WO2020223922A1

WO2020223922A1 - Heterojunction structure material, preparation method therefor and use thereof

Info

Publication number: WO2020223922A1
Application number: PCT/CN2019/085984
Authority: WO
Inventors: 李彬; 王干; 张润楠; 王琳晶
Original assignee: 南方科技大学
Priority date: 2019-05-08
Filing date: 2019-05-08
Publication date: 2020-11-12

Abstract

A heterojunction structure material, a preparation method therefor and use thereof. The heterojunction structure material comprises n layers of stacking units, each stacking unit comprising a reduced material layer and a metal compound layer attached to the reduced material, N being greater than or equal to 1. The preparation method for the hetrojunction structure material comprises the following steps: growing a reduced material; depositing an elemental metal on the surface of the reduced material; and repeating the process of growing the reduced material and depositing an elemental metal on the upper surface of the reduced material for n-1 times to obtain the hetrojunction structure material.

Description

Heterojunction structure material, and preparation method and application thereof

Technical field

This application belongs to the field of new functional electronic devices, for example, relates to a heterojunction structure material, and a preparation method and application thereof.

Background technique

Because the heterojunction structure has abundant interface effects, it can realize electronic devices with multiple functions. For example, the chromium-based metal compounds mentioned in this application have rich magnetic properties, and the heterojunction structure formed by magnetic thin film materials and other materials has very important application value in current and future electronic devices. In 2007, Nobel The discovery of the giant magnetoresistance effect awarded by the award is one of the examples. Now the giant magnetoresistance effect has been widely used in the magnetic storage industry and has produced huge industrial value.

For another example, with the rise of topological materials research hotspots in recent years, heterojunctions based on topological materials have also become one of the hotspots in frontier research fields. Among them, the representative is the research on the heterogeneous interface between ferromagnetic materials and topological insulators. Topological insulators, because of their topologically non-trivial electronic structure, exhibit the unique characteristics of internal insulation and surface conduction. The conductive electrons on the surface can be called Dirac electrons because of the linear Dirac cone dispersion relationship. The quantum state of this Dirac electron is protected by time reversal symmetry, and magnetism can just destroy this. A symmetry, so the heterogeneous structure of topological insulators and magnetic materials can bring very rich physical effects, such as evidence of the existence of magnetic skyrmions. In this material system, magnetic skyrmions may play a key role in the future information industry. Therefore, it is particularly important to prepare high-quality heterojunction structures.

CN102586733A discloses a Ti _0.57 Cr _0.43 N/p-Si heterostructure with room temperature magnetoresistance effect and a preparation method. The preparation method includes the following steps: using a DPS-III type ultra-high vacuum opposed target magnetron sputtering coating machine, uniformly placing Cr sheets on the surface of the Ti target, and removing the p-type Si (100) single wafer on the substrate rack The temperature rises to 550°C at a rate of 10°C/s. A current of 0.2A and a DC voltage of 1050V are applied to a pair of Ti targets, pre-sputtering for 15 minutes, and the sputtering current and voltage are stable; The baffle plate began to sputter, and the position of the p-type Si (100) single wafer was fixed; the film deposition time was 15 minutes, and the Ti _0.57 Cr _0.43 N/p-Si heterostructure was obtained. In the preparation of the method, a relatively violent chemical reaction occurs during the preparation process, resulting in a higher surface roughness and a lower flatness of the obtained heterojunction, and the superlattice structure cannot be prepared.

CN107585747A discloses a chalcogen compound heterojunction magnetic nano material and a preparation method thereof. After mixing Mn, Cr, and Te, in an inert gas environment, reacting at a temperature of 350-400°C, the chemical formula is (1～2x ) MnTe/xCr ₂ Te ₃ chalcogen compound heterojunction magnetic nanomaterial. The chalcogenide compound heterojunction magnetic nanomaterial has a rod-like structure with an antiferromagnetic MnTe rod body and a ferromagnetic Cr ₂ Te ₃ cap body, and a heterojunction is formed between MnTe and Cr ₂ Te ₃ , The mass junction interface is small, the uniformity is poor and the flatness is low.

Therefore, there is a need in the art to develop a new type of heterojunction structure material that has good interface clarity and can grow superlattice structures repeatedly. The preparation process is simple, the prepared heterojunction interface has good flatness, and is easy for industrial production.

Summary of the invention

The following is an overview of the topics detailed in this article. This summary is not intended to limit the scope of protection of the claims.

