WO2020082223A1

WO2020082223A1 - Black phosphorus-like ultra-thin bismuth nano-sheet modified compound film and preparation method therefor

Info

Publication number: WO2020082223A1
Application number: PCT/CN2018/111346
Authority: WO
Inventors: 王干; 陈俊树; 何洪涛; 叶飞; 梅佳伟; 周良; 王琳晶
Original assignee: 南方科技大学
Priority date: 2018-10-23
Filing date: 2018-10-23
Publication date: 2020-04-30
Also published as: CN112689609A

Abstract

A black phosphorus-like ultra-thin bismuth nano-sheet modified compound film and a preparation method therefor. The compound film comprises a base film and a black phosphorus-like bismuth nano-sheet intercalation in the base film. Realizing large-scale synthesis of a black phosphorus-like two-dimensional bismuth material and control of physical properties of the material provides a viable path for industrial use of a black phosphorus-like bismuth material for controlling physical properties of materials such as magnetism and semiconductivity, expanding the field of use for metallic bismuth.

Description

Composite film modified by black phosphorus phase ultra-thin bismuth nanosheets and preparation method thereof

Technical field

The present disclosure relates to the technical field of material preparation, for example, to a composite film modified by a black phosphorus phase ultra-thin bismuth nanosheet and a preparation method thereof.

Background technique

Molecular beam epitaxy is a thin-film growth technology that epitaxially grows high-quality single crystal thin films or superlattice structures on single crystal substrates. The technology was born in Bell Laboratories in the 1960s. (Cho, AY; Arthur, JR; Jr (1975). "Molecular beam epitaxy". Prog. Solid State Chem. 10: 157-192.) Because this molecular beam epitaxy growth technology can be realized in an ultra-high vacuum environment Atomic-level wafer-level semiconductor thin film growth, therefore, is widely used in high-quality semiconductor optoelectronic chips, high mobility field effect transistors, cascade lasers and other semiconductor technology industries, resulting in significant economic value. In addition, the molecular beam epitaxy technology is used to achieve cutting-edge scientific research such as the giant magnetoresistive effect, the fractional quantum Hall effect, and the inverse constant quantum Hall effect, which directly gave birth to several Nobel Prize-level research achievements. (①McCray, WP (2007). "MBE Deserves a Place in the History Books". Nature Nanotechnology. 2 (5): 259-261., ②H.

S. Strite, GBGao, MELin, B. Sverdlov, and M. Burns. "Large-band-gap SiC, III-V nitride, and II-VI ZnSe-based semiconductor device technologies". Journal of Applied Physics 76, 1363 ( 1994)., ③ M.Z. Hasan and CLKane. "Colloquium: Topological insulators". Rev. Mod. Phys. 82, 3045., and ④ Wanjun Jiang, Gong Chen, Kai Liu, Jiadong Zang, Suzanne GEte Velthuis, Axel Hoffmann. "Skyrmions in magnetic multilayers". Physics Reports 704 (2017) 1-49) In recent years, with the breakthrough of graphene and other two-dimensional materials, molecular beam epitaxy technology has also emerged in the research of such two-dimensional semiconductor electronic materials. It is widely used by researchers and industry to realize the technical application of epitaxial growth of two-dimensional semiconductor thin films with precise atomic layers.

