A josephson junction, a method of manufacturing the same, and a superconducting device

Abstract

The application provides a Josephson junction, a preparation method thereof and a superconducting device. The Josephson junction comprises a substrate, a first superconducting electrode layer embedded in the substrate, and an upper surface of the first superconducting electrode layer exposed from the substrate, a barrier layer comprising a two-dimensional topological single-crystal material with a tilted Weyl cone, arranged on the substrate and directly in contact with part of the upper surface of the first superconducting electrode layer, a metal protection layer arranged on the substrate and extending to the barrier layer, covering at least part of the upper surface of the barrier layer, and a second superconducting electrode layer arranged on the metal protection layer and electrically connected to the barrier layer through the metal protection layer. The application realizes high-transparent interface contact between the superconducting electrode and the barrier layer; the Josephson junction exhibits an alternating-current Josephson response in a wide frequency band of 15.8-360 GHz; the strong nonlinear photoelectric response and the wide-band light-matter coupling characteristics of the tilted Weyl cone in the barrier layer enable the Josephson junction to exhibit enhanced photoelectric detection performance under terahertz irradiation.

Description

Technical Field

[0001] This invention belongs to the field of superconducting device technology, specifically relating to a Josephson junction, its fabrication method, and a superconducting device. Background Technology

[0002] The terahertz band (0.1-10 THz), as the "electromagnetic gap" connecting microwaves and infrared, is a key technological breakthrough for fields such as astronomical observation, 6G communication, and biomedical imaging. Josephson junctions, with their quantum tunneling effect and strong nonlinear characteristics, have become the core device for solving the problem of high-sensitivity detection in this band. Traditional thin-film Josephson junctions (such as niobium-based SIS structures and high-temperature superconducting double crystal junctions) achieve terahertz signal response through the cooperative tunneling of Cooper pairs and quasiparticles, and have demonstrated core value in ground-based large submillimeter-wave telescopes and other equipment. However, their development is limited by inherent defects: stringent lattice matching requirements lead to many interface defects, making it difficult to miniaturize the device size, and the balance between temperature stability and detection bandwidth is difficult to optimize. Therefore, they cannot meet the requirements of next-generation detectors for response speed and background-limited sensitivity.

[0003] Against this backdrop, Josephson devices based on two-dimensional materials have become an important choice for technological breakthroughs. Two-dimensional materials (such as graphene and transition metal dichalcogenides NbSe2) possess advantages such as atomically flat interfaces, excellent carrier transport properties, and flexible van der Waals stacking. They can not only overcome the lattice matching limitations of traditional thin films but also achieve efficient control of the superconducting nearest neighbor effect through precise control of layer thickness and heterostructure. For example, Miao et al. (DOI:10.1016 / j.carbon.2022.11.040) developed a Josephson junction with a superconductor-graphene-superconductor (SGS) structure integrating a self-complementary logarithmic spiral antenna and an elliptical silicon lens, achieving efficient terahertz coupling with a noise equivalent power (NEP) as low as 2.5-5 × 10⁻⁵ in the 1.4 THz band. -16 W / Hz 1 / 2 This precisely matches the extreme requirements of ground-based astronomical observations. Simultaneously, two-dimensional material heterojunctions can achieve wafer-level large-scale fabrication through a "high-to-low" stacking strategy and can flexibly construct multi-component composite structures. This provides the possibility for the cascaded amplification and multi-functional integration of Josephson junction arrays, thereby promoting the deep application of terahertz detection technology from basic scientific research to industrial scenarios such as security inspection and quantum sensing. Therefore, its controllable fabrication is a key prerequisite for unlocking the full-scenario application of terahertz technology.

[0004] Topological half-metals (e.g., type II and type III Weyl half-metals), with their unique electronic band structure—the strong nonlinear optical response imparted by the tilted Weyl cone and the topological protection properties provided by the Fermi arc surface states—have a natural strong coupling effect with terahertz waves, enabling them to efficiently absorb terahertz photons. This provides an ideal material platform for developing high-performance terahertz detection devices. More importantly, integrating topological single crystals with tilted Weyl cones into superconducting Josephson junctions can achieve synergistic complementarity of the advantages of the two materials: retaining the unique advantages of topological half-metal single crystals such as strong light-matter interaction and broad spectral response, while inheriting the inherent core characteristics of Josephson junctions such as high sensitivity, low noise, and fast response, providing a new technical path to overcome the performance bottlenecks of existing superconducting terahertz devices.

[0005] However, the integration of topological semimetals and superconducting Josephson junctions still faces technical challenges such as heterogeneous interface compatibility, synergistic regulation of topological and superconducting properties, and optimization of integration processes. Specifically, these challenges include: 1) Difficulty in achieving low-resistance contact between superconducting electrodes and two-dimensional materials: The interface between superconducting electrodes and two-dimensional materials is prone to oxidation reactions to form an insulating layer. Furthermore, the integration between the two generates interfacial stress and defects, leading to a significant increase in contact resistance and making it impossible to form an ideal ohmic contact. This directly restricts the improvement of device detection sensitivity and makes it difficult to meet the requirements for detecting weak terahertz signals; 2) Insufficient compatibility between device fabrication processes and existing micro / nano fabrication technologies: The mechanical brittleness and chemical sensitivity of two-dimensional materials conflict with the compatibility of traditional micro / nano fabrication processes such as photolithography, etching, and coating. This can easily lead to material damage or performance degradation, becoming a major technical obstacle to large-scale mass production.

