A method for ex-situ growth of topological superconducting heterojunctions

Abstract

The present invention relates to a method for non-in-situ growth of topological superconducting heterojunctions. In the present invention, argon ions in a molecular beam epitaxy chamber are used to etch a single-crystalline TiN thin film that has been exposed to air due to cross-device transfer. The argon ions are accelerated by an anode electric field and collide with the surface of the single-crystalline TiN thin film, thereby removing impurity atoms and dust on the surface of the single-crystalline TiN thin film, solving the problems of high cost increase and film surface contamination caused by cross-device in-situ growth. At the same time, compared with the high-temperature annealing technology, the etching method of the present invention can greatly reduce the growth time, avoid contaminating the ultra-high vacuum window, and avoid affecting the service life of the equipment. Then, on the surface of the adjacent single-crystalline TiN thin film under ultra-high vacuum, a single-crystalline Bi2Se3 thin film is epitaxially grown on the single-crystalline TiN thin film to obtain a TiN / Bi2Se3 topological superconducting heterojunction.

Description

Technical Field

[0001] The present invention relates to the technical field of topological superconducting heterojunctions, and in particular to a method for non-in-situ growth of topological superconducting heterojunctions. Background Art

[0002] Topological superconducting heterojunctions have great application potential in future topological quantum computing, and can provide effective solutions for people in the fields of cryptographic analysis, weather forecasting, drug design, etc. However, the construction of practical topological superconducting heterojunctions still faces multiple challenges. Since the chemical properties of superconducting layer materials are generally active and very sensitive to surface contamination or oxidation, which can easily cause the degradation of the topological-superconducting interface, topological superconducting heterojunctions are usually grown on the surface of in-situ cleaved superconductor bulk single crystals, or on the surface of in-situ grown superconducting thin films to avoid interface degradation. At present, the preparation of topological superconducting heterojunctions is mostly based on in-situ preparation in the same cavity or vacuum interconnection system. The in-situ preparation process not only greatly increases the threshold for preparing topological superconducting heterojunctions, but is also incompatible with device manufacturing processes such as lithography, which brings obstacles to the practical development of topological quantum devices. The vacuum interconnection system will further increase the high cost of equipment construction and maintenance on the high cost of the original equipment, and will increase the complexity and instability of the equipment system. Therefore, realizing a simple, feasible, ex-situ prepared topological superconducting heterojunction with a highly matched structure is of great significance for the preparation of practical topological quantum devices, and ex-situ, cross-device growth has significant cost advantages.

[0003] The non-in-situ growth of topological superconducting heterojunctions in the prior art is carried out by high temperature annealing. However, the technical method of high temperature annealing has the following defects:

[0004] (1) High temperature annealing takes a long time, usually more than ten hours, which affects efficiency;

[0005] (2) High temperature annealing operations cannot remove the oxide layer formed when single crystal TiN films or other materials are exposed to air;

[0006] (3) Long-term annealing will damage the life of the heating module, and the heating module is expensive, which increases the growth cost of the topological superconducting heterojunction;

[0007] (4) Long-term high-temperature annealing will cause contamination of the ultra-high vacuum window. The ultra-high vacuum window is a window for checking the growth status and sample status. In order to clean this window, many vacuum pumps must be stopped. After cleaning the ultra-high vacuum window, it takes about 3-7 days to pump the vacuum back to the original level. The whole process wastes a lot of time. Summary of the invention

[0008] The technical problem to be solved by the present invention is how to solve the problem of increased cost of in-situ growth and surface contamination of thin films caused by cross-equipment. In order to overcome the above defects of the prior art, the present invention provides a method for non-in-situ growth of topological superconducting heterojunctions.

[0009] The present invention provides a method for non-in-situ growth of a topological superconducting heterojunction, comprising:

[0010] Step 1. Al 2 O 3 As substrate, in Al 2 O 3 Growing a single crystal TiN thin film on a substrate;

[0011] Step 2. Al2O3 with single crystal TiN film grown on it 2 O 3 The substrate is transferred into a molecular beam epitaxy chamber, and then the single crystal TiN film exposed to air is subjected to argon ion etching by using an argon ion etching technique in the molecular beam epitaxy chamber, so as to remove an oxide layer generated on the single crystal TiN film during exposure to air during the transfer process, as well as impurities and dust adsorbed on the surface of the single crystal TiN film;

[0012] Step 3: Using molecular beam epitaxy technology, single crystal Bi is epitaxially grown on the single crystal TiN film in an ultra-vacuum state in the molecular beam epitaxy chamber. 2 Se 3 Thin film, thus obtaining TiN / Bi 2 Se 3 Topological superconducting heterojunctions.

