Electronic devices and methods for manufacturing electronic devices

Abstract

An electronic device (10) comprises: a superconducting electrode (20) containing PdTe2 or PdTe; and a TMD film (30) which contains a transition-metal dichalcogenide and which is layered on the superconducting electrode.

Description

Technical Field

[0001] The disclosed technology relates to an electronic device and a method for manufacturing an electronic device.

Background Art

[0002] As an electronic device including a transition metal dichalcogenide, the following are known. For example, a photoelectric device including a light receiving part including a transition metal dichalcogenide layer and a charge induction layer, a charge induction layer covering the transition metal dichalcogenide layer, and a detection part including a topological insulator layer disposed apart from the transition metal dichalcogenide layer is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In quantum computing, for example, while research on algorithms useful in the fields of quantum chemistry calculations, machine learning, and financial engineering is progressing, research on hardware including the transmon method is still in development. With the current small number of physical qubits and high error rate, not even a single useful logical qubit can be prepared.

[0005] Meanwhile, in the field of physics, the existence of special elementary particles called Majorana particles had been predicted. The transformation factor of these particles is a 2x2 unitary matrix, and the swapping of the physical positions of the particles itself constitutes a unitary transformation, i.e., a quantum operation. Quantum computers using Majorana particles utilize the fact that the sign change of the wave function when Majorana particles are swapped is the same as a quantum gate operation. While conventional quantum computers were rather analog in nature, qubits using Majorana particles can be said to be digital because they retain information through the relative positions of the particles, and swapping particle positions corresponds to a quantum gate operation. Because Majorana particles originate from the geometric properties of matter, they have high resistance to noise without compromising topology (geometric features).

[0006] A challenge with quantum computers using Majorana particles is that not a single qubit has yet been realized. Topological superconductors, which are low-dimensional structures of special superconductors, are attracting attention as materials in which Majorana particles may exist. However, suitable candidate materials for topological superconductors have not yet been discovered. Therefore, research is being conducted on the idea of ​​inducing superconductivity in a topological insulator by bringing a superconductor into contact with it and using the proximity effect.

[0007] A major problem in the development of Majorana qubits using topological insulators and superconductors is the stability of the topological insulator. Topological insulators such as WTe2, a type of transition metal dichalcogenite, have the disadvantage of being easily oxidized. Superconductors are also often easily oxidized. For example, Al and Nb, known as superconductors, form a passive oxide film on their surface. The presence of an oxide film at the interface between the topological insulator and the superconductor not only weakens the proximity effect but also slows the superconducting gap, negatively affecting the emergence of Majorana particles. In other words, the presence of an oxide film at the interface between the topological insulator and the superconductor creates energy levels within the superconducting gap, weakening the protection of Majorana particles by the topological properties of the material, and consequently shortening the lifetime of the Majorana particles. The above problem is faced not only in Majorana qubits but also in many electronic devices using transition metal dichalcogenite.

[0008] The disclosed technology aims to suppress the formation of oxide films at the interface between transition metal dichalcogenite and superconductors. [Means for solving the problem]

[0009] The electronic device relating to the disclosed technology comprises a superconducting electrode containing PdTe2 or PdTe, and a TMD film containing transition metal dichalcogenite laminated on the superconducting electrode. [Effects of the Invention]