[0006] Therefore, overcoming the technical bottlenecks such as poor compatibility of heterogeneous interfaces and difficulty in synergistic control of topological and superconducting properties during the integration of topological semimetals and superconducting Josephson junctions has become a core problem that urgently needs to be solved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a Josephson junction, its fabrication method, and a superconducting device. This invention introduces a two-dimensional topological semi-metallic single-crystal material with tilted Weyl cones as a barrier layer into the Josephson junction. Simultaneously, a metal protective layer is introduced to separate the second superconducting electrode layer and the barrier layer, achieving a highly transparent interface contact between the superconducting electrode and the barrier layer, significantly reducing contact resistance. The Josephson junction exhibits a wide-bandwidth AC Josephsonson response of 15.8-360 GHz. Furthermore, the strong nonlinear photoelectric response and wide-bandwidth light-matter coupling characteristics imparted by the tilted Weyl cones in the barrier layer enable the Josephson junction to exhibit significantly enhanced photoelectric detection performance under terahertz irradiation, providing a novel and promising technical route for the industrialization of high-performance terahertz detectors.

[0008] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a Josephson node, the Josephson node comprising: Substrate.

[0009] A first superconducting electrode layer is embedded in the substrate, and the upper surface of the first superconducting electrode layer is exposed from the substrate.

[0010] A barrier layer comprising a two-dimensional topological single-crystal material having an inclined Weyl cone; the barrier layer is disposed on the substrate and is in direct contact with a portion of the upper surface of the first superconducting electrode layer.

[0011] A metal protective layer is disposed on the substrate and extends to the barrier layer, covering at least a portion of the upper surface of the barrier layer.

[0012] The second superconducting electrode layer is disposed on the metal protective layer and is electrically connected to the barrier layer through the metal protective layer.

[0013] This invention introduces a two-dimensional topological semi-metallic single-crystal material with tilted Weyl cones as a barrier layer into the Josephson junction. Simultaneously, a metal protective layer is introduced to separate the second superconducting electrode layer and the barrier layer, achieving a highly transparent interface contact between the superconducting electrode and the barrier layer, significantly reducing contact resistance. The Josephson junction exhibits a wide-bandwidth AC Josephsonson response of 15.8-360 GHz. Furthermore, the strong nonlinear photoelectric response and wide-bandwidth light-matter coupling characteristics imparted by the tilted Weyl cones in the barrier layer enable the Josephson junction to exhibit significantly enhanced photoelectric detection performance under terahertz irradiation, providing a novel and promising technical route for the industrialization of high-performance terahertz detectors.

[0014] In this invention, the barrier layer comprises a two-dimensional topological single-crystal material with an inclined Weyl cone. The "inclined Weyl cone" refers to the point in the electronic band structure of the two-dimensional topological single-crystal material where the bottom of the conduction band and the top of the valence band near the Fermi level come into contact at the Weyl point in momentum space, forming a band crossing point with a linear dispersion relationship. The linear dispersion band near this band crossing point is tilted along a specific direction in momentum space, and the conduction band and valence band exhibit an asymmetric distribution relative to the zero energy point.

[0015] Preferably, the two-dimensional topological single crystal material includes any one of NbIrTe4, TaIrTe4, or WTe2.

[0016] Preferably, the AB plane of the two-dimensional topological single crystal material is parallel to the substrate surface.

[0017] In this invention, the AB plane of the two-dimensional topological single crystal material is parallel to the substrate surface, which is beneficial for the dissociation of the two-dimensional single crystal and the acquisition of a high-quality thin layer.

[0018] It should be noted that "AB plane" refers to the plane containing the atomic layers of a two-dimensional topological single-crystal material. When the AB plane is parallel to the substrate surface, it means that the material is laid flat on the substrate, and its thickness direction (c-axis) is perpendicular to the substrate.

[0019] Preferably, the thickness of the barrier layer is less than the sum of the coherence lengths of the first superconducting electrode and the second superconducting electrode.

[0020] It should be noted that "coherence length" refers to the maximum characteristic length of Cooper pairs in a superconducting electrode that maintains quantum phase coherence in space.

[0021] For example, the thickness of the barrier layer in this invention can be 2-20nm, such as 2nm, 3nm, 4nm, 5nm, 10nm or 20nm.

[0022] Preferably, the material of the metal protective layer includes aluminum or titanium.

[0023] Preferably, the thickness of the metal protective layer is 1-2 nm, for example, it can be 1 nm, 1.5 nm or 2 nm.

[0024] This invention employs a metal protective layer of appropriate thickness, which can effectively reduce the bombardment damage of high-energy particles to the surface of the barrier layer and ensure the interface quality of the junction region.

[0025] Preferably, the substrate is a silicon-based substrate. For example, it may be a Si / SiO2 substrate, etc.

[0026] Preferably, the superconducting material of the first superconducting electrode layer includes any one of niobium, niobium nitride, or niobium titanium nitride.

[0027] Preferably, the thickness of the first superconducting electrode layer is 30-80 nm, for example, it can be 30 nm, 40 nm, 50 nm, 60 nm, 70 nm or 80 nm.

[0028] Preferably, the superconducting material of the second superconducting electrode layer includes any one or a combination of at least two of niobium, niobium nitride, or niobium titanium nitride.

[0029] Preferably, the thickness of the second superconducting electrode layer is 100-150 nm, for example, it can be 100 nm, 110 nm, 120 nm, 130 nm, 140 nm or 150 nm.