[0013] Compared with the prior art, the present application has the following advantages: the present invention utilizes argon ions in a molecular beam epitaxy chamber to perform argon ion etching on a single crystal TiN film that has been exposed to air due to cross-device. The argon ions are accelerated by the anode electric field and collide with the surface of the single crystal TiN film, thereby removing impurity atoms and dust on the surface of the single crystal TiN film, solving the problem of high cost and film surface contamination caused by cross-device in-situ growth. At the same time, compared with high-temperature annealing technology, the etching method of the present invention can greatly reduce the growth time, avoid contaminating the ultra-vacuum window, and avoid affecting the service life of the equipment. Then, a single crystal Bi is epitaxially grown on the single crystal TiN film under ultra-vacuum on the surface of the single crystal TiN film. 2 Se 3 Thin film, TiN / Bi 2 Se 3 Topological superconducting heterojunctions.

[0014] In a possible implementation manner, the argon ion etching of the single crystal TiN film in the molecular beam epitaxy chamber in step 2 specifically includes:

[0015] Step 201: Inject argon ion gas into the molecular beam epitaxy chamber to make the vacuum degree in the molecular beam epitaxy chamber at 10 -6 mbar;

[0016] Step 202: Use an argon ion gun to perform argon ion etching on the single crystal TiN film.

[0017] In a possible implementation manner, the argon ion etching of the single crystal TiN film in step 202 sequentially includes rough etching and fine etching, specifically including:

[0018] Step 202A. Measure the single crystal quality of the single crystal TiN film using a low energy electron diffraction measuring instrument;

[0019] Step 202B. Roughly etch the single crystal TiN film using an argon ion gun;

[0020] Step 202C. Fine etching the single crystal TiN film using an argon ion gun;

[0021] Step 202D. Use a low energy electron diffraction measuring instrument to measure the single crystal quality of the single crystal TiN film after fine etching; and compare the low energy electron diffraction images before and after argon ion etching to determine whether the impurities and dust adsorbed on the surface of the single crystal TiN film are removed by argon ion etching.

[0022] Compared with single etching, the technical solution of rough etching first and then fine etching can improve the flatness of the surface of single-crystal TiN film and improve the epitaxial growth of single-crystal Bi 2 Se 3 The quality of the film.

[0023] In a possible implementation manner, in step 3, a single crystal Bi is epitaxially grown on the single crystal TiN film. 2 Se 3 The film includes a first growth stage and a second growth stage, wherein:

[0024] The first growth stage specifically includes:

[0025] Step 301A. Adjust Al 2 O 3 The substrate current is 1.4A, and the Al 2 O 3 The substrate is heated to the operating temperature;

[0026] Step 302A. Turn on the Se evaporation source, the temperature of the Se evaporation source is 140°C, and stabilize for a third preset time;

[0027] Step 303A. When the vacuum degree in the molecular beam epitaxy chamber rises to 3×10 -9 ~4×10-9 mbar level, turn on the Bi evaporation source, the temperature of the Bi evaporation source is 450℃, and start the single crystal Bi 2 Se 3 The first stage of film growth; after the first preset growth time, the Bi evaporation source is turned off; the first growth stage ends;

[0028] The second growth stage specifically includes:

[0029] Step 301B. Adjust Al 2 O 3 The substrate current is set to 2.3~2.6A. When the infrared test temperature is stabilized at 240~260℃, the Bi evaporation source is turned on. After the second preset growth time, the single crystal Bi 2 Se 3 After the film is grown on the single crystal TiN film, turn off the Bi evaporation source and the Se evaporation source; reduce the Al 2 O 3 The current of the substrate is turned off after reaching 0 A, and the second growth stage ends.