The present application provides a heterojunction structure material. The heterojunction structure material includes n layers of superimposed units, each of the superimposed units includes a reduced material layer and a metal compound layer attached to the reduced material layer , Where n≥1, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, or 50.

In the heterojunction structure material described in this application, a heterojunction is formed between the reduced material layer or the intermediate product layer and the metal compound layer, and the heterojunction interface has high definition; at the same time, the reduced material layer or the intermediate product layer is used The multilayer structure alternately arranged with the metal compound layer can realize multiple functional interfaces or channels in a single material, which greatly improves product efficiency.

There may also be an intermediate product layer between the reduced material layer and the metal compound layer described in this application. The intermediate product layer is a layer formed by the reduced metal in the reduced material layer or the reduced metal and the reduced metal Multi-element compound formed by combining raw materials.

In one embodiment, n≥2.

In an embodiment, the n≥3.

In an embodiment, the n≥10.

In an embodiment, the metal compound includes a chromium-based metal compound, and the chromium-based metal compound includes any one or a combination of at least two of chromium sulfide, chromium selenide, and chromium telluride.

The chemical formulas of chromium sulfide, chromium selenide and chromium telluride mentioned in this application are not limited to Cr ₂ S ₃ , CrSe and Cr ₂ Te ₃ , and the molar ratio between the elements in the metal compound is not specifically limited, and only contains sulfur. And chromium can be called chromium sulfide, only containing selenium and chromium can be called chromium selenide, and only containing tellurium and chromium can be called chromium telluride.

Because of the good magnetic properties of chromium-based metal compounds, the heterojunction formed with the reduced material has rich physical effects. Especially in chromium telluride, the average magnetic moment of each chromium atom can reach 1.98μB, which is The temperature inside can reach room temperature.

In one embodiment, in each of the overlapping units, the average thickness of the metal compound layer is 1.5-9 nm, for example, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, or 8 nm.

This application does not specifically limit the thickness of the metal compound layer, and those skilled in the art can adjust it according to actual needs. In this application, it can be 1.5-9 nm.

In one embodiment, in each of the superimposed units, the average thickness of the reduced material layer is 6-18nm, for example, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm or 17nm. Wait.

This application does not specifically limit the thickness of the reduced material layer, and those skilled in the art can adjust it according to actual needs. In this application, it can be 6-18 nm.

In one embodiment, the reduced material includes any one or a combination of at least two of sulfide, selenide, and telluride.

In one embodiment, the reduced material includes any one or a combination of at least two of metal sulfides, metal selenides, and metal tellurides. The reducibility is weaker than that of chromium.

In an embodiment, the reduced material includes any one or a combination of at least two of bismuth telluride, molybdenum sulfide, and zinc selenide.

This application provides a method for preparing a heterojunction structure material, including:

Growth of reduced materials;

Depositing elemental metal on the upper surface of the reduced material;

Repeat the process of growing the reduced material and depositing elemental metal on the upper surface of the reduced material n-1 times to obtain a heterojunction structure material.

This application utilizes the strong reducibility of the elemental metal to reduce the metal element in the reduced material and react with the non-metal element to form a metal compound, thereby forming a heterojunction structure between the metal compound and the reduced material or intermediate product; At the same time, the preparation method of the present application can prepare a multilayer structure, and can obtain a superlattice structure material.

In the related art, a method in which metal elements and non-metal elements enter the chamber for deposition to generate metal compounds is adopted. This application adopts a method of preparing metal compounds by reduction. The growth temperature of the metal compounds is relatively low, and the reduced materials are not easily thermally decomposed. Mass-junction structure materials have better performance.

In one embodiment, growing the reduced material includes: growing the reduced material by epitaxial deposition or single crystal growth.

In one embodiment, when the growth method of the reduced material is epitaxial deposition, the source temperature of the epitaxial deposition is the evaporation temperature or sublimation temperature of the reduced material. In one embodiment, it is the evaporation temperature or sublimation temperature of the reduced material. The partial pressure of the material reaches a temperature of 10 ^-6 mbar in an ultra-high vacuum.

In one embodiment, the temperature of the raw material source is a temperature at which the partial pressure of the evaporated material reaches 10 ^-6 mbar in the ultra-high vacuum.

In an embodiment, the deposition temperature of the reduced material is 180-350°C, such as 200°C, 230°C, 250°C, 300°C, or 320°C.