[0030] Preferably, the vertical projection of the electrical connection region between the second superconducting electrode layer and the barrier layer on the substrate does not overlap with the first superconducting electrode layer, and the width of the vertical projection is 80nm-30μm, for example, it can be 80nm, 100nm, 250nm, 500nm, 750nm, 1μm, 5μm, 10μm, 15μm, 20μm, 25μm or 30μm, etc.

[0031] In a second aspect, the present invention provides a method for preparing a Josephson knot as described in the first aspect, the method comprising the following steps: A substrate is provided in which an embedded first superconducting electrode layer is formed, such that the upper surface of the first superconducting electrode layer is exposed from the substrate.

[0032] A two-dimensional topological single-crystal material with an inclined Weyl cone is transferred to a predetermined region on the substrate and the first superconducting electrode layer to form a barrier layer.

[0033] A metal protective layer and a second superconducting electrode layer are sequentially deposited on the substrate and the barrier layer.

[0034] The metal protective layer and the second superconducting electrode layer are selectively etched to remove portions of the second superconducting electrode layer and the metal protective layer outside a predetermined region, thereby obtaining the Josephson junction.

[0035] The preparation process provided by this invention is highly compatible with existing micro-nano fabrication technologies, fundamentally avoiding the conflicts that exist in the micro-nano fabrication process of two-dimensional topological semi-metallic single crystals, improving the structural stability of the barrier layer in subsequent processes, and removing the main technical obstacles to large-scale mass production.

[0036] Preferably, the method for forming the embedded first superconducting electrode layer includes: A first photoresist layer is deposited on a substrate, and then the first photoresist layer is subjected to ultraviolet lithography to form a first superconducting electrode pattern.

[0037] The substrate of the exposed area in the first superconducting electrode pattern is etched, and then the first superconducting electrode material is deposited. Subsequently, the first superconducting electrode material and the first photoresist layer covering the first photoresist layer are removed by a lift-off process to obtain the embedded first superconducting electrode layer.

[0038] Preferably, the deposition method of the metal protective layer includes electron beam evaporation or molecular beam epitaxy.

[0039] It should be noted that molecular beam epitaxy is a physical deposition technique for compound semiconductor multilayer thin films. Its basic principle is to heat the elements that make up the thin film in their respective molecular beam furnaces under ultra-high vacuum conditions to form directional molecular beams that are incident on a heated substrate to grow the thin film.

[0040] Preferably, the deposition method of the second superconducting electrode layer includes magnetron sputtering.

[0041] Preferably, the selective etching method includes: A second photoresist layer is deposited on the upper surface of the second superconducting electrode layer, and the junction region of the Josephson junction and the pattern of the second superconducting electrode are formed by photolithography; reactive ion etching is performed to remove the second superconducting electrode material other than the junction region of the Josephson junction and the pattern of the second superconducting electrode.

[0042] Remove the second photoresist layer, and then etch away the junction region of the Josephson junction and the metal protective layer other than the second superconducting electrode pattern. For example, depending on the properties of the protective layer metal, such as aluminum: ion beam etching for 2 seconds or immersion in a weakly alkaline solution (e.g., AZ 300MIF (developer of AZ1500)) for 3 seconds; titanium: ion beam etching for 2 seconds.

[0043] Preferably, the preparation method includes the following steps: A silicon substrate is provided, a first photoresist layer is spin-coated and deposited on the silicon substrate, and the first photoresist layer is subjected to ultraviolet lithography to form a first superconducting electrode pattern.

[0044] Reactive ion etching is performed on the silicon substrate in the exposed area of ​​the first superconducting electrode pattern. A first superconducting electrode material with the same thickness as the etching depth is deposited by magnetron sputtering. The first superconducting electrode material and the first photoresist layer covering the first photoresist layer are removed by a lift-off process to form a patterned electrode structure. The oxide layer generated on the electrode surface is removed to obtain the embedded first superconducting electrode layer.

[0045] A two-dimensional topological semimetal single crystal material with an inclined Weyl cone is provided, and the two-dimensional topological semimetal single crystal material is positioned and transferred to a predetermined region on the substrate and the first superconducting electrode layer to form a barrier layer.

[0046] A metal protective layer is deposited on the silicon substrate and the barrier layer using electron beam evaporation, and a second superconducting electrode layer is deposited using magnetron sputtering.

[0047] A second photoresist layer is spin-coated and deposited on the second superconducting electrode layer, and the junction region of the Josephson junction and the pattern of the second superconducting electrode are formed by photolithography; reactive ion etching is performed to remove the second superconducting electrode material other than the junction region of the Josephson junction and the pattern of the second superconducting electrode.

[0048] The second photoresist layer is removed, and then the junction region of the Josephson junction and the metal protective layer outside the second superconducting electrode pattern are removed by dry etching or wet etching to obtain the Josephson junction.

[0049] Preferably, during the reactive ion etching process on the silicon substrate in the exposed area of ​​the first superconducting electrode pattern, the parameters of the reactive ion etching include: the etching gas includes CF4 gas, the etching power is 100W, the etching time is 3-7min (e.g., 3min, 4min, 5min, 6min or 7min, etc.), and the etching depth is 30-80nm (e.g., 30nm, 40nm, 50nm, 60nm, 70nm or 80nm, etc.).

[0050] Preferably, in the magnetron sputtering method for depositing the first superconducting electrode layer, the parameters include: sputtering power of 180-200W (e.g., 180W, 190W, or 200W), deposition gas pressure of 1.8-2.2mTorr (e.g., 1.8mTorr, 1.9mTorr, 2mTorr, 2.1mTorr, or 2.2mTorr), and sample distance from the target material of 6cm.