[0030] Further, based on the argon ion etching of the single crystal TiN film in the molecular beam epitaxial chamber in step 2, the growth environment in the molecular beam epitaxial chamber is placed in a Se-rich environment for a first preset time to grow the single crystal Bi 2 Se 3 Thin film growth is beneficial to the single crystal Bi grown in the first growth stage 2 Se 3 The lattice parameters of the film are close to those of single-crystal TiN film, and then the Al 2 O 3 The temperature of the substrate is then used to grow single crystal Bi in a Se-rich molecular beam epitaxy chamber. 2 Se 3 Thin film, improve single crystal Bi 2 Se 3 The quality of film growth.

[0031] In a possible implementation, the Bi in the Bi evaporation source is bismuth particles with a purity of 99.997%, and the Se in the Se evaporation source is selenium pellets with a purity of 99.999%. High-purity Bi evaporation sources and Se evaporation sources are used to avoid impurities affecting the single crystal Bi 2 Se 3 Thin film growth.

[0032] In a possible implementation manner, the operating temperature of step 301A is 56-62° C., to prevent Se from being deposited on Al 2 O 3 On substrate.

[0033] In a possible implementation manner, the first preset duration of step 303A is 2 minutes; and the second preset duration of step 301B is 28 minutes.

[0034] In a possible implementation manner, the Al 2 O 3 The crystal plane orientation of the substrate is (0001), the thickness of the single crystal TiN film is 70 nm, and the crystal plane orientation of TiN is (111). BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a low energy electron diffraction image of the single crystal TiN film before etching of the present invention;

[0036] Figure 2 It is a low energy electron diffraction image of the single crystal TiN film after etching of the present invention;

[0037] Figure 3 is an atomic force microscope image of a single crystal TiN film before etching of the present invention;

[0038] Figure 4 is an atomic force microscope image of the single crystal TiN film after etching of the present invention;

[0039] Figure 5 The present invention Bi 2 Se 3 / TiN / Al 2 O 3 Full X-ray diffraction spectrum of

[0040] Figure 6 The single crystal Bi 2 Se 3 Half-maximum width image of the single-crystalline quality of the thin film. DETAILED DESCRIPTION

[0041] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0042] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0043] In the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0044] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] This specific embodiment specifically discloses a method for non-in-situ growth of a topological superconducting heterojunction, and the present invention is specifically applied to epitaxial growth of a single crystal Bi on a single crystal TiN film. 2 Se 3 Thin film, thus obtaining TiN / Bi 2 Se 3 A topological superconducting heterojunction, wherein the method for ex-situ growing a topological superconducting heterojunction comprises:

[0046] Step 1. Al 2 O 3 As substrate, magnetron sputtering technology was used to deposit Al 2 O 3 A single crystal TiN film is grown on the substrate; an Al substrate on which the single crystal TiN film is grown is taken out from the magnetron sputtering chamber; 2 O 3 substrate;

[0047] Step 2. Al2O3 with single crystal TiN film grown on it 2 O 3 The substrate is transferred to the molecular beam epitaxy chamber. During the cross-device transfer process, the single-crystal TiN film is exposed to the air and absorbs impurities and dust. Therefore, it is necessary to use argon ion etching technology in the molecular beam epitaxy chamber to perform argon ion etching on the single-crystal TiN film exposed to the air to remove the impurities and dust absorbed on the surface of the single-crystal TiN film due to exposure to the air; specifically, the following steps are included:

[0048] Step 201: Inject argon ion gas into the molecular beam epitaxy chamber to make the vacuum degree in the molecular beam epitaxy chamber at 10 -6 mbar;

[0049] Step 202: Turn on the argon ion gun, adjust the voltage of the argon ion gun, and perform argon ion etching on the single-crystalline TiN film; the argon ion etching of the single-crystalline TiN film includes rough etching and fine etching, specifically including:

[0050] Step 202A. Measure the single crystal quality of the single crystal TiN film using a low energy electron diffraction measuring instrument;

[0051] Step 202B. Turn on the argon ion gun, adjust the voltage of the argon ion gun to 3 kV, perform rough etching on the single crystal TiN film for 3 hours, and turn off the argon ion gun;

[0052] Step 202C. Turn on the argon ion gun, adjust the voltage of the argon ion gun to 1 kV, perform fine etching on the single crystal TiN film, the fine etching time is 3 h, and turn off the argon ion gun;

