Method for inducing high-temperature superconductive Josephson junction by using laser heat effect

Abstract

The invention discloses a method for inducing a high-temperature superconducting Josephson junction by using a laser heat effect, which belongs to the technical field of micro-nano processing, and comprises the following steps of: sequentially preparing a high-temperature superconducting material layer and a protective layer on the surface of a substrate, gluing and photoetching on the surface of the protective layer to obtain a high-temperature superconducting Josephson junction; the method comprises the following steps of: obtaining a junction region coated with photoresist and an electrode region coated with photoresist, removing a protective layer and a high-temperature superconducting material layer outside the junction region and the electrode region, removing the photoresist in the junction region and the electrode region, drying, and carrying out approximation crossing type radiation on the high-temperature superconducting material layer and the protective layer in the junction region through laser spots, and the high-temperature superconductive Josephson junction is prepared. According to the method, the high-temperature superconductor is radiated by adopting the nano-sized laser spot, and through radiation of the laser spot, precise control over the nano-sized heat effect of the high-temperature superconductor is effectively achieved, so that a potential barrier is formed, the high-temperature superconductive Josephson junction is obtained, precise control over the nano-sized heat effect of the high-temperature superconductor is achieved, and the high-temperature superconductive Josephson junction is obtained. And the high-temperature superconductive Josephson junction of which the potential barrier is formed by local modification is successfully prepared. According to the process, the manufacturing process is simplified, the production cost is reduced, meanwhile, the performance stability of the prepared device is ensured, and the effect of integrated development of the high-temperature superconducting Josephson junction and the superconducting quantum device is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-nano processing, and in particular relates to a method for inducing a high-temperature superconducting Josephson junction by utilizing laser thermal effect. Background Art

[0002] In the field of superconducting quantum devices, there are many methods for preparing high-temperature superconducting Josephson junctions, each of which has certain disadvantages. The twin crystal junction requires a twin crystal substrate, which is expensive and the position of the junction cannot be arbitrarily selected; the quality of the step junction depends on the microstructure of the step, and the repeatability is poor; the electron transport and noise performance of the step SNS junction is not ideal; the electron transport and noise performance of the nanowire junction is very easy to deteriorate; the electron transport performance of the focused He ion beam irradiation junction is very unstable. According to patent CN115148891A, a method for preparing a high-temperature superconducting Josephson junction is provided. The high-temperature superconducting Josephson junction prepared by the method has the problem of being too expensive. These disadvantages largely limit the practical application of the high-temperature superconducting Josephson junction in the field of superconducting quantum devices. Therefore, in order to overcome the above disadvantages and promote the application of high-temperature superconducting Josephson junctions, new requirements for low cost, high flexibility, strong repeatability, ideal and stable performance, and efficient preparation are required for the new preparation method. At present, there is a lack of a preparation method that meets the new requirements for high-temperature superconducting Josephson junctions. Summary of the invention

[0003] The present invention proposes a method for inducing a high-temperature superconducting Josephson junction using laser thermal effect, so as to solve the problems of high cost, poor flexibility, difficulty in repeatability, substandard performance, instability, etc. of the existing preparation method. Through the method of the present invention, a high-temperature superconducting Josephson junction can be prepared on a single crystal substrate, thereby greatly reducing the production cost, simplifying the complexity of the process, and enabling large-scale and efficient preparation.

[0004] A method for inducing a high-temperature superconducting Josephson junction by utilizing laser thermal effect comprises the following steps: sequentially preparing a high-temperature superconducting material layer and a protective layer on the surface of a substrate, coating the surface of the protective layer with glue and performing photolithography to obtain a junction region coated with photoresist and an electrode region coated with photoresist, removing the protective layer and the high-temperature superconducting material layer outside the junction region and the electrode region, removing the photoresist in the junction region and the electrode region, drying, and performing near-through radiation on the high-temperature superconducting material layer and the protective layer in the junction region by means of a laser spot to prepare a high-temperature superconducting Josephson junction.

[0005] The wavelength of the laser spot is 405 nm, the diameter is 275 μm, the laser power is 210-240 mW, the pulse time is 100 ns, and the delay between points is 5 ms.

[0006] A high-temperature superconducting material layer is prepared on the substrate by a pulsed laser deposition method, and a protective layer is prepared on the high-temperature superconducting material layer by a magnetron sputtering deposition method.

[0007] The substrate is an aluminum oxide substrate, the high-temperature superconducting material layer is a YBCO film, and the protective layer is an Au film.

[0008] The thickness of the YBCO film is 100 nm, and the thickness of the Au film is 30 nm.

[0009] The junction region has a length of 15 μm and a width of 3 μm.

[0010] When the thickness of the YBCO film varies, the laser power needs to be adjusted for irradiation. For example, a 220mW laser can etch YBCO with a thickness of 100nm, but cannot etch YBCO with a thickness of 200nm, so the power needs to be increased. In other words, YBCO films of different thicknesses require different laser powers to be etched.

[0011] The purpose of setting the three parameters of laser power, pulse time and point delay is to be able to etch YBCO. For example: if the power of 210mW is not enough to etch YBCO, the power needs to be increased until YBCO can be etched; if the junction area is over-etched after etching with a power of 231mW and a pulse time of 300ns, but YBCO cannot be etched with a power of 230mW and a pulse time of 100ns, it is necessary to use a power of 230mW and a pulse time of 200ns to etch to achieve the right etching effect.