Bismuth (Bi) is a non-toxic and stable heavy element (atomic number 83). In actual life, bismuth is mainly used in the pharmaceutical and other industrial fields. Under normal pressure, elemental bismuth has a layered structure with hexagonal symmetry and the electrical properties of metals. In 2004, Japanese research scholar Nagao et al published a paper in the Physical Review Letters and found that bismuth atoms under the thickness of four atomic layers, due to the reconstruction of atomic bonds, will form a kind of black phosphorus phase The physical structure of the diatomic layered structure has also been significantly changed. (T. Nagao, JTSadowski, M. Saito, S. Yaginuma, Y. Fujikawa, T. Kogure, T. Ohno, Y. Hasegawa, S. Hasegawa, and T. Sakurai. “Nanofilm” Allotrope and Phase Transformation Transformation of Ultrathin Bi Film (Si) (Phys. Rev. Lett. 93 (2004) 105501.) Black phosphorus phase bismuth is a two-dimensional layered bismuth material that will only appear in the initial stage of film growth, further electronic structure research It is shown that this black phosphorus phase bismuth layer material is a new type of semiconductor material and has remarkable spintronic properties. (Shin YAGINUMA et al. "Electronic Structure of Ultrathin Bismuth Films with A7 and Black-Phosphorus-like Structures". Journal of the Physical Society of Japan Japan 77 (2008) 014701.) However, although as early as 2004, people have already determined The existence of such two-dimensional material of black phosphorus phase bismuth, but due to its extremely harsh epitaxial growth conditions and low stability, scientists cannot achieve a controlled large amount of epitaxial growth of black phosphorus phase bismuth structure, and it only grows On the surface of the material, this significantly hindered the further research and use of this allotrope of bismuth.

Summary of the invention

The present disclosure provides a black phosphorus phase ultra-thin bismuth nanosheet modified composite film and a preparation method thereof.

In an embodiment of the present disclosure, a black phosphorus phase bismuth nanosheet modified composite film is provided. The composite film includes a base film and a black phosphorus phase bismuth nanosheet interposed in the base film.

The composite film of the present disclosure is a crystalline film, in which the base film and the black phosphorus phase bismuth nanoplate are both of a crystal structure. The composite film of the present disclosure is clearly different from the prior art. Although there are a small amount of black phosphorus phase bismuth nanomaterials in the prior art, they are all formed on the surface in a small amount, and there is no intercalation type structure. The composite film of the present disclosure is black The large-scale preparation of phosphorus phase bismuth nanosheets and the application of interlayer doping modification to realize the application of matrix films (such as semiconductors, insulating materials or metal conductors, etc.) are of great significance.

The formation of the composite film of the present disclosure involves not only the preparation of black phosphorus phase bismuth nanosheets, but also the doping modification of the base film.

In an embodiment, the base film includes any one of a conductor, a semiconductor, or an insulator. The conductor may be, for example, a metal / semi-metal, specifically a metal elemental or alloy thin film such as Fe, Co, Cr, or FeCr, a CrTe compound such as CrTe, Cr ₂ Te ₃ , Cr ₃ Te _4, or Cr ₅ Te ₈ ; a semiconductor may, for example, is ZnSe, ZnTe, ZnS and other group II-VI semiconductors, GaN and other group III-V semiconductors, or MoTe _{_{_2,}} MoSe _2, MoS ₂ and the like of the two-dimensional transition metal chalcogenide (TMDCs). However, it is not limited to the above-mentioned base films, and other base films commonly used in the art that can achieve the same technical effect can also be used in the technical solutions of the present disclosure.

In one embodiment, the base film is any one of metal element, alloy thin film, CrTe compound, group II-VI semiconductor, group III-V semiconductor, or two-dimensional transition metal chalcogenide compound.

In one embodiment, the base film is chromium telluride.

In an embodiment, based on the surface area of the composite membrane as 100%, the percentage surface area of the black phosphorus phase bismuth nanosheets is 5% -15%, such as 5%, 7%, 8%, 10%, 11 %, 12%, 13%, 14% or 15%, etc.

In one embodiment, the thickness of the black phosphorus phase bismuth nanoplate is a double layer of black phosphorus phase bismuth.

In an embodiment, the thickness of the black phosphorus phase bismuth nanoplates is 0.5 nm to 0.7 nm, such as 0.5 nm, 0.52 nm, 0.53 nm, 0.55 nm, 0.58 nm, 0.6 nm, 0.63 nm, 0.66 nm, 0.68 nm Or 0.7nm, etc.

In an embodiment, the composite film is located on a substrate, and the disclosure does not limit the type of the substrate, for example, it may be a wafer substrate.

In one embodiment, the composite film is prepared as follows: during the epitaxial growth of the base film, a thermal evaporation source of bismuth is introduced to produce a beam of bismuth atoms, and Bi atoms are deposited to form a black phosphorus phase bismuth nanosheet, and The black phosphorus phase bismuth nanoplates are buried in the base film as the base film grows, thereby forming a composite film.

