium diselenide nanosheet has a clear heterojunction, the thickness of the upper single-layer docusate is about 0.7nm, and the thickness of the bottom chromium diselenide is about 7 nm. By comparing the fluorescence spectra of the single-layer disulfide dock and the single-layer disulfide dock/chromium diselenide nanosheet heterojunction, it can be seen that the spectrum of the heterojunction region is quenched, and the peak position has red shift.

From fig. 10, it can be seen that the heterojunction valley polarization spectrum of the single-layer disulfide dock/dichromium triselenide nanosheet prepared has great regulation and control, and the valley polarization value can reach 50%.

As can be seen from FIG. 11, the synthesized chromium diselenide nanosheet has a thickness close to that of a block body and a poor morphology.

It can be seen from fig. 12 that the synthesized material has irregular morphology and no dichromium triselenide nanosheet.

It can be seen from fig. 13 that the single-crystal dichromium triselenide nanosheets were not produced on the silicon wafer, and the silicon wafer was severely corroded.

The specific implementation mode is as follows:

the schematic diagram of the chemical vapor deposition device for preparing the dichromium selenide nanosheet magnetic material is shown in figure 1, wherein a quartz tube is provided with a tube furnace. The quartz tube comprises an upstream constant temperature area 1 and a central constant temperature area 2, and a porcelain boat 3 loaded with selenium powder is placed in the upstream constant temperature area of the tube furnace. The sodium chloride particles and the chromium powder are uniformly mixed according to the proportion of 1: 10, the mixed sodium chloride and chromium powder are placed in a porcelain boat 4, and the porcelain boat 4 is placed in the central area of the tube furnace. Mica or silicon substrate is placed right above the porcelain boat 4 with sodium chloride and chromium powder. The two ends of the quartz tube are both provided with air holes, wherein the air hole at the left end (carrier gas upstream) of the quartz tube is an air inlet hole, and the air hole at the right end of the quartz tube is an air outlet hole.

Example 1

Preparing chromium diselenide nanosheets:

placing the porcelain boat containing selenium powder in the upstream constant temperature region of the tube furnace, placing the porcelain boat containing mixed sodium chloride and chromium powder in the central constant temperature region (the substrate bottom is on the surface of the porcelain boat containing sodium chloride and chromium powder)₂Si, mica or a silicon substrate). The mass ratio of the sodium chloride particles to the chromium powder is 1: 10. 500sccm of high-purity argon gas was introduced into the quartz tube before heating, and the other gases in the tube were discharged while maintaining for 15 minutes, to ensure a stable growth atmosphere. The argon flow was then stabilized at 60sccm, the tube furnace heating temperature was again set to 850 ℃ for 25 minutes and the deposition was thermostatically carried out for 10 minutes at this temperature with the aid of a carrier gas. Finally, the sample is taken out after the isopipe furnace is naturally cooled to room temperature, and the deposition of the dichromium selenide nanosheet magnetic material on the substrate is confirmed through microscopic observationThe above. An experimental device diagram for preparing the chromium diselenide nanosheet is shown in fig. 1, an optical photo of the prepared chromium diselenide nanosheet is shown in fig. 2 (silicon is used as a substrate), and the optical photo shows that the synthesized chromium diselenide is in a uniform triangular or hexagonal shape and is 20-60um in size. Fig. 3 is an atomic force microscope picture of a typical single cell thickness sample, which is 1.8nm thick. SEM element mapping analysis showed that the detected spots of the obtained sheet contained two elements, Cr and Se, and the ratio of the two elements Cr and Se at the spots was 2: 3. The TEM image showed that the resulting flaky flakes were single-crystal 2-dimensional structures, and the (110) plane lattice spacings were 0.3nm, respectively. The selective electron diffraction result shows that the flaky flake has a good hexagonal lattice arrangement structure. FIG. 7 shows 300nm-SiO₂The parallel magnetic field scanning curve of the chromium diselenide grown on the Si substrate is tested at 3K. Under the action of an external magnetic field, the material has obvious hysteresis loop characteristics, which shows that the material has obvious ferromagnetism at the temperature.