[0051] Preferably, in the magnetron sputtering method for depositing the second superconducting electrode layer, the parameters include: sputtering power of 80-100W (e.g., 80W, 90W, or 100W), deposition gas pressure of 5-8mTorr (e.g., 5mTorr, 6mTorr, 7mTorr, or 8mTorr), and a sample distance of 10cm from the target.

[0052] Preferably, during the reactive ion etching process to remove the junction region of the Josephson junction and the second superconducting electrode material other than the second superconducting electrode pattern, the etching gas used in the reactive ion etching includes SF6 gas, and the etching time is 120-180 s (e.g., 120 s, 130 s, 140 s, 150 s, 160 s, 170 s, or 150 s, etc.). In a third aspect, the present invention provides a superconducting device comprising the Josephson junction as described in the first aspect.

[0053] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0054] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention introduces a two-dimensional topological semi-metallic single crystal material with tilted Weyl cones as a barrier layer into the Josephson junction, and introduces a metal protective layer to separate the second superconducting electrode layer and the barrier layer, thereby achieving a highly transparent interface contact between the superconducting electrode and the barrier layer and significantly reducing the contact resistance. The Josephson junction exhibits a wide-band AC Josephson response of 15.8-360 GHz. At the same time, the strong nonlinear photoelectric response and wide-band light-matter coupling characteristics endowed by the tilted Weyl cones in the barrier layer enable the Josephson junction to exhibit significantly enhanced photoelectric detection performance under terahertz irradiation, providing a novel and promising technical route for the industrialization of high-performance terahertz detectors.

[0055] (2) The preparation process provided by the present invention is highly compatible with existing micro-nano processing technology, fundamentally avoiding the conflict between two-dimensional topological semi-metal single crystals in micro-nano processing, improving the structural stability of the barrier layer in subsequent processes, and eliminating the main technical obstacles to large-scale mass production. Attached Figure Description

[0056] Figure 1 This is a top view of the Josephson knot provided in Embodiment 1 of the present invention.

[0057] Figure 2 This is a schematic diagram of the product after step (1) in Embodiment 1 of the present invention.

[0058] Figure 3 This is a schematic diagram of the product after step (2) in Embodiment 1 of the present invention.

[0059] Figure 4 This is a schematic diagram of the product after step (3) in Embodiment 1 of the present invention.

[0060] Figure 5 This is a schematic diagram of the product after step (4) in Embodiment 1 of the present invention.

[0061] Figure 6 This is a schematic diagram of the product after step (5) in Embodiment 1 of the present invention.

[0062] Figure 7 This is a schematic diagram of the product after step (6) in Embodiment 1 of the present invention.

[0063] Figure 8 The resistance-temperature curve of the Josephson junction during the cooling process provided in Embodiment 1 of the present invention.

[0064] Figure 9 The current-voltage characteristic curve of the Josephson junction at T=3.2K is provided in Embodiment 1 of the present invention.

[0065] Figure 10The voltage-current characteristic curve of the Josephson junction under microwave irradiation is provided in Embodiment 1 of the present invention.

[0066] Wherein, 1-silicon substrate; 2-first superconducting electrode layer; 3-barrier layer; 4-metal protective layer; 5-second superconducting electrode layer; 6-first photoresist layer; 7-second photoresist layer. Detailed Implementation

[0067] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0068] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0069] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0070] Example 1 This embodiment provides a Josephson knot, as shown in the top view diagram of the Josephson knot. Figure 1 As shown, it includes: A silicon-based substrate, wherein the silicon-based substrate is a Si / SiO2 substrate.

[0071] A first superconducting electrode layer 2 is embedded in the silicon substrate, and the upper surface of the first superconducting electrode layer 2 is exposed from the silicon substrate.

[0072] The barrier layer comprises a two-dimensional topological single crystal material with an inclined Weyl cone; the barrier layer 3 is disposed on the silicon substrate and is in direct contact with a portion of the upper surface of the first superconducting electrode layer.

[0073] A metal protective layer is disposed on the silicon substrate and extends to the barrier layer, covering a portion of the upper surface of the barrier layer.

[0074] The second superconducting electrode layer 5 is disposed on the metal protective layer and is electrically connected to the barrier layer through the metal protective layer.

[0075] The two-dimensional topological single crystal material is NbIrTe4, and the AB plane of the two-dimensional topological single crystal material is parallel to the surface of the silicon substrate. The thickness of the barrier layer is 5 nm, which is less than the sum of the coherence lengths of the first superconducting electrode and the second superconducting electrode. The width of the region in direct contact between the barrier layer and the upper surface of the first superconducting electrode layer 2 is 6 μm. The material of the metal protective layer is aluminum, and the thickness is 1 nm. The superconducting material of the first superconducting electrode layer 2 is niobium, and the thickness is 60 nm. The superconducting material of the second superconducting electrode layer 5 is niobium, and the thickness is 120 nm. The vertical projection of the electrical connection region between the second superconducting electrode layer 5 and the barrier layer on the silicon substrate does not overlap with the first superconducting electrode layer 2, and the width of the vertical projection is 2 μm.

[0076] This embodiment also provides a method for preparing the above-mentioned Josephson knot, the method comprising the following steps: (1) Provide a silicon substrate 1, and use acetone, alcohol and deionized water in sequence to ultrasonically clean the surface of the silicon substrate 1 to remove organic pollutants, particles and other surface impurities; the silicon substrate 1 is a Si / SiO2 substrate.