In one embodiment of the present disclosure, a method for preparing the composite film modified with black phosphorus phase bismuth nanosheets is provided. The method includes the following steps:

In the process of growing the base film on the substrate, a thermal evaporation source of bismuth element is passed to produce a beam of bismuth atoms. As the base film grows, Bi atoms are deposited to form a black phosphorus phase bismuth nanoplate, and the black phosphorus phase bismuth nanoplate As the base film grows, it is buried in the base film to form a composite film on the substrate;

In the process of preparing the composite film, the substrate temperature is controlled at 200 ° C to 400 ° C, for example, 200 ° C, 220 ° C, 240 ° C, 260 ° C, 280 ° C, 300 ° C, 325 ° C, 350 ° C, 370 ° C, 380 ℃ or 400 ℃, if the temperature is lower than 200 ℃, it will cause the composite film to be amorphous; if the temperature is higher than 400 ℃, Bi atoms will not be deposited due to evaporation to form black phosphorus phase bismuth nanoplates.

The method of the present disclosure can realize a large amount of synthesis and intercalation application of black phosphorus phase bismuth nanosheets by opening the bismuth source during the growth of the thin film. The dual goal of regulating physical properties is to solve the technical problem that black phosphorus phase bismuth nanosheets are difficult to prepare in large quantities and the technical problem of application.

In one embodiment, the method of epitaxially growing the base film is: a method of molecular beam epitaxial growth.

In the method of the present disclosure, the type of the substrate is not limited, for example, it may be a wafer substrate.

In an embodiment of the method, the base film includes any one of a conductor, a semiconductor, or an insulator, preferably a metal / half metal, a group II-VI semiconductor, a group III-V semiconductor, or a two-dimensional transition metal Any one of the chalcogenide compounds.

In an embodiment of the method, the base film is any one of a metal element, an alloy thin film, a CrTe compound, a group II-VI semiconductor, a group III-V semiconductor, or a two-dimensional transition metal chalcogenide compound.

In an embodiment of the method, the base film is a chromium telluride film.

In one embodiment, the temperature of the thermal evaporation source that evaporates to produce bismuth element is controlled at 450 ° C to 650 ° C, such as 450 ° C, 475 ° C, 500 ° C, 520 ° C, 550 ° C, 570 ° C, 580 ° C, 600 ° C, 625 ℃ or 650 ℃ etc.

In one embodiment, the temperature of the thermal evaporation source that produces bismuth by evaporation is controlled at 450 ° C to 550 ° C, and within this range of 450 ° C to 650 ° C, a stable vapor pressure can be formed to produce a stable Bi beam flow, thereby The structure of the interlayer substrate film of the black phosphorus phase bismuth nanosheets is well formed.

In one embodiment, the bismuth atomic beam current can be adjusted by adjusting the temperature of the thermal evaporation source of the bismuth element, and the size and density of the black phosphorus phase bismuth nanoplates can be adjusted. Flow into a positive correlation.

In one embodiment, the substrate film is a chromium telluride film, and when the chromium telluride film is grown, the temperature of the chromium source is controlled at 900 ° C to 1200 ° C, for example, 900 ° C, 925 ° C, 950 ° C, 980 ° C, 1000 ° C, 1050 ℃, 1100 ℃, 1150 ℃ or 1200 ℃, etc .; control tellurium source temperature at 300 ℃ ~ 400 ℃, such as 300 ℃, 325 ℃, 350 ℃, 370 ℃, 380 ℃, 390 ℃ or 400 ℃.

In an embodiment, the method includes the following steps:

Using the molecular beam epitaxial growth method, the chromium source, tellurium source and bismuth element thermal evaporation source are simultaneously passed into the epitaxial growth equipment to control the chromium source temperature at 900 ℃ ~ 1200 ℃, tellurium source temperature at 300 ℃ ~ 400 ℃, evaporation produced The temperature of the thermal evaporation source of bismuth element is 450 ℃ ～ 550 ℃, and the substrate temperature is 200 ℃ ～ 400 ℃. As the base film grows, Bi atoms deposit to form black phosphorus phase bismuth nanoplates, and the black phosphorus phase bismuth nanoplates follow The growth of the base film is buried in the base film, thereby forming a composite film on the substrate.