In an embodiment, the deposition rate of the reduced material is 0.2 to 0.8 nm/min, for example, 0.3 nm/min, 0.35 nm/min, 0.4 nm/min, 0.45 nm/min, 0.5 nm/min, 0.55 nm /min, 0.6nm/min, 0.65nm/min or 0.7nm/min, etc.

In an embodiment, the deposition time of the reduced material is 20-60 min, such as 25 min, 30 min, 35 min, 40 min, or 50 min.

In one embodiment, the deposition of the reduced material is performed under vacuum conditions, and the vacuum degree is ≤ 10 ^-6 mbar, for example, 10 ^-7 mbar, 2×10 ^-7 mbar, 4×10 ^-7 mbar, 5×10 ^-7 mbar or 8×10 ^-7 mbar, etc.

In one embodiment, the metal element includes chromium.

The metal element used in this application is a metal with strong reducibility.

In one embodiment, the temperature of the source of the deposited metal is a temperature at which the partial pressure of the evaporated material reaches 10 ^-6 mbar in the ultra-high vacuum.

In one embodiment, the deposition temperature of the elemental metal is 180-350°C, such as 200°C, 230°C, 250°C, 300°C, or 320°C.

In an embodiment, the deposition rate of the elemental metal is 0.1-0.3 nm/min, such as 0.15 nm/min, 0.2 nm/min, 0.25 nm/min, or 0.3 nm/min.

In one embodiment, the deposition time of the elemental metal is 15-30 min, for example, 16 min, 18 min, 20 min, 22 min, 25 min, or 28 min.

In one embodiment, the deposition of the metal element is carried out under vacuum conditions, and the vacuum degree is ≤10 ^-6 mbar, such as 10 ^-7 mbar, 2×10 ^-7 mbar, 4×10 ^-7 mbar, 5×10 ^-7 mbar or 8×10 ^-7 mbar, etc.

In one embodiment, the growth method of the reduced material is epitaxial deposition, and the deposition of the reduced material is performed on a substrate.

In one embodiment, before the growth of the reduced material, the method further includes: heating the substrate to remove the oxide layer on the surface of the substrate, cooling to the growth temperature of the reduced material and keeping the temperature maintained.

In an embodiment, the temperature for removing the oxide layer on the surface of the substrate is 550-620°C, such as 560°C, 570°C, 580°C, 590°C, 600°C, or 610°C.

In an embodiment, the substrate includes sapphire.

As an exemplary technical solution, a method for preparing a heterojunction structure material described in this application, wherein:

Heating the substrate to remove the oxide layer on the surface of the substrate, cooling it to the growth temperature of the reduced material and keeping it warm includes: heating the sapphire substrate to 550-620°C, removing the oxide layer on the sapphire surface, and cooling down to the The growth temperature of the reducing material Bi ₂ Te ₃ is 230°C and the heat preservation is maintained;

Growing the reduced material by the growth method of epitaxial deposition includes: heating the Bi ₂ Te ₃ source to 460～500℃ under the condition of vacuum ≤10 ^-6 mbar, and depositing to the sapphire at a rate of 0.3～0.6nm/min Above, the deposition time is 20-30min;

Depositing elemental metal on the upper surface of the reduced material includes: heating a Cr source to 850-1150°C under the condition of a vacuum degree of ≤10 ^-6 mbar and then depositing it on the surface where Bi ₂ Te ₃ is deposited, and the deposition rate 0.1～0.3nm/min, deposition time is 15～30min;

Repeating the growth of the reduced material and the deposition of elemental metal on the upper surface of the reduced material n-1 times to obtain a heterojunction structure material includes: repeating the deposition process of Bi ₂ Te ₃ and Cr n-1 times , Get the heterojunction structure material.

This application provides a use of a heterojunction structure material, which is used in a new type of functional electronic device.

After reading and understanding the drawings and detailed description, other aspects can be understood.

Description of the drawings

Figure 1 is a schematic diagram of the preparation process of Example 1 of the present application;

2a and 2b are the reflection high-energy electron diffraction (Reflection High-Energy Electron Diffraction, RHEED) diagrams of the heterojunction structure material obtained in Example 1 of the present application, wherein FIG. 2a is the reduction material layer (Bi ₂ Te ₃ ) Reflective high-energy electron diffraction pattern, Figure 2b is a reflection-type high-energy electron diffraction pattern after depositing a metal compound layer (chromium telluride);

3 is an X-ray diffraction diagram of the heterojunction structure material obtained in Example 1 of the present application;

4a and 4b are transmission electron microscope topography diagrams of the heterojunction structure material obtained in Example 1 of the present application, wherein FIG. 4a is a cross-sectional topography diagram of the heterojunction structure material sample, and FIG. The topographic image obtained by zooming in the frame area.