[0077] A first photoresist layer 6 is spin-coated and deposited on the surface of the cleaned silicon substrate 1, and then the first photoresist layer 6 is subjected to ultraviolet lithography and developed to form a first superconducting electrode pattern; the material of the first photoresist layer 6 is LOR10B+AZ1500.

[0078] The product illustration after step (1) is as follows: Figure 2 As shown.

[0079] (2) Reactive ion etching is performed on the silicon substrate 1 of the exposed area in the first superconducting electrode pattern. Then, the first superconducting electrode material with the same thickness as the etching depth is deposited by magnetron sputtering. Subsequently, it is immersed in acetone solution at 60°C for 3 min. The first superconducting electrode material and the first photoresist layer 6 covering the first photoresist layer 6 are removed by a stripping process to form a patterned electrode structure. Then, the oxide layer generated on the electrode surface is removed to obtain the embedded first superconducting electrode layer 2. The parameters of the reactive ion etching include: the etching gas is CF4 gas, the etching power is 100W, the etching time is 5.5 min, and the etching depth is 60 nm. The parameters of the magnetron sputtering method include: the target material is high-purity niobium superconducting material, and the vacuum degree is 5×10 -8 The sputtering power was 200W, the deposition gas pressure was 2mTorr, and the target distance was 6cm.

[0080] The product illustration after step (2) is shown below. Figure 3 As shown.

[0081] (3) Using an optical microscope, select a two-dimensional topological semimetal single crystal material sheet (size 10×10μm) with tilted Weyl cones. 2 The two-dimensional topological semi-metallic single crystal material sheet (with a thickness of 5 nm) is positioned and transferred to a predetermined region on the silicon substrate 1 and the first superconducting electrode layer 2 to form a barrier layer 3.

[0082] The product illustration after step (3) is shown below. Figure 4 As shown.

[0083] (4) Based on step (3), an aluminum film with a thickness of 1 nm is deposited in a vacuum chamber as a metal protective layer 4 by electron beam evaporation, and then a second superconducting electrode layer 5 with a thickness of 120 nm is deposited by magnetron sputtering.

[0084] The parameters of the magnetron sputtering method include: the target material is high-purity niobium superconducting material, and the vacuum degree is 5×10⁻⁶. - 8 Torr, sputtering power of 100W, deposition gas pressure of 5mTorr, target distance of 10cm.

[0085] The product illustration after step (4) is shown below. Figure 5 As shown.

[0086] (5) A second photoresist layer 7 is spin-coated and deposited on the second superconducting electrode layer 5, and then photolithography is performed to define the junction region of the Josephson junction and the pattern of the second superconducting electrode; the material of the second photoresist layer 7 is AZ1500.

[0087] The product illustration after step (5) is shown below. Figure 6 As shown.

[0088] (6) SF6 gas is used for reactive ion etching for 150s to remove the junction region of the Josephson junction and the second superconducting electrode material outside the second superconducting electrode pattern. Then, the semi-finished product is placed in acetone solution at 60°C to remove the second photoresist layer 7. Then, it is immersed in AZ 300MIF alkaline solution (AZ1500 developer) for 3s to quickly remove the metal protective layer 4 outside the junction region of the Josephson junction and the second superconducting electrode pattern. Finally, it is rinsed with alcohol and dried with nitrogen to obtain the Josephson junction.

[0089] The product illustration after step (6) is shown below. Figure 7 As shown.

[0090] The DC and AC Josephson effects of the Josephson junction provided in Example 1 were characterized, and the characterization results are as follows: Figure 8-10 As shown. Among them, Figure 8 The resistance-temperature curve of the Josephson junction provided in Example 1 during the cooling process is shown. As can be seen from the figure, its resistance gradually decreases with decreasing temperature over a wide temperature scale, showing a decreasing trend of metallic characteristics. Furthermore, as the temperature decreases further, the resistance of the device gradually approaches zero at a temperature of approximately 7.8K. Figure 9 The current-voltage characteristic curve of the Josephson junction provided in Example 1 at T = 3.2K is shown. A robust Josephson current Ic ≈ 70μA can be observed from the figure. Figure 10 The voltage-current characteristic curves of the Josephson junction provided in Example 1 under microwave irradiation are shown. The Shapiro step induced by the AC Josephson effect can be observed from the figure, indicating that the device has a wide AC Josephson response from 15.8 GHz to 360 GHz.

[0091] Example 2 This embodiment provides a Josephson node, the Josephson node comprising: A silicon-based substrate, wherein the silicon-based substrate is a Si / SiO2 substrate.

[0092] A first superconducting electrode layer is embedded in the silicon substrate, and the upper surface of the first superconducting electrode layer is exposed from the silicon substrate.

[0093] A barrier layer comprising a two-dimensional topological single-crystal material having an inclined Weyl cone; the barrier layer is disposed on the silicon substrate and is in direct contact with a portion of the upper surface of the first superconducting electrode layer.

[0094] A metal protective layer is disposed on the silicon substrate and extends to the barrier layer, covering a portion of the upper surface of the barrier layer.

[0095] The second superconducting electrode layer is disposed on the metal protective layer and is electrically connected to the barrier layer through the metal protective layer.

[0096] Wherein, the two-dimensional topological single crystal material is NbIrTe4, and the AB plane crystal orientation of the two-dimensional topological single crystal material is parallel to the surface of the silicon substrate; the thickness of the barrier layer is 2nm, and is less than the sum of the coherence lengths of the first superconducting electrode and the second superconducting electrode; the width of the region in direct contact between the barrier layer and the upper surface of the first superconducting electrode layer is 1μm; the material of the metal protective layer is aluminum, and the thickness is 1nm; the superconducting material of the first superconducting electrode layer is niobium, and the thickness is 30nm; the superconducting material of the second superconducting electrode layer is niobium, and the thickness is 150nm; the vertical projection of the electrical connection region between the second superconducting electrode layer and the barrier layer on the silicon substrate does not overlap with the first superconducting electrode layer, and the width of the vertical projection is 50nm.