[0053] Step 202D. Using a low energy electron diffraction measuring instrument to measure the single crystal quality of the single crystal TiN film after fine etching; and by comparing the single crystal quality before and after argon ion etching to determine whether the impurities and dust adsorbed on the surface of the single crystal TiN film are removed by argon ion etching;

[0054] In the actual operation process of this specific embodiment, in step 1, two Al 2 O 3 A single crystal TiN film is grown on a substrate, wherein one single crystal TiN film is used as an experimental group and the other single crystal TiN film is used as a control group. After the single crystal TiN film of the control group undergoes step 1, an atomic force microscope is first used to test the roughness of the single crystal TiN film. After the single crystal TiN films of the experimental group and the control group undergo steps 1 and 2, the single crystal TiN film of the control group is taken out of the molecular beam epitaxy chamber and an atomic force microscope is used to test the roughness of the single crystal TiN film after etching.

[0055] By measuring the single crystal quality of the single crystal TiN film before and after etching using low energy electron diffraction from the control group, it is determined whether the impurities and dust on the single crystal TiN film due to exposure to air across the equipment are removed by argon ion etching technology; Figure 1 , Figure 2 As shown in the figure, it can be seen from the low-energy electron diffraction image that the single-crystalline TiN film has six clear spots before and after argon ion etching, proving that the single-crystalline TiN film has good crystal quality. The low-energy electron diffraction image of TiN after etching is brighter and clearer than that before etching, proving that argon ion etching removes impurities adsorbed by the single-crystalline TiN film due to exposure to air.

[0056] The roughness of the single crystal TiN film before and after etching was tested by atomic force microscopy from the control group to make the surface of the single crystal TiN film smoother. Figure 3 , Figure 4As shown, it can be seen from the atomic force microscopy image that the roughness of the single-crystalline TiN film changes from 0.514 nm to 0.301 nm before and after argon ion etching, proving that argon ion etching makes the single-crystalline TiN film smoother from coarse etching to fine etching.

[0057] Then, the single crystal TiN film of the experimental group was moved to the Bi 2 Se 3 Growth position, go to step 3.

[0058] Step 3: Using molecular beam epitaxy technology, single crystal Bi is epitaxially grown on the single crystal TiN film in an ultra-vacuum state in the molecular beam epitaxy chamber. 2 Se 3 Thin film, thus obtaining TiN / Bi 2 Se 3 A topological superconducting heterojunction; comprising a first growth stage and a second growth stage, wherein the first growth stage specifically comprises:

[0059] Step 301A. Adjust Al 2 O 3 The substrate current is 1.4A, and the Al 2 O 3 The substrate is heated to 56-62°C, preferably 56°C in this embodiment, and the Al 2 O 3 The substrate is heated to 56°C to make the molecular beam epitaxy chamber in step 302A in a Se-rich environment while preventing Se from being deposited on the Al 2 O 3 On the substrate;

[0060] Step 302A. Turn on the Se evaporation source, the temperature of the Se evaporation source is 140°C, and after stabilizing for a third preset time, the molecular beam epitaxy chamber is in a Se-rich environment;

[0061] Step 303A. When the vacuum degree in the molecular beam epitaxy chamber rises to 3×10 -9 ~4×10 -9 When the temperature reaches 450℃, turn on the Bi evaporation source and keep it stable for 5-10 minutes to ensure that the Bi particles are heated evenly. 2 Se 3 The first stage of film growth; after 2 minutes of growth, the Bi evaporation source is turned off; the first growth stage ends; at this time, the Se evaporation source is continuously turned on and kept at 140°C to avoid a continuous Se-rich atmosphere in the molecular beam epitaxy chamber;

[0062] The second growth stage specifically includes:

[0063] Step 301B. Adjust Al 2 O 3 The current of the substrate is increased to 2.3~2.6A. When the infrared test temperature is stabilized at 250℃, the Bi evaporation source is turned on. After 28 minutes of growth, the single crystal Bi 2 Se 3 After the film is grown on the single crystal TiN film, turn off the Bi evaporation source and the Se evaporation source; reduce the Al 2 O 3 The current of the substrate is turned off after reaching 0 A, and at the same time, the temperature of the Bi heating source and the temperature of the Se heating source are slowly reduced, and the second growth stage ends.