[0010] According to the disclosed technology, the formation of oxide films at the interface between transition metal dichalcogenite and superconductors can be suppressed. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing an example of the configuration of an electronic device according to an embodiment of the disclosed technology. [Figure 2A] This is a cross-sectional view showing an example of a method for manufacturing an electronic device according to an embodiment of the disclosed technology. [Figure 2B]This is a cross-sectional view showing an example of a method for manufacturing an electronic device according to an embodiment of the disclosed technology. [Figure 2C] This is a cross-sectional view showing an example of a method for manufacturing an electronic device according to an embodiment of the disclosed technology. [Figure 2D] This is a cross-sectional view showing an example of a method for manufacturing an electronic device according to an embodiment of the disclosed technology. [Figure 2E] This is a cross-sectional view showing an example of a method for manufacturing an electronic device according to an embodiment of the disclosed technology. [Figure 2F] This is a cross-sectional view showing an example of a method for manufacturing an electronic device according to an embodiment of the disclosed technology. [Figure 2G] This is a cross-sectional view showing an example of a method for manufacturing an electronic device according to an embodiment of the disclosed technology. [Figure 2H] This is a cross-sectional view showing an example of a method for manufacturing an electronic device according to an embodiment of the disclosed technology. [Figure 3A] This figure shows an example of a method for obtaining a flake of a WTe2 single crystal according to an embodiment of the disclosed technology. [Figure 3B] This figure shows an example of a method for obtaining a flake of a WTe2 single crystal according to an embodiment of the disclosed technology. [Figure 3C] This figure shows an example of a method for obtaining a flake of a WTe2 single crystal according to an embodiment of the disclosed technology. [Figure 3D] This figure shows an example of a method for obtaining a flake of a WTe2 single crystal according to an embodiment of the disclosed technology. [Figure 3E] This figure shows an example of a method for obtaining a flake of a WTe2 single crystal according to an embodiment of the disclosed technology. [Figure 4] This figure shows how a superconductor is formed near the interface between the Pd and WDe2 films. [Figure 5A] This is a cross-sectional view showing an example of a method for manufacturing an electronic device using the MBE method or PLD method according to an embodiment of the disclosed technology. [Figure 5B] This is a cross-sectional view showing an example of a method for manufacturing an electronic device using the MBE method or PLD method according to an embodiment of the disclosed technology. [Figure 5C]It is a cross-sectional view showing an example of a method for manufacturing an electronic device using the MBE method or the PLD method according to an embodiment of the disclosed technology. [Figure 6] It is a cross-sectional view showing an example of the configuration of an electronic device according to another embodiment of the disclosed technology. [Figure 7A] It is a cross-sectional view showing an example of a method for manufacturing an electronic device according to another embodiment of the disclosed technology. [Figure 7B] It is a cross-sectional view showing an example of a method for manufacturing an electronic device according to another embodiment of the disclosed technology. [Figure 7C] It is a cross-sectional view showing an example of a method for manufacturing an electronic device according to another embodiment of the disclosed technology. [Figure 7D] It is a cross-sectional view showing an example of a method for manufacturing an electronic device according to another embodiment of the disclosed technology. [Figure 7E] It is a cross-sectional view showing an example of a method for manufacturing an electronic device according to another embodiment of the disclosed technology. [Figure 7F] It is a cross-sectional view showing an example of a method for manufacturing an electronic device according to another embodiment of the disclosed technology. [Figure 8A] It is a cross-sectional view showing an example of a method for partially thinning a WTe2 film by etching using the ALE method according to another embodiment of the disclosed technology. [Figure 8B] It is a cross-sectional view showing an example of a method for partially thinning a WTe2 film by etching using the ALE method according to another embodiment of the disclosed technology. [Figure 8C] It is a cross-sectional view showing an example of a method for partially thinning a WTe2 film by etching using the ALE method according to another embodiment of the disclosed technology. [Figure 8D] It is a cross-sectional view showing an example of a method for partially thinning a WTe2 film by etching using the ALE method according to another embodiment of the disclosed technology. [Figure 9A] It is a cross-sectional view showing an example of a manufacturing method when forming a superconducting electrode using a Pd·Te alternating laminated film. [Figure 9B] It is a cross-sectional view showing an example of a manufacturing method when forming a superconducting electrode using a Pd·Te alternating laminated film. [Figure 9C] A cross-sectional view showing an example of a manufacturing method when forming a superconducting electrode using a Pd·Te alternating multilayer film. [Figure 9D] A cross-sectional view showing an example of a manufacturing method when forming a superconducting electrode using a Pd·Te alternating multilayer film. [Figure 10] This is a plan view showing an example of the configuration of an electronic device according to another embodiment of the disclosed technology. [Figure 11] This is a plan view showing an example of the configuration of an electronic device according to another embodiment of the disclosed technology. [Modes for carrying out the invention]

[0012] Hereinafter, an example of an embodiment of the disclosed technology will be described with reference to the drawings. In each drawing, identical or equivalent components and parts will be given the same reference numerals, and redundant descriptions will be omitted. [First Embodiment] Figure 1 is a cross-sectional view showing an example of the configuration of an electronic device 10 according to a first embodiment of the disclosed technology. The electronic device 10 has a superconducting electrode 20 containing PdTe2 or PdTe, and a TMD film 30 (Transition Metal Dichalcogenide) containing transition metal dichalcogenite laminated on the superconducting electrode 20. The electronic device 10 is provided on a substrate 15. This is also possible. The material of the substrate 15 is not particularly limited, but for example, SiO2 can be used.

[0013] The transition metal dichalcogenite constituting the TMD film 30 may be a topological insulator. A topological insulator is a material that is an insulator in its interior and has metallic properties, exhibiting conductivity on its surface. The topological insulator may be, for example, WTe2. As the transition metal dichalcogenite constituting the TMD film 30, for example, WSe2, WS2, MoSe2, or MoS2 can be used. The TMD film 30 may be composed of a single-layer or multi-layer atomic layer material. The electronic device 10 is a bottom-contact type device in which the TMD film 30 covers the superconducting electrode 20.

[0014] The manufacturing method of the electronic device 10 will be described below. Figures 2A to 2H are cross-sectional views showing an example of the manufacturing method of the electronic device 10.

[0015] First, a resist mask 40 having openings 41 corresponding to the pattern of the superconducting electrode 20 is formed on the substrate 15 (Figure 2A). Next, a Pd·Te alternating multilayer film 23 is formed by alternately depositing a Pd film 21 and a Te film 22 on the substrate 15 via the resist mask 40 (Figure 2B). The Pd·Te alternating multilayer film 23 can be formed, for example, by alternately depositing Pd and Te with a thickness of several nanometers (maximum of about 10 nm) using a binary vapor deposition machine. It is also possible to form the Pd·Te alternating multilayer film 23 by co-deposition of Pd and Te. Furthermore, it is also possible to form the Pd·Te alternating multilayer film 23 by deposition or sputtering using a mixed target sintered with Pd and Te. To minimize surface oxidation, it is preferable that the uppermost layer of the Pd·Te alternating multilayer film 23 is a Pd film 21. This suppresses oxidation of the Pd·Te alternating multilayer film 23. After the Pd·Te alternating laminated film 23 is formed, it is also possible to expose the Pd·Te alternating laminated film 23 to the atmosphere or to contact it with an organic solvent or organic alkaline developer.