Example 2

Compared with example 1, mica is used as a substrate, and the difference is that the mass ratio of the sodium chloride particles to the chromium powder is 1: 10. Before heating, the air in the quartz tube is exhausted by argon with larger flow, then the carrier gas is changed to argon flow of 60sccm, then a central heating temperature zone is set under argon atmosphere to be increased to 900 ℃ within 30 minutes, and constant-temperature deposition is carried out for 10min under the action of the temperature and the carrier gas. The single crystal chromium diselenide nanosheets are generated on the mica sheets. The optical diagram of the prepared dichromium triselenide nanosheet is shown in fig. 8. Relative to fig. 2, the samples synthesized on the mica substrate were regular in morphology and thinner in thickness.

Example 3

A single layer of the disulfide dock was peeled off the bulk crystal with tape by a mechanical peel method, and the peeled sample was then transferred to PDMS. After a target sample is found under an optical microscope, the target sample is transferred to a specific chromium diselenide nanosheet through a dry transfer method to form a single-layer depressed disulfide/chromium diselenide heterojunction, the thickness of the chromium diselenide nanosheet is below 10nm, and the surface of the chromium diselenide nanosheet is clean and flat. And (3) performing spectral test and analysis on the single-layer sulfur dock/chromium diselenide heterojunction by using a circular polarization test system. Figure 10a is the valley polarization spectrum of a single layer dockerin disulfide tested at 77K and figure 10b is the valley polarization spectrum of a single layer dockerin sulfide/chromium diselenide heterojunction tested at 77K. The comparison shows that the single-layer sulfur dock has fluorescence quenching in the heterojunction region, and the valley polarization spectrum shows larger regulation and control.

Comparative example 1

Compared with example 1, the effect of a higher deposition temperature was mainly studied with silicon as the substrate, as follows:

compared with the example 1, the difference is that the mass ratio of the sodium chloride particles to the chromium powder is 1: 10, and before heating, the air in the quartz tube is exhausted by argon with larger flow. Before heating, the air in the quartz tube is exhausted by argon with larger flow, then the carrier gas is changed to argon flow of 60sccm, then a central heating temperature zone is set under argon atmosphere to be heated to 950 ℃ within 30 minutes, and constant-temperature deposition is carried out for 10min under the action of the temperature and the carrier gas. There will be chromium diselenide formation on the silicon wafer close to the bulk material. The optical diagram of the prepared dichromium selenide thick plate is shown in figure 11.

Comparative example 2

Compared with example 1, the effect of a lower deposition temperature was mainly studied with silicon as the substrate, as follows:

compared with the example 1, the difference is that the mass ratio of the sodium chloride particles to the chromium powder is 1: 10, and before heating, the air in the quartz tube is exhausted by argon with larger flow. Before heating, the air in the quartz tube is exhausted by argon with larger flow, then the carrier gas is changed to argon flow of 60sccm, then a central heating temperature zone is set under argon atmosphere to be heated to 750 ℃ within 30 minutes, and constant-temperature deposition is carried out for 10min under the action of the temperature and the carrier gas. Only granular form on the silicon wafer, no chromium diselenide.

Comparative example 3

Compared with example 1, the influence of the raw materials is mainly discussed by using silicon as a substrate, and the specific details are as follows:

compared with example 1, the difference is that CrCl is used₂As starting material, CrCl₂The mass ratio of Se powder to Se powder is 1: 1.5. Before heating, the air in the quartz tube is exhausted by argon with larger flow. Then heating the central temperature region to 850-900 ℃ under the atmosphere with the Ar flow rate of 60 sccm. The temperature of the temperature zone (deposition temperature) is maintained, and deposition is carried out for 10min at constant temperature under the action of the temperature and carrier gas. No single-crystal dichromium triselenide nanosheet is generated on the silicon wafer, the silicon wafer is severely corroded, and the optical diagram is shown in fig. 13.

The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.