Compared with the related art, the embodiments of the present disclosure achieve the first efficient preparation of stable black phosphorus phase bismuth nanoplates. In one embodiment of the present disclosure, a specially designed molecular beam epitaxial growth process is used to realize the first large-scale and efficient preparation of black phosphorus phase bismuth two-dimensional ultra-thin nanosheets, and the percentage surface area of the resulting black phosphorus phase bismuth nanosheets can reach 15 %.

In the embodiments of the present disclosure, the dual goals of synthesizing a large number of black phosphorus phase bismuth nanosheets and regulating the physical properties of the material (matrix film) are achieved. For the first time, a large number of black phosphorus phase bismuth two-dimensional materials are synthesized and applied to Cr ₂ Te ₃ In the case of medium-doped black phosphorus phase bismuth, the black phosphorus phase bismuth nanosheets were intercalated into a magnetic film such as chromium telluride (Cr ₂ Te ₃ ), and the physical properties of the chromium telluride magnetic film were successfully adjusted, such as By controlling the magnetic domains of magnetic materials, the topological magnetic structure of stigmine is generated, and the controllable preparation of magnetic stigmine is realized.

The method of the embodiment of the present disclosure can realize the doping of thin films such as semiconductors, insulators or metal conductors with black phosphorus phase nanosheets, and the resulting composite film has broad application prospects:

The black phosphorous phase bismuth nanosheets in the composite film formed in the embodiments of the present disclosure have an ultra-thin thickness, and the growth technology of the black phosphorous phase bismuth nanosheets is compatible with the epitaxial growth process of other semiconductor insulators, metals, and other thin films. The described growth process of black phosphorus phase bismuth nanosheets can be extended to other thin film growth processes, which can produce more abundant physical property control applications.

The present disclosure provides a feasible route for the industry to use black phosphorus phase bismuth materials to control the properties of magnetic, semiconductor and other materials, and is expected to greatly expand the application field of bismuth metal.

BRIEF DESCRIPTION

The drawings are used to provide a further understanding of the technical solutions of the present disclosure, and form a part of the specification, and are used to explain the technical solutions of the present disclosure together with the embodiments of the present application, and do not constitute limitations on the technical solutions of the present disclosure.

FIG. 1a is a schematic diagram of an apparatus for growing a black phosphorus phase Bi nanosheet according to an embodiment of the present disclosure, wherein, 1-evaporation source, 2-heating coil, 3-electron gun, 4-substrate, 5-beam current monitoring, 6-ion gauge , 7-low temperature panel, 8-RHEED screen;

FIG. 1b is an electron diffraction pattern monitored during film growth according to an embodiment of the present disclosure;

1c is a cross-sectional high-angle annular dark field (HAADF) scanning transmission electron microscope image of a chromium telluride film doped with black phosphorus phase bismuth nanoplates provided by an embodiment of the present disclosure;

Figure 1d is a cross-sectional high-angle annular dark field (HAADF) scanning transmission electron microscope image of a bismuth nanosheet (corresponding to the bright line in the ellipse on the right) of Figure 1c;

Figure 1e is a first-principles calculation of the atomic structure of the black phosphorus phase bismuth nanosheet intercalation (also known as embedding) into the chromium telluride crystal lattice, where 1 represents tellurium atoms and 2 represents chromium atoms, 3 represents bismuth atom;

2a is a schematic diagram of the generation of stigmine intercalated in a chromium telluride film of a black phosphorus phase bismuth nanosheet according to an embodiment of the present disclosure;

2b is a calculation simulation result of the change of the stigmine intercalated in the chromium telluride of the black phosphorus phase bismuth nanosheet according to an embodiment of the present disclosure with the applied magnetic field;

2c and 2d are schematic diagrams of the regulation of stigmine using STM needle tip according to an embodiment of the present disclosure;

Figure 2e is the mechanism of regulation described in Figure 2c and Figure 2d.