Detailed ways

To facilitate the understanding of this application, the following examples are listed in this application. It should be understood by those skilled in the art that the described embodiments are only to help understand the application and should not be regarded as specific limitations to the application.

Example 1

A method for preparing a heterojunction structure material includes steps (1) to (4).

In step (1), the sapphire substrate is heated to 600°C, and then cooled to 230°C and kept warm.

In step (2), the Bi ₂ Te ₃ source is heated to 490°C under the condition of vacuum ≤ 10 ^-6 mbar, and then deposited on the sapphire at a rate of 0.5 nm/min. The deposition time is 24 min, as shown in the figure As shown in 1(a), Bi ₂ Te ₃ is deposited on sapphire (Al ₂ O ₃ ).

In step (3), under the condition of vacuum ≤10 ^-6 mbar, the Cr source is heated to 1110° C. and then deposited on the surface where Bi ₂ Te ₃ is deposited in step (1). The deposition rate is 0.2 nm/ min, the time is 20min; as shown in Fig. 1(b) and (c), Cr is deposited on the surface of Bi ₂ Te ₃ deposited in Fig. 1(a). After Cr reacts with Bi ₂ Te ₃ , the growth is finally formed Chromium telluride on the surface of Bi ₂ Te ₃ .

In step (4), the deposition process of Bi ₂ Te ₃ and Cr is continued a times, and the obtained heterojunction structure material with Bi ₂ Te ₃ thickness of 12 nm and chromium telluride thickness of 2 nm in each stack unit is obtained.

Figures 2a and 2b are reflection high-energy electron diffraction (RHEED) diagrams of the heterojunction structure material, wherein Figure 2a is the reflection high-energy electron diffraction diagram of the reduced material layer (Bi ₂ Te ₃ ), and Figure 2b is the deposition The reflection high-energy electron diffraction pattern after the metal compound layer (chromium telluride). According to the ratio of the spacing between fringe I (Bi ₂ Te ₃ ) and fringe II in the figure, the in-plane lattice constant of fringe II can be calculated as 3.98 angstroms , Indicating that the deposited metal compound layer is indeed chromium telluride, and the crystal quality is high, and the surface is flat.

Figure 3 is an X-ray diffraction pattern of the heterojunction structure material. It can be seen from the figure that in addition to the diffraction peaks of sapphire (SA) and Bi ₂ Te ₃ , chromium telluride is observed at a position of 29.8° Diffraction peaks confirm the presence of chromium telluride.

Figures 4a and 4b are the transmission electron microscope topography of the heterojunction structure material. From Figure 4a, you can see obvious light and dark stripes. The dark stripe area indicated by the arrow is the chromium telluride area, and the bright area corresponds to Is the Bi ₂ Te ₃ area. Enlarge the box in the figure to get Figure 4b. From the figure, 1 corresponds to the chromium telluride area, and 2 corresponds to the Bi ₂ Te ₃ area. It can be seen from the figure that the chromium telluride area and Bi ₂ A clear interface structure is formed between Te ₃ regions.

Example 2

The difference from Example 1 is that in step (3), the Cr source is replaced with a vanadium source, and the evaporation temperature of the vanadium source is adjusted to 1600° C. to obtain vanadium telluride grown on the surface of Bi ₂ Te ₃ .

Example 3

The difference from Example 1 is that the deposition time in step (3) is 15 minutes, and the thickness of chromium telluride in each stack unit obtained is 3 nm.

Example 4

In step (1), the sapphire substrate is heated to 550°C, and then cooled to 180°C and kept warm.

In step (2), the Mo source is heated to 1800°C and the ZnS source is heated to 850°C under the condition of vacuum ≤10 ^-6 mbar, and then deposited on the sapphire at a rate of 0.2nm/min to generate MoS ₂ , The deposition time is 60min.

In step (3), under the condition of vacuum ≤10 ^-6 mbar, the Cr source is heated to 1100° C. and then deposited on the surface where MoS ₂ is deposited in step (1). The deposition rate is 0.2 nm/min. The time is 20min.

In step (4), the deposition process of MoS ₂ and Cr is continued a times to obtain a heterojunction structure material.