[0097] This embodiment also provides a method for preparing the above-mentioned Josephson knot, the method comprising the following steps: (1) Provide a silicon substrate and use acetone, alcohol and deionized water in sequence to ultrasonically clean the surface of the silicon substrate to remove organic contaminants, particles and other surface impurities; the silicon substrate is a Si / SiO2 substrate.

[0098] A first photoresist layer is spin-coated onto the cleaned silicon substrate surface, and then the first photoresist layer is subjected to ultraviolet lithography and developed to form a first superconducting electrode pattern; the material of the first photoresist layer is LOR10B+AZ1500.

[0099] (2) Reactive ion etching is performed on the silicon substrate in the exposed area of ​​the first superconducting electrode pattern. Then, a first superconducting electrode material with the same thickness as the etching depth is deposited by magnetron sputtering. Subsequently, it is immersed in an acetone solution at 60°C for 3 minutes to remove the first superconducting electrode material and the first photoresist layer covering the first photoresist layer by a lift-off process, forming a patterned electrode structure. Then, the oxide layer generated on the electrode surface is removed to obtain the embedded first superconducting electrode layer. The parameters of the reactive ion etching include: the etching gas is CF4 gas, the etching power is 100W, the etching time is 3 minutes, and the etching depth is 30nm. The parameters of the magnetron sputtering method include: the target material is high-purity niobium superconducting material, and the vacuum degree is 5×10 -8 The sputtering power was 180W, the deposition gas pressure was 1.8mTorr, and the target distance was 6cm.

[0100] (3) Using an optical microscope, select a two-dimensional topological semimetal single crystal material sheet (size 2×2μm) with tilted Weyl cones. 2The two-dimensional topological semi-metallic single crystal material sheet (with a thickness of 2 nm) is positioned and transferred to a predetermined region on the silicon substrate and the first superconducting electrode layer to form a barrier layer.

[0101] (4) Based on step (3), an aluminum film with a thickness of 1 nm is deposited in a vacuum chamber as a metal protective layer by electron beam evaporation, and then a second superconducting electrode layer with a thickness of 100 nm is deposited by magnetron sputtering.

[0102] The parameters of the magnetron sputtering method include: the target material is high-purity niobium superconducting material, and the vacuum degree is 5×10⁻⁶. - 8 The sputtering power was 80W, the deposition gas pressure was 5mTorr, and the target distance was 10cm.

[0103] (5) A second photoresist layer is spin-coated and deposited on the second superconducting electrode layer, and then photolithography is performed to define the junction region of the Josephson junction and the pattern of the second superconducting electrode; the material of the second photoresist layer is AZ1500.

[0104] (6) SF6 gas is used for reactive ion etching for 120s to remove the junction region of the Josephson junction and the second superconducting electrode material other than the second superconducting electrode pattern. Then, the semi-finished product is placed in acetone solution at 60°C to remove the second photoresist layer. Then, it is immersed in alkaline solution with a concentration of AZ 300MIF for 3s to quickly remove the metal protective layer of the junction region of the Josephson junction and the second superconducting electrode pattern. Finally, it is rinsed with alcohol and dried with nitrogen to obtain the Josephson junction.

[0105] Example 3 This embodiment provides a Josephson node, the Josephson node comprising: A silicon-based substrate, wherein the silicon-based substrate is a Si / SiO2 substrate.

[0106] A first superconducting electrode layer is embedded in the silicon substrate, and the upper surface of the first superconducting electrode layer is exposed from the silicon substrate.

[0107] A barrier layer comprising a two-dimensional topological single-crystal material having an inclined Weyl cone; the barrier layer is disposed on the silicon substrate and is in direct contact with a portion of the upper surface of the first superconducting electrode layer.

[0108] A metal protective layer is disposed on the silicon substrate and extends to the barrier layer, covering a portion of the upper surface of the barrier layer.

[0109] The second superconducting electrode layer is disposed on the metal protective layer and is electrically connected to the barrier layer through the metal protective layer.

[0110] Wherein, the two-dimensional topological single crystal material is NbIrTe4, and the AB plane of the two-dimensional topological single crystal material is parallel to the surface of the silicon substrate; the thickness of the barrier layer is 15 nm, and is less than the sum of the coherence lengths of the first superconducting electrode and the second superconducting electrode; the width of the region in direct contact between the barrier layer and the upper surface of the first superconducting electrode layer is 30 μm; the material of the metal protective layer is aluminum, and the thickness is 2 nm; the superconducting material of the first superconducting electrode layer is niobium, and the thickness is 70 nm; the superconducting material of the second superconducting electrode layer is niobium, and the thickness is 150 nm; the vertical projection of the electrical connection region between the second superconducting electrode layer and the barrier layer on the silicon substrate does not overlap with the first superconducting electrode layer, and the width of the vertical projection is 20 μm.

[0111] This embodiment also provides a method for preparing the above-mentioned Josephson knot, the method comprising the following steps: (1) Provide a silicon substrate and use acetone, alcohol and deionized water in sequence to ultrasonically clean the surface of the silicon substrate to remove organic contaminants, particles and other surface impurities; the silicon substrate is a Si / SiO2 substrate.