Specific examples

The technical solutions of the present disclosure will be further described below with reference to the drawings and through specific implementations.

In the process of using molecular beam epitaxy to grow substrate films such as semiconductors, insulators or metal conductor films, at the same time, the thermal evaporation source of bismuth element (the temperature of the evaporation source is controlled between 450-650 degrees) is opened to provide a beam of Bi, At the same time, the substrate temperature is controlled between 200-400 ℃, Bi atoms will be deposited on the sample surface to form a bismuth black phosphorus phase nanosheet structure and buried in the material as the material grows, as the growth process continues, A large number of black phosphorus phase bismuth nanosheet intercalation structures will be embedded inside the grown film, thereby achieving the dual goals of a large amount of synthesis of black phosphorus phase bismuth and material property control.

Example 1

Molecular beam epitaxy method of black phosphorus phase bismuth nanosheets

Here, taking the epitaxial growth of chromium telluride thin film as an example, the technical route is described. The epitaxial growth method described here can not only modify and modify bismuth nanoplatelets of chromium telluride, but also apply to the modification of bismuth nanoplatelets of other semiconductors, insulators, conductors and other thin films.

In one embodiment, the evaporation source of chromium and tellurium is heated, and the temperature of the chromium source is controlled between 900-1200 degrees Celsius, and the temperature of the tellurium source is controlled between 300-400 degrees Celsius. At the same time, the bismuth evaporation source furnace is turned on And the temperature of the bismuth evaporation source furnace is controlled between 450-650 degrees Celsius, and the substrate temperature is adjusted between 200-400 degrees Celsius. As the epitaxial growth proceeds, a chromium telluride film will be epitaxially grown on the surface of the wafer. At the same time, since the bismuth atom will not form a stable compound with the chromium or tellurium element, it will diffuse on the surface of the film, free, and then It will be deposited on the surface of the sample and form a bismuth black phosphorus phase double-layer structure, and will be buried in the material as the material grows, forming many black phosphorus phase bismuth / chromium telluride heterojunction interfaces inside the film, thus changing The physical properties of the material, the black phosphorus phase nanosheets are intercalated in the chromium telluride film.

In one embodiment, by adjusting the evaporation temperature of the bismuth source and further adjusting the bismuth atomic beam current, the size and density of the black phosphorus phase bismuth nanoplates can be effectively controlled, thereby effectively controlling the ferromagnetic properties of chromium telluride.

Figure 1a is a schematic diagram of a device for growing black phosphorus phase Bi nanosheets, where 1-evaporation source, 2-heating coil, 3-electron gun, 4-substrate, 5-beam monitoring, 6-ion gauge, 7-low temperature Panel, 8-RHEED screen. During the epitaxial growth of the chromium telluride thin film, the three thermal evaporation sources of Cr, Te, and Bi are simultaneously turned on and adjusted to the temperature described above, and the corresponding atoms are sprayed onto the surface of the gallium arsenide semiconductor wafer to perform the black phosphorus phase The epitaxial growth of bismuth nanoplates.

Figure 1b is the electron diffraction pattern monitored during the film growth process. The electron diffraction pattern shows that the black phosphorus phase bismuth nanosheet / chromium telluride composite film grown by the above molecular beam epitaxy method has high quality surface flatness and Lattice perfection.

Figure 1c is a cross-sectional high-angle annular dark field (HAADF) scanning transmission electron microscope image of a chromium telluride film doped with black phosphorus phase bismuth nanoplates. In the figure, white bright lines (such as ellipses) appear inside the chromium telluride lattice. The bright line in the area) is the black phosphorus phase bismuth nanoplate.

Figure 1d is a high-angle annular dark field (HAADF) scanning transmission electron microscope image of the cross-section of a bismuth nanosheet (corresponding to the bright line in the ellipse on the right) in FIG. 1c. Bismuth atoms with higher brightness constitute a The two-dimensional structure of the black phosphorus phase, the figure also shows that the black phosphorus phase bismuth nanoplates are chromium telluride atoms above and below, forming a black phosphorus phase bismuth nanoplate / chromium telluride composite interface.