[0016] Next, the excess Pd·Te alternating multilayer film 23 deposited on the resist mask 40 is removed along with the resist mask 40. That is, the Pd·Te alternating multilayer film 23 is patterned by lift-off (Figure 2C).

[0017] Next, a TMD film 30 is formed on a substrate 16 that is different from the substrate 15 on which the Pd·Te alternating laminated film 23 is formed (Figure 2D). In the following description, the case in which the TMD film 30 is a WTe2 film 30A will be explained as an example, but the method described below is also applicable when the TMD film 30 is composed of a transition metal dichalcogenite other than WTe2.

[0018] For example, a WTe2 film 30A of one atomic layer or several atomic layers can be formed on the substrate 16 by transferring a detached piece of WTe2 single crystal onto the substrate 16. Figures 3A to 3E show an example of a method for obtaining a detached piece of WTe2 single crystal. The WTe2 single crystal is obtained by heating WO3 (tungsten oxide) and powdered Te in a quartz glass crucible. The thickness of the WTe2 single crystal is about 1 to 2 μm. The obtained WTe2 single crystal 30B is attached to the end of the adhesive surface of the adhesive tape 300 (Figure 3A).

[0019] Next, the end of the adhesive tape 300 to which the WDe2 single crystal 30B is attached is bonded to the opposite end, and then the process of peeling them off is repeated (Figure 3B). This results in multiple WDe2 film 30A, which are peeled-off pieces of the WDe2 single crystal 30B, being obtained on the adhesive surface of the adhesive tape 300 (Figure 3C). Next, the portion of the adhesive tape 300 to which the WDe2 film 30A is attached is bonded to the substrate 16, and the substrate 16 is heated to a temperature of approximately 60°C (Figure 3D). After that, the adhesive tape 300 is peeled off the substrate 16. This transfers the WDe2 film 30A to the substrate 16 (Figure 3E).

[0020] Next, the WDe2 film 30A is picked up from the substrate 16 using the transfer jig 200 (Figure 2E). The transfer jig 200 has a dome-shaped first resin layer 202 provided on a base 201 and a second resin layer 203 covering the first resin layer 202. For example, glass can be used as the material for the base 201. The first resin layer 202 is made of a resin with a relatively high softening temperature. For example, PDMS (polydimethylsiloxane) can be used as the material for the first resin layer 202. The second resin layer 203 is made of a resin with a relatively low softening temperature. For the material for the second resin layer 203, PS (polystyrene) or PPC (polypropylene carbonate) with a softening temperature of around 80°C can be used. When picking up the WDe2 film 30A using the transfer jig 200, the transfer jig 200 is heated to about 80°C. As a result, the second resin layer 203 softens and becomes viscous. The WTe2 film 30A adheres to the second resin layer 203 and peels off from the substrate 16.

[0021] Next, the WDe2 film 30A picked up using the transfer jig 200 is laminated onto the superconducting electrode 20 (Figures 2F and 2G). The steps of forming the WDe2 film 30A on the substrate 16 (Figure 2D), picking up the WDe2 film 30A from the substrate 16 (Figure 2E), and laminating the WDe2 film 30A onto the superconducting electrode 20 (Figures 2F and 2G) are performed in a glove box purged with an inert gas. This suppresses oxidation of the WDe2 film 30A.

[0022] The superconducting electrode 20 is formed by annealing the alternating Pd·Te multilayer film 23 (Figure 2C) at approximately 180°C to induce solid-phase reactions in the Pd film 21 and Te film 22. The solid-phase reaction of the alternating Pd·Te multilayer film 23 forms the superconducting electrode 20 containing PdTe2 or PdTe (Figure 2F). The annealing process is carried out in a glove box before the WDe2 film 30A is laminated onto the superconducting electrode 20. The superconducting electrode 20 and the WDe2 film 30A are joined by intermolecular forces.

[0023] Next, the transfer jig 200 is heated to approximately 100°C to soften the second resin layer 203. This separates the WDe2 film 30A from the transfer jig 200. By heating to approximately 100°C, the diffusion of Pd contained in the superconducting electrode 20 into the WDe2 film 30A can be avoided, and the properties of the WDe2 film 30A as a topological insulator are maintained. Note that the temperature at which Pd diffusion occurs is 150°C or higher. A portion of the resin constituting the second resin layer 203 remains on the WDe2 film 30A side. This residue 50 functions as a protective film that prevents oxidation of the WDe2 film 30A and the superconducting electrode 20 (Figure 2H). Note that the residue 50 may be removed using an organic solvent such as chloroform.