[0112] A first photoresist layer is spin-coated onto the cleaned silicon substrate surface, and then the first photoresist layer is subjected to ultraviolet lithography and developed to form a first superconducting electrode pattern; the material of the first photoresist layer is LOR10B+AZ1500.

[0113] (2) Reactive ion etching is performed on the silicon substrate in the exposed area of ​​the first superconducting electrode pattern. Then, a first superconducting electrode material with the same thickness as the etching depth is deposited by magnetron sputtering. Subsequently, it is immersed in an acetone solution at 60°C for 3 minutes to remove the first superconducting electrode material and the first photoresist layer covering the first photoresist layer by a lift-off process, forming a patterned electrode structure. Then, the oxide layer generated on the electrode surface is removed to obtain the embedded first superconducting electrode layer. The parameters of the reactive ion etching include: the etching gas is CF4 gas, the etching power is 120W, the etching time is 7 minutes, and the etching depth is 80nm. The parameters of the magnetron sputtering method include: the target material is high-purity niobium superconducting material, and the vacuum degree is 5×10 -8 The sputtering power was 220W, the deposition gas pressure was 3mTorr, and the target distance was 6cm.

[0114] (3) Using an optical microscope, select a two-dimensional topological semimetal single crystal material sheet (size 50×50μm) with tilted Weyl cones. 2 The two-dimensional topological semi-metallic single crystal material sheet (with a thickness of 20 nm) is positioned and transferred to a predetermined region on the silicon substrate and the first superconducting electrode layer to form a barrier layer.

[0115] (4) Based on step (3), a 2nm thick aluminum film is deposited in the vacuum chamber as a metal protective layer by electron beam evaporation, and then a second superconducting electrode layer with a thickness of 150nm is deposited by magnetron sputtering.

[0116] The parameters of the magnetron sputtering method include: the target material is high-purity niobium superconducting material, and the vacuum degree is 5×10⁻⁶. - 8 The sputtering power was 120W, the deposition gas pressure was 8mTorr, and the target distance was 10cm.

[0117] (5) A second photoresist layer is spin-coated and deposited on the second superconducting electrode layer, and then photolithography is performed to define the junction region of the Josephson junction and the pattern of the second superconducting electrode; the material of the second photoresist layer is AZ1500.

[0118] (6) SF6 gas is used for reactive ion etching for 160s to remove the junction region of the Josephson junction and the second superconducting electrode material outside the second superconducting electrode pattern. Then, the semi-finished product is placed in acetone solution at 60°C to remove the second photoresist layer, and then immersed in AZ 300MIF alkaline solution for 3s to quickly remove the metal protective layer outside the junction region of the Josephson junction and the second superconducting electrode pattern. Finally, it is rinsed with alcohol and dried with nitrogen to obtain the Josephson junction.

[0119] Example 4 The difference between this embodiment and Embodiment 1 is that the thickness of the barrier layer is greater than the sum of the coherence lengths of the first superconducting electrode and the second superconducting electrode.

[0120] The remaining preparation methods and parameters are consistent with those in Example 1.

[0121] Example 5 The difference between this embodiment and Embodiment 1 is that the thickness of the metal protective layer is 5 nm.

[0122] The remaining preparation methods and parameters are consistent with those in Example 1.

[0123] Comparative Example 1 The difference between this comparative example and Example 1 is that the barrier layer is replaced with a tantalum oxide layer.

[0124] The remaining preparation methods and parameters are consistent with those in Example 1.

[0125] Comparative Example 2 The difference between this comparative example and Example 1 is that no metal protective layer is provided.

[0126] The remaining preparation methods and parameters are consistent with those in Example 1.

[0127] analyze: In summary, this invention introduces a two-dimensional topological semi-metallic single crystal material with tilted Weyl cones as a barrier layer into the Josephson junction. Simultaneously, a metal protective layer is introduced to separate the second superconducting electrode layer and the barrier layer, achieving a highly transparent interface contact between the superconducting electrode and the barrier layer, significantly reducing contact resistance. The Josephson junction exhibits a wide-bandwidth AC Josephsonson response of 15.8-360 GHz. Furthermore, the strong nonlinear optical response imparted by the tilted Weyl cones in the barrier layer allows the Josephson junction to exhibit significantly enhanced photoelectric detection under terahertz irradiation. The effective coupling between the topological surface states induced by the tilted Weyl cones in the barrier layer and the superconducting paired states achieves synergistic enhancement of topological and superconducting properties. Moreover, the fabrication process provided by this invention is highly compatible with existing micro / nano fabrication technologies, fundamentally avoiding conflicts inherent in two-dimensional topological semi-metallic single crystals during micro / nano fabrication processes. This improves the structural stability of the barrier layer in subsequent processes, removes a major technical obstacle to large-scale mass production, and provides a novel and promising technical route for the industrialization of high-performance terahertz detectors.

[0128] As can be seen from the comparison between Example 1 and Example 4, if the thickness of the barrier layer is too large, there is no Josephson effect between the two superconducting electrodes, but rather geometric capacitive coupling.

[0129] A comparison between Example 1 and Example 5 shows that if the thickness of the metal protective layer is too large, it will affect the characteristics of the barrier itself.

[0130] As can be seen from the comparison between Example 1 and Comparative Example 1, if the tantalum oxide layer is used as the barrier layer, the interface is prone to defects due to lattice mismatch and atomic diffusion, which affects the device performance.

[0131] As can be seen from the comparison between Example 1 and Comparative Example 2, if no metal protective layer is provided, the two-dimensional single crystal surface is easily damaged during the subsequent growth of electrode materials, thus destroying the integrity of the interface barrier.