Figure 1e is a first-principles calculation of the atomic structure of the black phosphorus phase bismuth nanosheet intercalation (also known as embedding) into the chromium telluride crystal lattice, where 1 represents tellurium atoms and 2 represents chromium atoms, 3 represents the bismuth atom, indicating that the black phosphorus phase bismuth nanoplates will interact with the chromium telluride lattice at the electronic level.

The foregoing FIGS. 1 a to 1 e show a schematic diagram of a growth method of black phosphorus phase bismuth nanoplates and a structure characterization structure, illustrating that the method of the present disclosure can effectively synthesize black phosphorus phase bismuth nanoplates.

In one embodiment of the present disclosure, the application principle of black phosphorus phase bismuth nanosheets is provided:

Figure 2a is a schematic diagram of the generation of stigmine intercalated in the chromium telluride film of the black phosphorus phase bismuth nanosheet. As shown in FIG. 2a, the chromium telluride film doped with the black phosphorus phase bismuth has a strong bismuth atom. The spin-orbit coupling effect, the magnetic interaction of the interface will cause the topological magnetic stigmine to be produced at the interface of the bismuth double layer and chromium telluride. Therefore, the chromium telluride film becomes intercalated after the black phosphorus phase bismuth nanosheet Get the Sigmar material.

Figure 2b is the calculated simulation results of the change of the stigmine intercalated in the chromium telluride of the black phosphorus phase bismuth nanosheets with the applied magnetic field. In the case of the applied field H = 0.46-1.0 Tesla, the chromium telluride is formed. For the stigmine array, the diameter of each stigmine is determined by the size of the black phosphorus phase bismuth nanoplates. It can also be found that when a magnetic field is provided, the material vortexes, with and without vortex, the 0, 1 in the information can be seen.

According to the report of Fert et al., We can regulate each stigmine by the tip of the scanning tunnel microscope (Albert, Fert, Nicolas, Reyren, and Vincent, Cros. "Magnetic skyrmions: advances, physics, and potential applications". NATURE REVIEWS, MATERIALS 2 (2017 ) 17031. And Niklas Romming, Christian Hanneken, Matthias Menzel, Jessica E. Bickel, Boris Wolter, Kirsten von Bergmann, Andr Kubetzka, Roland Wiesendanger. "Writing and Deleting Singles Magnetic Vol. 2013,". Figures 2c and 2d are schematic diagrams of the regulation of stigmine using the STM tip; Figure 2e is the mechanism of regulation described in Figures 2c and 2d. The regulation mechanism of Figure 2e is to change the ferromagnetic state and magnetic field by applying a voltage The electrons of the gemingon state interact with each other a month ago, thereby creating or eliminating a skyming son there. As shown in Figures 2c-2e, data can be written and deleted by adjusting the voltage of the tip and the surface of the material to change the number of electrons in the ferromagnetic state and the stigmine state. The chromium telluride magnetic storage device based on the intercalation of black phosphorus phase bismuth nanosheets realized by this method can contain about 5TB of information in a square centimeter square film, which has an increased capacity compared to the current Blu-ray DVD More than a hundred times.

2a-2e show simulation diagrams of the topological magnetic structure of strimine produced by Cr ₂ Te ₃ doped with black phosphorus phase bismuth, illustrating that the present disclosure can not only synthesize a large amount of black phosphorus phase bismuth nanoplates, but also achieve Cr ₂ Te _3. The doping of ₃ realizes physical property control and realizes its application.

The applicant declares that the present disclosure illustrates the detailed method of the present application through the above-mentioned embodiments, but the present disclosure is not limited to the detailed method, that is, it does not mean that the disclosed method must rely on the detailed method to be implemented. Those skilled in the art should understand that any improvement to the present disclosure, equivalent replacement of various raw materials of the disclosed product, addition of auxiliary components, choice of specific methods, etc., fall within the scope of protection and disclosure of the present disclosure.