[0024] As described above, the electronic device 10 according to the embodiment of the disclosed technology comprises a superconducting electrode 20 containing PdTe2 or PdTe, and a TMD film 30 containing transition metal dichalcogenite laminated on the superconducting electrode 20. A method for manufacturing the electronic device 10 according to the embodiment of the disclosed technology includes a step of forming a superconducting electrode 20 containing PdTe2 or PdTe by annealing a film containing Pd and Te (Pd·Te alternating laminated film 23) in an inert gas atmosphere to induce a solid-phase reaction. A method for manufacturing the electronic device 10 also includes a step of laminating the TMD film 30 containing transition metal dichalcogenite and the superconducting electrode 20 in an inert gas atmosphere.

[0025] The inventors focused on the solid-phase reaction between WTe2 and Pd in ​​order to realize a structure in which a superconductor is in contact with a topological insulator. It was known that superconductivity is generated by the junction of WTe2 and Pd, but the mechanism was not clear. Through the inventors' research to date, as shown in Figure 4, it has been revealed that by stacking a WTe2 film 30A on a Pd film 21 and performing an annealing treatment at about 180°C, Pd diffuses into WTe2, causing a solid-phase reaction, and a superconductor 20X containing PdTe or PdTe2 is formed near the interface between the Pd film 21 and the WTe2 film 30A. In this way, a structure in which a topological insulator (WTe2) and a superconductor (PdTe or PdTe2) are in contact can be obtained. However, with this method, when the superconductor 20X is formed on the WTe2 film 30A, the diffusion of Pd at the interface between the WTe2 film 30A and the Pd film 21 impairs the properties of the WTe2 film 30A as a topological insulator.

[0026] According to the electronic device 10 and its manufacturing method as embodiments of the disclosed technology, the Te contained in the superconducting electrode 20, which includes PdTe or PdTe2, is supplied from the Pd·Te alternating laminated film 23. This suppresses the extraction of Te from the TMD film to the Pd film. In other words, a structure in which a topological insulator and a superconductor are in contact can be realized without impairing the topological insulator properties of the TMD film 30.

[0027] Furthermore, by making the outermost surface of the Pd·Te alternating laminated film 23 Pd, oxidation of the Pd·Te alternating laminated film 23 can be suppressed. In addition, the steps of forming the WDe2 film 30A on the substrate 16 (Figure 2D), picking up the WDe2 film 30A from the substrate 16 (Figure 2E), and stacking the WDe2 film 30A on the superconducting electrode 20 (Figures 2F and 2G) are performed in a glove box purged with an inert gas. This suppresses oxidation of the WDe2 film 30A. In other words, according to the manufacturing method of the electronic device 10 of this embodiment, the formation of an oxide film at the interface between the TMD film 30 and the superconducting electrode 20 can be suppressed.

[0028] The above description illustrates the case in which a WDe2 film 30A (TMD film 30) is laminated on a superconducting electrode 20 by transferring a flake of a WDe2 single crystal. However, the disclosed technology is not limited to this embodiment. For example, it is also possible to laminate a WDe2 film 30A (TMD film) on a superconducting electrode 20 using the MBE (Molecular Beam Epitxy) method or the PLD (Pulsed Laser Deposition) method. The MBE method is a physical vapor deposition method in which a raw material is heated by an electron beam under vacuum, and the generated molecular beam is directed to the substrate to grow crystals. The PLD method is a method in which a target is irradiated with a pulsed laser with high power density under vacuum, and the target components are ablated and evaporated to form a thin film.

[0029] Figures 5A to 5C are cross-sectional views showing an example of a method for manufacturing an electronic device 10 using the MBE method or the PLD method. A substrate 15 on which a Pd·Te alternating laminated film 23 is formed is placed in the vacuum chamber of the MBE or PLD apparatus (Figure 5A). Next, in the vacuum chamber, the Pd·Te alternating laminated film 23 is subjected to an annealing treatment at approximately 180°C to induce a solid-phase reaction, thereby forming a superconducting electrode 20 containing PdTe2 or PdTe. After that, a mask 45 having an opening corresponding to the pattern of the WDe2 film 30A is placed in the vacuum chamber (Figure 5B). Next, the WDe2 film 30A is formed on the superconducting electrode 20 using the MBE method or the PLD method (Figure 5C). If necessary, a protective film (not shown) may be formed to cover the superconducting electrode 20 and the WDe2 film 30A.

[0030] [Second Embodiment] Figure 6 is a cross-sectional view showing an example of the configuration of an electronic device 10A according to a second embodiment of the disclosed technology. The electronic device 10A according to this embodiment is a top-contact type device in which a superconducting electrode 20 is provided on a TMD film 30. The superconducting electrode 20 contains PdTe2 or PdTe, and the TMD film 30 contains transition metal dichalcogenite, similar to the electronic device 10 according to the first embodiment. The transition metal dichalcogenite may be a topological insulator, for example, WTe2. The transition metal dichalcogenite constituting the TMD film 30 may be, for example, WSe2, WS2, MoSe2, or MoS2.