Example 5

In step (1), the sapphire substrate is heated to 620°C, and then cooled to 350°C and kept warm.

In step (2), the ZnSe source is heated to 760°C under the condition of vacuum ≤10 ^-6 mbar, and then deposited on the sapphire at a rate of 0.8 nm/min, and the deposition time is 20 min.

In step (3), under the condition of vacuum ≤10 ^-6 mbar, the Cr source is heated to 1150°C and then deposited on the surface where ZnSe is deposited in step (1). The deposition rate is 0.2nm/min. For 20min.

In step (4), the deposition process of ZnSe and Cr is continued a times to obtain a heterojunction structure material.

Comparative example 1

In step (2), the Bi ₂ Te ₃ source is heated to 490° C. under the condition of vacuum ≤ 10 ^-6 mbar, and then deposited on the sapphire at a rate of 0.5 nm/min, and the deposition time is 24 min.

In step (3), after the sapphire substrate is heated to 260°C under the condition of vacuum ≤10 ^-6 mbar, the Cr source and Te source are heated to 1110°C and 350°C respectively, and then deposited to step (1) _On the surface where Bi ₂ Te ₃ is deposited, the deposition rate is 0.2 nm/min and the time is 20 min.

In step (4), the deposition process of Bi ₂ Te ₃ and Cr and Te is continued a times, and the heterojunction structure material cannot be obtained.

The prepared heterojunction structure material is subjected to the following performance tests.

Confirm whether the heterojunction interface is clear and flat: When a is 3, use a scanning transmission electron microscope to observe the interface flatness of the obtained heterojunction structure material. If you can see the clear and straight boundary between the two materials, it means that the heterojunction interface is clear and flat; if you can't see the clear and straight boundary between the two materials, it means the interface is not clear and uneven.

Confirm whether the reduced material is decomposed: When a is 3, if a clear heterojunction structure is not observed, it means that the reduced material has decomposed.

Confirm whether it is a superlattice structure: Observe the cross-sectional morphology of the sample through a scanning transmission electron microscope, if two or more materials appear alternately grow in thin layers of a few nanometers to tens of nanometers and maintain a strict period It means that a super-lattice structure is formed; if two or more materials do not grow alternately in thin layers of a few nanometers to tens of nanometers and maintain a strict periodic arrangement, no super-lattice structure is formed. Lattice structure.

Determine the maximum value of a: Repeat the deposition process of step (4) in Examples 1-5 and Comparative Example 1 a times, until the crystal quality of the material deteriorates so that a clear heterojunction interface cannot be formed, and calculate the a value.

Table 1

It can be seen from Table 1 that the heterojunction structure material obtained by the reduction growth method of the present application has good interface clarity, and compared with the method of Comparative Example 1, it can effectively prevent the decomposition of the reduced material, thereby forming a clear interface Heterojunction structure and even high-quality superlattice structure, and the decomposition of the reduced material in Comparative Example 1 caused the clarity and flatness of the heterojunction interface to decrease, and the superlattice could not be prepared.

In the heterojunction structure material described in the present application, a heterojunction is formed between the reduced material layer or intermediate product layer and the metal compound layer, and the heterojunction interface has high definition; at the same time, the reduced material layer or intermediate product is used The multilayer structure with alternating layers and metal compound layers can realize multiple functional interfaces or channels in a single material, which greatly improves product performance.

This application uses the strong reducibility of the elemental metal to reduce the metal element in the reduced material and react with the non-metal element to form a metal compound, thereby forming a heterojunction structure between the metal compound or intermediate product and the reduced material. The heterojunction has a clear interface structure and good performance. At the same time, the preparation method of the present application can prepare a multilayer structure, and can obtain a superlattice structure material; in the related art, metal elements and non-metal elements are used to enter the chamber together For the method of depositing and generating metal compounds, this application adopts the method of preparing metal compounds by reduction. The growth temperature of the metal compounds is lower, the reduced materials are not easily thermally decomposed, and the obtained heterojunction structure materials have better performance.

The preparation method of the present application is suitable for growing heterojunctions that are difficult to grow due to the different growth temperature windows of the materials forming the heterojunction. At the same time, the preparation method of the present application can prepare a multi-layer structure and further obtain a superlattice structure material. The heterojunction structure material is suitable for the field of new functional electronic devices.