Claims

A composite film modified by black phosphorus phase bismuth nanosheets, the composite film includes a base film and a black phosphorus phase bismuth nanosheet interposed in the base film.
The composite film according to claim 1, wherein the base film includes any one of a conductor, a semiconductor, or an insulator.
The composite film according to claim 2, wherein the base film is any one of metal / semimetal, group II-VI semiconductor, group III-V semiconductor, or two-dimensional transition metal chalcogenide compound.
The composite film according to claim 3, wherein the base film is any one of a metal element, an alloy thin film, a CrTe compound, a II-VI semiconductor, a III-V semiconductor, or a two-dimensional transition metal chalcogenide compound Species.
The composite film according to claim 4, wherein the base film is chromium telluride.
The composite membrane according to any one of claims 1 to 5, wherein the percentage surface area of the black phosphorus phase bismuth nanosheets is 5% to 15% based on the surface area of the composite membrane being 100%.
The composite film according to any one of claims 1 to 6, wherein the thickness of the black phosphorus phase bismuth nanoplate is a double layer of black phosphorus phase bismuth.
The composite film according to any one of claims 1 to 7, wherein the black phosphorus phase bismuth nanoplate has a thickness of 0.5 nm to 0.7 nm.
The composite film according to any one of claims 1 to 8, wherein the composite film is located on a substrate.
A method for preparing a composite film modified with black phosphorus phase bismuth nanosheets according to any one of claims 1-9, the method comprising the following steps:

In the process of epitaxial growth of the base film on the substrate, a thermal evaporation source of bismuth element is passed to produce a beam of bismuth atoms. As the base film grows, Bi atoms are deposited to form black phosphorus phase bismuth nanoplates, and the black phosphorus phase bismuth nanometers The sheet is buried in the base film as the base film grows, thereby forming a composite film on the substrate;

During the preparation of the composite film, the substrate temperature is controlled at 200 ° C to 400 ° C.
The method according to claim 10, wherein the method of epitaxially growing the base film is a method of molecular beam epitaxial growth.
The method according to claim 10 or 11, wherein the base film includes any one of a conductor, a semiconductor, or an insulator.
The method according to claim 12, wherein the base film is any one of a metal / semi-metal, a group II-VI semiconductor, a group III-V semiconductor, or a two-dimensional transition metal chalcogenide compound.
The method according to claim 13, wherein the base film is any one of a metal element, an alloy thin film, a CrTe compound, a group II-VI semiconductor, a group III-V semiconductor, or a two-dimensional transition metal chalcogenide compound .
The method according to claim 14, wherein the base film is a chromium telluride film.
The method according to claim 10, wherein the temperature of the thermal evaporation source that evaporates to produce bismuth element is controlled at 450 ° C to 650 ° C.
The method according to claim 16, wherein the temperature of the thermal evaporation source that evaporates to produce bismuth element is controlled at 450 ° C to 550 ° C.
The method according to any one of claims 10 to 17, wherein the bismuth atomic beam current is adjusted by adjusting the temperature of the thermal evaporation source of the bismuth element, thereby adjusting the size and density of the black phosphorus phase bismuth nanoplates.
The method according to any one of claims 10 to 18, wherein the base film is a chromium telluride film, and when the chromium telluride film is grown, the chromium source temperature is controlled at 900 ° C to 1200 ° C, and the tellurium source temperature is controlled at 300 ℃ ～ 400 ℃.
The method according to any one of claims 10-19, wherein the method comprises the following steps:

Using the molecular beam epitaxial growth method, the chromium source, tellurium source and bismuth element thermal evaporation source are simultaneously passed into the epitaxial growth equipment to control the chromium source temperature at 900 ℃ ~ 1200 ℃, tellurium source temperature at 300 ℃ ~ 400 ℃, evaporation The temperature of the thermal evaporation source of bismuth element is 450 ℃ ～ 550 ℃, and the substrate temperature is 200 ℃ ～ 400 ℃. As the base film grows, Bi atoms deposit to form black phosphorus phase bismuth nanoplates, and the black phosphorus phase bismuth nanoplates follow The growth of the base film is buried in the base film, thereby forming a composite film on the substrate.