[0031] The TMD film 30 has a thickness in the first portion P1, which is the part that contacts the superconducting electrode 20, that is greater than the thickness of the second portion P2, which is the part other than the first portion. The thickness of the second portion P2 of the TMD film 30 is, for example, the thickness of 2 to 4 atomic layers. The surface of the TMD film 30 is oxidized when exposed to the atmosphere and covered with an oxide film 60. In the second portion P2 of the TMD film 30, only the surface layer of the 2 to 4 atomic layers is oxidized. By making the thickness of the second portion P2 of the TMD film 30 the thickness of 2 to 4 atomic layers, at least one layer, including the bottom layer, is maintained in an unoxidized state. The surface of the superconducting electrode 20 may be covered with a Pd film 21.

[0032] The manufacturing method for the electronic device 10A will be described below. Figures 7A to 7F are cross-sectional views showing an example of a manufacturing method for the electronic device 10A.

[0033] First, a multilayer TMD film 30 is formed on the substrate 15. In the following description, the case in which the TMD film 30 is a WTe2 film 30A will be used as an example, but the method described below is also applicable when the TMD film 30 is composed of a transition metal dichalcogenite other than WTe2. The multilayer WTe2 film 30A can be formed by transferring flakes of a WTe2 single crystal, as in the first embodiment, and can also be formed by the MBE method or the PLD method (Figure 7A).

[0034] Next, a Pd film 21 is formed on the surface of the WDe2 film 30A using the lift-off method. The lift-off method patterns the Pd film 21 into the desired shape (Figure 7B). Then, using the Pd film 21 as a mask, the WDe2 film 30A is partially thinned by etching (Figure 7C). The portion of the WDe2 film 30A other than the portion covered by the Pd film 21 (first portion P1) (second portion P2) is thinned to a thickness of 2 to 4 atomic layers. Argon milling or atomic layer etching (ALE) can be used as the etching method for the WDe2 film 30A.

[0035] Figures 8A to 8D are cross-sectional views showing an example of a method for partially thinning the WDe2 film 30A by etching using the ALE method. First, the WDe2 film 30A is subjected to UV ozone treatment using the Pd film 21 as a mask. This oxidizes the outermost layer of the WDe2 film 30A, forming an oxide film 61 on the surface of the WDe2 film 30A (Figure 8A). Since the WDe2 film 30A is damaged by ultraviolet light irradiation, it is preferable to shield it from direct ultraviolet light irradiation.

[0036] Next, the oxide film 61 formed on the surface of the WDe2 film 30A is removed using a KOH ethanol solution. This thins the WDe2 film 30A by the thickness of one atomic layer (Figure 8B). While it is possible to use an aqueous KOH solution to remove the oxide film 61, the WDe2 film 30A would be oxidized by the aqueous solution. Since the removal of the oxide film 61 formed on the surface of the WDe2 film 30A must be carried out in an anhydrous environment, it is preferable to use a KOH ethanol solution.

[0037] Next, the surface of the WDe2 film 30A from which the oxide film 61 has been removed is oxidized again by UV ozone treatment to re-form the oxide film 61 on the surface of the WDe2 film 30A (Figure 8C). Then, the oxide film 61 formed on the surface of the WDe2 film 30A is removed using a KOH ethanol solution (Figure 8D). The process of forming the oxide film 61 on the surface of the WDe2 film 30A and the process of removing the oxide film 61 are repeated until the thickness of the portion of the WDe2 film 30A other than the portion covered by the Pd film 21 (first portion P1) (second portion P2) is equivalent to 2 to 4 atomic layers.

[0038] After the partial thinning of the WTe2 film 30A is completed, the Pd film 21 and the WTe2 film 30A are subjected to an annealing treatment at approximately 180°C. This causes the Pd contained in the Pd film 21 to diffuse into the WTe2 film 30A, and a superconducting electrode 20 containing PdTe or PdTe2 is formed near the interface between the Pd film 21 and the WTe2 film 30A by a solid-phase reaction. Unreacted Pd film 21 remains on the superconducting electrode 20 (Figure 7D). Since the WTe2 film 30A is easily oxidized, an oxide film may exist between the Pd film 21 and the WTe2 film 30A before the annealing treatment. However, the Pd film 21 can diffuse into the WTe2 film 30A by permeating through the oxide film present between it and the WTe2 film 30A. No oxide film is formed at the interface between the superconducting electrode 20, which contains PdTe or PdTe2 formed by the diffusion of the Pd film 21, and the WDe2 film 30A. Furthermore, the area directly beneath the Pd film 21 in the WDe2 film 30A may be destroyed by Pd diffusion. However, since Pd does not diffuse into the thinned portion (second portion P2) of the WDe2 film 30A, the properties of the WDe2 film 30A as a topological insulator are maintained.

[0039] Subsequently, the outermost layer of the WTe2 film 30A is oxidized by exposure to the atmosphere, forming an oxide film 60. However, at least one layer of the WTe2 film 30A, including the bottom layer, remains unoxidized (Figure 7E).

[0040] Furthermore, after forming the superconducting electrode 20 and before exposing the WDe2 film 30A to the atmosphere, a cap film 55 may be formed to cover the Pd film 21, the superconducting electrode 20, and the WDe2 film 30A (Figure 7F). The cap film 55 may be made of, for example, hexagonal boron nitride. By providing the cap film 55, oxidation of the WDe2 film 30A can be prevented. In a configuration including the cap film 55, it becomes unnecessary to anticipate oxidation of the WDe2 film 30A, and the thickness of the portion of the WDe2 film 30A other than the portion covered by the Pd film 21 (first portion P1) (second portion P2) can be made to the thickness of one atomic layer.