[0064] The single crystal TiN film used in the present invention is a superconductor, and the single crystal Bi epitaxially grown on the single crystal TiN film 2 Se 3 The film is a topological insulator, and the single crystal TiN film and single crystal Bi 2 Se 3 The topological superconducting heterojunction will be formed in the thin film. Therefore, the present invention adopts the 2 O 3 First, a single crystal TiN film is grown on the substrate, and then, in a Se-rich environment, a single crystal Bi is grown in the first growth stage. 2 Se 3 Thin film, making single crystal Bi 2 Se 3 The lattice parameters of the film are close to those of the single-crystalline TiN film under the atomic force of the single-crystalline TiN film. Then, in the Se-rich environment, the single-crystalline Bi 2 Se 3 The lattice parameters of the thin film approach those of single crystal Bi due to its own interatomic forces. 2 Se 3 The lattice parameters of the film itself.

[0065] Will get Bi 2 Se 3 / TiN topological superconducting heterojunction samples were taken out and further tested by X-ray diffraction and half-peak width, such as Figure 5 As shown in the full X-ray diffraction spectrum, it can be seen that single crystal Bi was successfully epitaxially grown on the single crystal TiN film. 2 Se 3 film.

[0066] like Figure 6 As shown, the Bi measured by X-ray diffraction 2 Se 3 The half-peak width is 0.15°, indicating that the epitaxial Bi on TiN 2 Se 3With excellent crystal quality.

[0067] The present invention utilizes argon ions in a molecular beam epitaxy chamber to perform argon ion etching on a single crystal TiN film that has been exposed to air due to cross-device. The argon ions are accelerated by an anode electric field and collide with the surface of the single crystal TiN film, thereby removing impurity atoms and dust on the surface of the single crystal TiN film, solving the problem of high cost and film surface contamination caused by cross-device in-situ growth. Then, a single crystal Bi is epitaxially grown on the single crystal TiN film under ultra-vacuum on the surface of the single crystal TiN film. 2 Se 3 Thin film, TiN / Bi 2 Se 3 Topological superconducting heterojunctions.

[0068] In this specific embodiment, the Bi in the Bi evaporation source is bismuth particles with a purity of 99.997%, and the Se in the Se evaporation source is selenium pellets with a purity of 99.999%. High-purity Bi evaporation sources and Se evaporation sources are used to avoid impurities affecting the single crystal Bi 2 Se 3 Thin film growth.

[0069] Furthermore, the Al 2 O 3 The crystal plane orientation of the substrate is (0001), the thickness of the single crystal TiN film is 70 nm, and the crystal plane orientation of TiN is (111). 2 O 3 The lattice of the single crystal TiN film grown on the substrate is the same as that of Al 2 O 3 The substrate has a consistent hexagonal lattice, which improves the growth quality of the single crystal TiN film.

[0070] Compared with the technical solution of non-in-situ growth by high-temperature annealing, the present invention adopts the technical solution of argon ion etching of the single crystal TiN film that has been exposed to air due to cross-device. On the one hand, the present invention solves the problem that cross-device in-situ growth requires high costs and causes film surface contamination, and reduces the growth time. For example, the high-temperature annealing method requires more than ten hours, while the etching technology of the present invention only requires six hours at most, which greatly saves the growth time; on the other hand, the use of argon ion etching can avoid contaminating the ultra-vacuum window, and will not cause the loss of the heating module and affect the life of the heating module; in addition, in the subsequent single crystal TiN film growth process, the first growth stage of single crystal Bi is carried out on the etched single crystal TiN film. 2 Se 3 The lattice parameters of the film are close to those of the single crystal TiN film under the atomic force of the single crystal TiN film; then the single crystal Bi2 Se 3 Thin film growth, improving single crystal Bi 2 Se 3 The quality of film growth.