Claims

A heterojunction structure material, the heterojunction structure material includes n layers of superimposed units, each of the superimposed units includes a reduced material layer and a metal compound layer attached to the reduced material layer, where n≥ 1.
The material of claim 1, wherein n≧2.
The material of claim 2, wherein n≥3.
The material according to claim 3, wherein n≥10.
The heterojunction structure material according to any one of claims 1 to 4, wherein the metal compound includes a chromium-based metal compound, and the chromium-based metal compound includes any one of chromium sulfide, chromium selenide, and chromium telluride Species or a combination of at least two;

In each of the overlapping units, the average thickness of the metal compound layer is 1.5-9 nm.
5. The heterojunction structure material according to any one of claims 1 to 5, wherein, in each of the superimposed units, the average thickness of the reduced material layer is 6-18 nm;

The reduced material includes any one or a combination of at least two of sulfide, selenide and telluride.
The heterojunction structure material according to claim 6, wherein the reduced material comprises any one or a combination of at least two of metal sulfide, metal selenide and metal telluride, and the metal sulfide, The reducibility of metal elements in metal selenide and metal telluride is weaker than that of chromium.
8. The heterojunction structure material of claim 7, wherein the reduced material comprises any one or a combination of at least two of bismuth telluride, molybdenum sulfide, and zinc selenide.
A method for preparing a heterojunction structure material according to any one of claims 1-8, which comprises:

Growth of reduced materials;

Depositing elemental metal on the upper surface of the reduced material;

Repeating the growth of the reduced material and the deposition of elemental metal on the upper surface of the reduced material n-1 times to obtain a heterojunction structure material.
9. The method of claim 9, wherein growing the reduced material comprises: growing the reduced material by epitaxial deposition or single crystal growth;

In the case where the growth mode of the reduced material is epitaxial deposition, the source temperature of the epitaxial deposition is the evaporation temperature or sublimation temperature of the reduced material; the deposition temperature of the reduced material is 180-350°C; The deposition rate of the reduced material is 0.2-0.8 nm/min; the deposition time of the reduced material is 20-60 min; the deposition of the reduced material is performed under vacuum conditions, and the vacuum degree is ≤ 10 -6 mbar.
The method according to claim 10, wherein the temperature of the raw material source is a temperature at which the partial pressure of the evaporated material reaches 10 -6 mbar in the ultra-high vacuum.
The method according to any one of claims 9-11, wherein the elemental metal includes chromium;

The raw material source temperature of the deposited metal element is a temperature at which the partial pressure of the vaporized material reaches 10 -6 mbar in an ultra-high vacuum; the deposition temperature of the metal element is 180-350° C.; the deposition rate of the metal element It is 0.1-0.3nm/min; the deposition time of the elemental metal is 15-30min; the deposition of the elemental metal is performed under vacuum conditions, and the vacuum degree is less than or equal to 10 -6 mbar.
The method according to any one of claims 9-12, wherein the growth mode of the reduced material is epitaxial deposition, and the deposition of the reduced material is performed on a substrate;

Before the growth of the reduced material, the method further includes: heating the substrate to remove the oxide layer on the surface of the substrate, and lowering the temperature to the growth temperature of the reduced material and keeping it warm;

Wherein, the temperature for removing the oxide layer on the surface of the substrate is 550-620°C; the substrate includes sapphire.
The method of claim 13, wherein:

Heating the substrate to remove the oxide layer on the surface of the substrate, cooling to the growth temperature of the reduced material and keeping it warm is: heating the sapphire substrate to 550-620°C, removing the oxide layer on the sapphire surface, and cooling it down The growth temperature of the reducing material Bi 2 Te 3 is 230°C and the heat preservation is maintained;

Growing the reduced material by the growth method of epitaxial deposition includes: heating the Bi 2 Te 3 source to 460～500℃ under the condition of vacuum ≤10 -6 mbar, and depositing to the material at a rate of 0.3～0.6nm/min On sapphire, the deposition time is 20-30min;

Depositing elemental metal on the upper surface of the reduced material includes: heating a Cr source to 850-1150°C under the condition of a vacuum degree of ≤10 -6 mbar and then depositing it on the surface where Bi 2 Te 3 is deposited, and the deposition rate 0.1～0.3nm/min, deposition time is 15～30min;

Repeating the growth of the reduced material and the deposition of elemental metal on the upper surface of the reduced material n-1 times to obtain a heterojunction structure material: repeating the deposition process of Bi 2 Te 3 and Cr n-1 times , Get the heterojunction structure material.
A use of the heterojunction structure material according to any one of claims 1-8, which is used in a new type of functional electronic device.