[0041] As described above, the electronic device 10A according to the second embodiment of the disclosed technology is a top-contact type device in which a superconducting electrode 20 is provided on a TMD film 30. The thickness of the first portion P2 of the TMD film 30, which is the part in contact with the superconducting electrode 20, is greater than the thickness of the second portion P2, which is the part of the TMD film 30 other than the first portion P1.

[0042] A method for manufacturing an electronic device 10A according to a second embodiment of the disclosed technology includes the steps of forming a Pd film 21 on the surface of a multilayer TMD film 30 containing Te, and partially thinning the TMD film 30 by etching the TMD film 30 using the Pd film 21 as a mask. The method for manufacturing the electronic device 10A also includes the step of forming a superconducting electrode containing PdTe2 or PdTe near the interface between the Pd film 21 and the TMD film 30 by annealing the Pd film 21 and the TMD film 30 to induce a solid-phase reaction.

[0043] According to the electronic device 10A and its manufacturing method according to this embodiment, the portion of the WDe2 film 30A directly beneath the Pd film 21 may be destroyed by the diffusion of the Pd film 21. However, since Pd does not diffuse into the thinned portion (second portion P2) of the WDe2 film 30A, the properties of the WDe2 film 30A as a topological insulator are maintained. Furthermore, no oxide film is formed at the interface between the superconducting electrode 20, which includes PdTe or PdTe2 formed by the diffusion of the Pd film 21, and the WDe2 film 30A. In other words, according to the manufacturing method of the electronic device 10A according to this embodiment, the formation of an oxide film at the interface between the TMD film 30 (WTe2) and the superconducting electrode 20 (PdTe or PdTe2) can be suppressed.

[0044] In the above description, an example was given in which a superconducting electrode 20 containing PdTe or PdTe2 is formed using a Pd film 21 formed on the surface of a WTe2 film 30A. However, a Pd·Te alternating multilayer film may be used instead of the Pd film 21. Figures 9A to 9D are cross-sectional views showing an example of a manufacturing method when a superconducting electrode 20 is formed using a Pd·Te alternating multilayer film 23.

[0045] A Pd·Te alternating multilayer film 23 is formed on the surface of the WTe2 film 30A using the lift-off method. To minimize surface oxidation, the uppermost layer of the Pd·Te alternating multilayer film 23 is preferably Pd. Furthermore, to promote the diffusion of Pd into the WTe2 film 30A, the bottommost layer of the Pd·Te alternating multilayer film 23 is also preferably Pd. By lift-off, the Pd·Te alternating multilayer film 23 is patterned into the desired shape (Figure 9A).

[0046] Next, the WDe2 film 30A is partially thinned by etching it using the Pd·Te alternating multilayer film 23 as a mask (Figure 9B). The portion of the WDe2 film 30A other than the portion covered by the Pd·Te alternating multilayer film 23 (first portion P1) (second portion P2) is thinned to a thickness of 2 to 4 atomic layers. Argon milling or atomic layer etching (ALE) can be used as the etching method for the WDe2 film 30A.

[0047] After the partial thinning of the WTe2 film 30A is completed, the Pd·Te alternating multilayer film 23 and the WTe2 film 30A are subjected to annealing at approximately 180°C. This causes a solid-phase reaction within the Pd·Te alternating multilayer film 23, forming PdTe or PdTe2. Pd also diffuses into the WTe2 film 30A, and PdTe or PdTe2 is formed near the interface between the Pd·Te alternating multilayer film 23 and the WTe2 film 30A by solid-phase reaction. The superconducting electrode 20 is formed by the PdTe or PdTe2 produced by the solid-phase reaction (Figure 9C). No oxide film is formed at the interface between the superconducting electrode 20, which contains PdTe or PdTe2 formed by Pd diffusion, and the WTe2 film 30A. Furthermore, the WTe2 film 30A directly beneath the Pd·Te alternating multilayer film 23 can be destroyed by Pd diffusion. However, since Pd does not diffuse into the thinned portion (second portion P2) of the WDe2 film 30A, the properties of the WDe2 film 30A as a topological insulator are maintained.

[0048] Subsequently, the outermost layer of the WTe2 film 30A is oxidized by exposure to the atmosphere, forming an oxide film 60. However, at least one layer of the WTe2 film 30A, including the bottom layer, remains unoxidized (Figure 9D).

[0049] [Third Embodiment] Figure 10 is a plan view showing an example of the configuration of an electronic device 10B according to a third embodiment of the disclosed technology. The electronic device 10B functions as a qubit element using Majorana particles. The electronic device 10B includes a first TMD film 30P, a second TMD film 30Q, superconducting electrodes 20A, 20B, 20C, and magnetic materials 70A, 70B, 70C, 70D. The first TMD film 30P and the second TMD film 30Q are composed of a topological insulator, which may be, for example, a single-layer WTe2 film. The superconducting electrodes 20A to 20C are composed of a superconductor containing PdTe2 or PdTe.