[0071] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description, and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0072] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0073] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for ex-situ growth of a topological superconducting heterojunction, characterized in that: include: Step 1. Using Al2O3 as a substrate, growing a single crystal TiN film on the Al2O3 substrate; the thickness of the single crystal TiN film is 70nm; Step 2. Transferring the Al2O3 substrate on which the single crystal TiN film is grown into a molecular beam epitaxy chamber, and then performing argon ion etching on the single crystal TiN film using an argon ion etching technique in the molecular beam epitaxy chamber to remove an oxide layer generated on the single crystal TiN film during exposure to air during the transfer process, as well as impurities and dust adsorbed on the surface of the single crystal TiN film; specifically comprising: Step 201: Inject argon ion gas into the molecular beam epitaxy chamber to make the vacuum degree in the molecular beam epitaxy chamber at 10 -6 mbar; Step 202: using an argon ion gun to perform argon ion etching on the single-crystalline TiN film, wherein the roughness of the single-crystalline TiN film before argon ion etching is 0.514 nm; performing argon ion etching on the single-crystalline TiN film includes rough etching and fine etching in sequence, specifically including: Step 202A. Measure the single crystal quality of the single crystal TiN film using a low energy electron diffraction measuring instrument; Step 202B. using an argon ion gun to perform rough etching on the single crystal TiN film; including turning on the argon ion gun, adjusting the voltage of the argon ion gun to 3 kV, performing rough etching on the single crystal TiN film for a rough etching time of 3 hours, and turning off the argon ion gun; Step 202C. Use an argon ion gun to perform fine etching on the single crystal TiN film; turn on the argon ion gun, adjust the voltage of the argon ion gun to 1 kV, perform fine etching on the single crystal TiN film, the fine etching time is 3 hours, and turn off the argon ion gun; Step 202D. Using a low energy electron diffraction instrument to measure the single crystal mass of the single crystal TiN film after fine etching; and by comparing the single crystal mass before and after argon ion etching to determine whether the impurities and dust adsorbed on the surface of the single crystal TiN film are removed by argon ion etching; the roughness of the single crystal TiN film after argon ion etching is 0.301nm; Step 3. Using molecular beam epitaxy technology, in an ultra-vacuum state in a molecular beam epitaxy chamber, epitaxially grow a single crystal Bi2Se3 film on the single crystal TiN film, thereby obtaining a TiN / Bi2Se3 topological superconducting heterojunction.

2. The method for ex-situ growth of a topological superconducting heterojunction according to claim 1, characterized in that: In the step 3, a molecular beam epitaxy technique is used to epitaxially grow a single crystal Bi2Se3 film on a single crystal TiN film under an ultra-vacuum state in a molecular beam epitaxy chamber, including a first growth stage and a second growth stage, specifically including: First growth stage Step 301A. Adjust the current of the Al2O3 substrate to 1.4A, and heat the Al2O3 substrate to a first temperature; Step 302A. Turn on the Se evaporation source, the temperature of the Se evaporation source is 140°C; Step 303A. When the vacuum degree in the molecular beam epitaxy chamber rises to 3×10 -9 ~4×10 -9 When the temperature reaches the mbar level, the Bi evaporation source is turned on, the temperature of the Bi evaporation source is 450°C, and the first stage growth of the single crystal Bi2Se3 film begins; after the first preset growth time, the Bi evaporation source is turned off; the first growth stage ends; Second growth stage Step 301B. Adjust the current of the Al2O3 substrate to 2.3~2.6A. After the infrared test temperature stabilizes at 240~260℃, turn on the Bi evaporation source. After growing for the second preset time, the single crystal Bi2Se3 film is grown on the single crystal TiN film. Turn off the Bi evaporation source and the Se evaporation source. Reduce the current of the Al2O3 substrate to 0A at a uniform speed and then turn it off. The second growth stage ends.

3. The method for ex-situ growth of a topological superconducting heterojunction according to claim 2, characterized in that: The Bi in the Bi evaporation source is bismuth particles with a purity of 99.997%, and the Se in the Se evaporation source is selenium pills with a purity of 99.999%.

4. The method for ex-situ growth of a topological superconducting heterojunction according to claim 2, characterized in that: The working temperature of step 301A is 56-62°C.

5. The method for ex-situ growth of a topological superconducting heterojunction according to claim 2, characterized in that: The first preset duration of step 303A is 2 minutes; the second preset duration of step 301B is 28 minutes.

6. The method for ex-situ growth of a topological superconducting heterojunction according to claim 1, characterized in that: The crystal plane orientation of the Al2O3 substrate is (0001), and the crystal plane orientation of TiN is (111).

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