[0132] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A Josephson knot, characterized in that, The Josephson node includes: Substrate; A first superconducting electrode layer is embedded in the substrate, and the upper surface of the first superconducting electrode layer is exposed from the substrate; A barrier layer comprising a two-dimensional topological single-crystal material having an inclined Weyl cone; the barrier layer is disposed on the substrate and is in direct contact with a portion of the upper surface of the first superconducting electrode layer; A metal protective layer is disposed on the substrate and extends to the barrier layer, covering at least a portion of the upper surface of the barrier layer; The second superconducting electrode layer is disposed on the metal protective layer and is electrically connected to the barrier layer through the metal protective layer.

2. The Josephson knot according to claim 1, characterized in that, The two-dimensional topological single crystal material includes any one of NbIrTe4, TaIrTe4, or WTe2; And / or, the AB plane of the two-dimensional topological single crystal material is parallel to the surface of the substrate; And / or, the thickness of the barrier layer is less than the sum of the coherence lengths of the first superconducting electrode and the second superconducting electrode.

3. The Josephson knot according to claim 1 or 2, characterized in that, The material of the metal protective layer includes aluminum or titanium; And / or, the thickness of the metal protective layer is 1-2 nm.

4. The Josephson knot according to any one of claims 1-3, characterized in that, The substrate is a silicon-based substrate; And / or, the superconducting material of the first superconducting electrode layer includes any one of niobium, niobium nitride, or niobium titanium nitride; And / or, the thickness of the first superconducting electrode layer is 30-80 nm; And / or, the superconducting material of the second superconducting electrode layer includes any one of niobium, niobium nitride, or niobium titanium nitride; And / or, the thickness of the second superconducting electrode layer is 100-150 nm; And / or, the vertical projection of the electrical connection region between the second superconducting electrode layer and the barrier layer on the substrate does not overlap with the first superconducting electrode layer, and the width of the vertical projection is 80nm-30μm.

5. A method for preparing a Josephson knot as described in any one of claims 1-4, characterized in that, The preparation method includes: A substrate is provided in which an embedded first superconducting electrode layer is formed, such that the upper surface of the first superconducting electrode layer is exposed from the substrate; A two-dimensional topological single crystal material with an inclined Weyl cone is transferred to a predetermined region on the substrate and the first superconducting electrode layer to form a barrier layer; A metal protective layer and a second superconducting electrode layer are sequentially deposited on the substrate and the barrier layer; The metal protective layer and the second superconducting electrode layer are selectively etched to remove portions of the second superconducting electrode layer and the metal protective layer outside a predetermined region, thereby obtaining the Josephson junction.

6. The preparation method according to claim 5, characterized in that, The method for forming the embedded first superconducting electrode layer includes: A first photoresist layer is deposited on a substrate, and the first photoresist layer is subjected to ultraviolet lithography to form a first superconducting electrode pattern. The substrate in the exposed area of ​​the first superconducting electrode pattern is etched to deposit the first superconducting electrode material. The first superconducting electrode material and the first photoresist layer covering the first photoresist layer are removed by a stripping process to obtain the embedded first superconducting electrode layer.

7. The preparation method according to claim 5 or 6, characterized in that, The deposition method for the metal protective layer includes electron beam evaporation or molecular beam epitaxy.

8. The preparation method according to any one of claims 5-7, characterized in that, The selective etching method includes: A second photoresist layer is deposited on the upper surface of the second superconducting electrode layer, and the junction region of the Josephson junction and the pattern of the second superconducting electrode are formed by photolithography; reactive ion etching is performed to remove the second superconducting electrode material other than the junction region of the Josephson junction and the pattern of the second superconducting electrode. Remove the second photoresist layer, and then etch away the junction region of the Josephson junction and the metal protective layer outside the second superconducting electrode pattern.

9. The preparation method according to any one of claims 5-8, characterized in that, The preparation method includes: A silicon substrate is provided, a first photoresist layer is spin-coated and deposited on the silicon substrate, and the first photoresist layer is subjected to ultraviolet lithography to form a first superconducting electrode pattern; Reactive ion etching is performed on the silicon substrate in the exposed area of ​​the first superconducting electrode pattern. A first superconducting electrode material with the same thickness as the etching depth is deposited by magnetron sputtering. The first superconducting electrode material and the first photoresist layer covering the first photoresist layer are removed by a lift-off process to form a patterned electrode structure. The oxide layer generated on the electrode surface is removed to obtain the embedded first superconducting electrode layer. A two-dimensional topological single crystal material with an inclined Weyl cone is provided, and the two-dimensional topological single crystal material is positioned and transferred to a predetermined region on the substrate and the first superconducting electrode layer to form a barrier layer; A metal protective layer is deposited on the silicon substrate and the barrier layer by electron beam evaporation, and a second superconducting electrode layer is deposited by magnetron sputtering. A second photoresist layer is spin-coated and deposited on the second superconducting electrode layer, and the junction region of the Josephson junction and the pattern of the second superconducting electrode are formed by photolithography; reactive ion etching is performed to remove the second superconducting electrode material other than the junction region of the Josephson junction and the pattern of the second superconducting electrode. The second photoresist layer is removed, and then the junction region of the Josephson junction and the metal protective layer outside the second superconducting electrode pattern are removed by dry etching or wet etching to obtain the Josephson junction.

10. A superconducting device, characterized in that, The superconducting device includes the Josephson junction as described in any one of claims 1-4, or the Josephson junction prepared by the method described in claims 5-9.

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