[0050] The first TMD film 30P and the second TMD film 30Q are each patterned in a rectangular shape. The first TMD film 30P is positioned with its longitudinal direction oriented horizontally. The second TMD film 30Q is positioned with its longitudinal direction oriented vertically and is laminated on the first TMD film 30P, intersecting it. The long edge E1 of the first TMD film 30P and the long edge E2 of the second TMD film 30Q intersect.

[0051] The superconducting electrodes 20A and 20B are provided in contact with the long edge E1 of the first TMD film 30P. The superconducting electrode 20C is provided in contact with the long edge E2 of the second TMD film 30Q. The superconducting electrodes 20A to 20C are each patterned in a rectangular shape, and one of their short edges is located near the intersection of the long edge E1 of the first TMD film 30P and the long edge E2 of the second TMD film 30Q. The superconducting electrode 20A is provided in contact with the edge of the first TMD film 30P that forms the corner in contact with the second TMD film 30Q. The electronic device 10B is a bottom-contact type in which the first TMD film 30P and the second TMD film 30Q are laminated on the superconducting electrodes 20A to 20C.

[0052] Magnetic material 70A is in contact with the long edge E1 of the first TMD film 30P and is located near the other short edge of the superconducting electrode 20A. Magnetic material 70B is in contact with the long edge E1 of the first TMD film 30P and is located near the other short edge of the superconducting electrode 20B. Magnetic material 70C is in contact with the long edge E2 of the second TMD film 30Q and is located near the other short edge of the superconducting electrode 20C. Magnetic material 70D is located near the intersection of the long edge E1 of the first TMD film 30P and the long edge E2 of the second TMD film 30Q. For example, Ni, Co, or Fe can be used as magnetic materials 70A to 70D.

[0053] Superconducting electrodes 20A, 20B, and 20C are connected to superconducting wirings 71A, 71B, and 71C, respectively. The superconducting wirings 71A, 71B, and 71C may each be composed of a superconductor containing PdTe2 or PdTe, similar to the superconducting electrodes 20A, 20B, and 20C. Alternatively, the superconducting wirings 71A, 71B, and 71C may have a two-layer structure, for example, a stacked PdTe2 and Al, or a two-layer structure, a stacked NbTe2 and Nb. Switches 72A, 72B, and 72C are provided along the respective paths of the superconducting wirings 71A, 71B, and 71C. The switches 72A, 72B, and 72C may be Josephson junctions. The switches 72A, 72B, and 72C are each connected to ground potential.

[0054] According to the electronic device 10B of this embodiment, Majorana particles 100 are generated at the long edge E1 of the first TMD film 30P between the superconducting electrode 20A and the magnetic material 70A, at the intersection with the long edge E2 of the second TMD film 30Q, and at the position between the superconducting electrode 20B and the magnetic material 70B. Majorana particles 100 are also generated at the long edge E2 of the second TMD film 30Q between the superconducting electrode 20C and the magnetic material 70C. The Majorana particles 100 can be localized by the magnetic materials 70A to 70D. By turning switches 72A, 72B, and 72C on and off, the superconducting electrodes 20A, 20B, and 20C can be grounded or floated, making it possible to exchange the Majorana particles 100 generated at each location with each other.

[0055] [Fourth Embodiment] Figure 11 is a plan view showing an example of the configuration of an electronic device 10C according to a fourth embodiment of the disclosed technology. The electronic device 10C functions as a qubit element using Majorana particles. The electronic device 10C comprises a first TMD film 30P, a second TMD film 30Q, superconducting electrodes 20A, 20B, 20C, and magnetic materials 70A, 70B, 70C, 70D. The first TMD film 30P and the second TMD film 30Q are composed of a topological insulator, which may be, for example, a single-layer WTe2 film. The superconducting electrodes 20A to 20C are composed of a superconductor containing PdTe2 or PdTe.

[0056] The first TMD film 30P and the second TMD film 30Q are each patterned in a quadrilateral shape. The first TMD film 30P and the second TMD film 30Q only need to have at least one corner, and may have polygonal shapes other than quadrilaterals or other shapes. One corner of the second TMD film 30Q is in contact with one corner of the first TMD film 30P. The superconducting electrode 20A is provided in contact with the edge of the first TMD film 30P that forms the corner in contact with the second TMD film 30Q. The superconducting electrode 20B is provided in contact with one edge of the second TMD film 30Q that forms the corner in contact with the first TMD film 30P. The superconducting electrode 20C is provided in contact with the other edge of the second TMD film 30Q that forms the corner in contact with the first TMD film 30P. The electronic device 10C is a top-contact type in which superconducting electrodes 20A to 20C are stacked on a first TMD film 30P and a second TMD film 30Q.

[0057] Magnetic material 70A is in contact with the edge of the first TMD film 30P that forms a corner in contact with the second TMD film 30Q, and is located near the superconducting electrode 20A. Magnetic material 70B is in contact with one edge of the second TMD film 30Q that forms a corner in contact with the first TMD film 30P, and is located near the superconducting electrode 20B. Magnetic material 70C is in contact with the other edge of the second TMD film 30Q that forms a corner in contact with the first TMD film 30P, and is located near the superconducting electrode 20C. Magnetic material 70D is located near the corner where the first TMD film 30P and the second TMD film 30Q are in contact with each other.

[0058] Superconducting electrodes 20A, 20B, and 20C are connected to superconducting wirings 71A, 71B, and 71C, respectively. The superconducting wirings 71A, 71B, and 71C may each be composed of a superconductor containing PdTe2 or PdTe, similar to the superconducting electrodes 20A, 20B, and 20C. Alternatively, the superconducting wirings 71A, 71B, and 71C may have a two-layer structure, for example, a stacked PdTe2 and Al, or a two-layer structure, a stacked NbTe2 and Nb. Switches 72A and 72B are provided on the respective paths of the superconducting wirings 71A and 71B. Switches 72A and 72B may be Josephson junctions. Switches 72A and 72B and the superconducting wiring 71C are each connected to ground potential.

[0059] According to the electronic device 10C of this embodiment, Majorana particles 100 are generated at the position between the superconducting electrode 20A and the magnetic material 70A at the edge of the first TMD film 30P that forms a corner in contact with the second TMD film 30Q. Majorana particles 100 are also generated between the superconducting electrode 20B and the magnetic material 70B at one edge of the second TMD film 30Q that forms a corner in contact with the first TMD film 30P. Furthermore, Majorana particles 100 are generated between the superconducting electrode 20C and the magnetic material 70C at the other edge of the second TMD film 30Q that forms a corner in contact with the first TMD film 30P. In addition, Majorana particles 100 are generated at the corners where the first TMD film 30P and the second TMD film 30Q are in contact with each other. The Majorana particles 100 can be localized by the magnetic materials 70A to 70D. By switching switches 72A and 72B on and off, the superconducting electrodes 20A and 20B can be grounded or floated, making it possible to exchange Majorana particles 100 generated at each location with one another. [Explanation of Symbols]

[0060] 10, 10A, 10B, 10C Electronic Devices 20, 20A, 20B, 20C superconducting electrodes 30 TMD membrane 30P First TMD film 30Q Second TMD film 71A, 71B, 71C Superconducting Wiring 72A, 72B, 72C switches

Claims

1. PdTe ２ Or a superconducting electrode containing PdTe, A transition metal dichalcogenite film stacked on the superconducting electrode, It has, The transition metal dichalcogenite film has a thickness in the first portion, which is the part that contacts the superconducting electrode, that is greater than the thickness in the second portion, which is the part other than the first portion. Electronic devices.

2. A superconducting electrode comprising PdTe2 or PdTe, A transition metal dichalcogenite film stacked on the superconducting electrode, It has, The transition metal dichalcogenite film includes a first transition metal dichalcogenite film having at least one corner, and a second transition metal dichalcogenite film having at least one corner, with one corner in contact with one corner of the first transition metal dichalcogenite film. Multiple superconducting electrodes are provided in contact with the edges of the first transition metal dichalcogenite film that form a corner in contact with the second transition metal dichalcogenite film, and the edges of the second transition metal dichalcogenite film that form a corner in contact with the first transition metal dichalcogenite film. Electronic devices.

3. The transition metal dichalcogenite film is a topological insulator film. The electronic device according to claim 1 or claim 2.

4. The transition metal dichalcogenite film is WTe ２ It is a membrane. The electronic device according to claim 3.

5. The transition metal dichalcogenite film is a film consisting of a single-layer or multi-layer atomic layer material. The electronic device according to claim 1 or claim 2.

6. The transition metal dichalcogenite film includes a first transition metal dichalcogenite film and a second transition metal dichalcogenite film laminated on the first transition metal dichalcogenite film while intersecting it. Multiple superconducting electrodes are provided in contact with the intersecting edges of the first transition metal dichalcogenite film and the second transition metal dichalcogenite film. The electronic device according to claim 1.

7. A superconducting wiring connected to each of the multiple superconducting electrodes, A switch provided on each path of the superconducting wiring, Includes The electronic device according to claim 2 or claim 6.

8. PdTe ２ Alternatively, a step of forming a superconducting electrode containing PdTe, A step of stacking a transition metal dichalcogenite film and the superconducting electrode, Includes, The process of forming the superconducting electrode is carried out by forming a Te film, forming a Pd film in contact with the Te film, and annealing the Te film and the Pd film to induce a solid-phase reaction. A method for manufacturing electronic devices.

9. The annealing process is carried out in a vacuum or in an inert gas atmosphere. The process of laminating the transition metal dichalcogenite film and the superconducting electrode is carried out in a vacuum or in an inert gas atmosphere. A method for manufacturing an electronic device according to claim 8.

10. A step of forming a Pd film on the surface of a multilayer transition metal dichalcogenite film containing Te, A step of partially thinning the transition metal dichalcogenite film by etching the transition metal dichalcogenite film using the Pd film as a mask, By annealing the Pd film and the transition metal dichalcogenite film to induce a solid-phase reaction, PdTe is formed at the interface between the Pd film and the transition metal dichalcogenite film. ２ Alternatively, a step of forming a superconducting electrode containing PdTe, A method for manufacturing electronic devices, including

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