[0012] The protection layer and the high temperature superconducting material layer outside the junction region and the electrode region are removed by ion beam etching.

[0013] Compared with the prior art, the present invention has the following advantages and technical effects:

[0014] The present invention uses a nanometer-sized laser spot to irradiate a high-temperature superconductor. Through the radiation of the laser spot, the high-temperature superconductor's nanoscale thermal effect is effectively controlled to form a potential barrier, thereby obtaining a high-temperature superconducting Josephson junction. This technology simplifies the manufacturing process, reduces production costs, and ensures the performance stability of the prepared device, achieving the effect of integrated development of a high-temperature superconducting Josephson junction and a superconducting quantum device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] Figure 1 The process flow chart of preparing a high temperature superconducting Josephson junction in Example 1;

[0017] Figure 2 A schematic diagram of two parallel line segments in a canvas designed by the Photoshop software of the present invention;

[0018] Figure 3 It is a schematic diagram of importing the canvas designed by Photoshop software into the thin film microbridge in the present invention;

[0019] Figure 4 This is a scanning electron microscope (SEM) image of a gap of 205 nm obtained after laser irradiation in Example 1;

[0020] Figure 5 This is a SEM image of a gap with a spacing of 187 nm obtained after laser irradiation in Example 2;

[0021] Figure 6 This is a SEM image of a gap with a spacing of 177 nm obtained after laser irradiation in Example 3;

[0022] Figure 7 From left to right in the figure are the current-voltage (IV) characteristic curves of the high-temperature superconducting Josephson junctions prepared in Example 1, Example 2 and Example 3;

[0023] Figure 8 From left to right in the figure are the V-Φ curves of the superconducting quantum interference devices prepared in Example 1, Example 2 and Example 3. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0026] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0027] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0028] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0029] The embodiment of the present invention provides a method for inducing a high-temperature superconducting Josephson junction using a laser thermal effect, comprising the following steps: providing a substrate, preparing a layer of high-temperature superconducting material film and a protective layer on the surface of the substrate; coating and photolithography the surface of the protective layer above the high-temperature superconducting material layer to obtain a junction area coated with photoresist and an electrode area coated with photoresist, etching the area outside the junction area and the electrode area, after etching, the protective layer and the high-temperature superconducting material layer outside the junction area and the electrode area should completely disappear; using acetone and anhydrous ethanol to ultrasonically degas and clean the product to remove the photoresist in the junction area and the electrode area, and drying; using a nano-sized laser spot to perform approximate through-radiation on the protective layer material and the high-temperature superconducting material in the junction area, forming a potential barrier in the area after the laser spot is radiated, and obtaining a high-temperature superconducting Josephson junction. Optionally, by selecting different laser parameters, high-temperature superconducting material film thickness, junction area width, etc., a high-temperature superconducting Josephson junction with different performance parameters can be achieved.

[0030] The approximate through-radiation in the present invention specifically refers to: designing a 2000*2000 pixel canvas in Photoshop software in advance, and then designing two line segments with a length of 18 pixels on the canvas, the two line segments are parallel and on the same straight line, and the interval is 1 pixel, such as Figure 2 As shown, Figure 2 The two black lines in the figure are the two line segments mentioned above. These two line segments are the two lines that will be etched after being passed to the laser lithography machine. Export the canvas to a common image format (such as png format), and then import it into the laser lithography machine program. The laser lithography machine will recognize the pattern and transfer it to the microbridge of the film by irradiation. Two parallel line segments with a length of 1.8μm and located on the same straight line will be displayed on the microbridge, with a spacing of 0.1μm between them (1 pixel on the image corresponds to 0.1μm on the etched pattern). Figure 3 As shown, the gray area is the bottom substrate, the black area is the YBCO and Au microbridge, and the red line segment represents the path of the laser scanning. Since there are two paths, there is a 0.1μm gap between the two paths. In other words, this 0.1μm gap is formed by the approximation of the two paths. At the same time, the two paths pass through the microbridge, so it is called approximate through-radiation.

[0031] Pulsed laser deposition (PLD), also known as pulsed laser ablation, is a physical vapor deposition technology used to deposit thin films onto substrates under vacuum. The basic principle of pulsed laser deposition is to bombard a target material with a high energy density and short pulse time laser. Under the action of the laser, the surface of the target material quickly absorbs the laser energy and heats up, causing the target material to evaporate into plasma. These plasmas continue to bombard the substrate surface under the action of the laser, and eventually deposit on the substrate to form a thin film. The pulsed laser deposition process is usually divided into three stages: melting and evaporation of the target material: the laser is focused on the target material, causing it to quickly heat up and evaporate into plasma; plasma transmission: the evaporated plasma is transmitted in space and is affected by various physical phenomena (such as collisions, thermal excitation, etc.); thin film deposition: after the plasma reaches the substrate, it condenses on the substrate surface and forms a thin film.

[0032] The laser used in the pulsed laser deposition method used in the embodiment of the present invention is a KrF excimer laser (wavelength 248nm), and the laser energy density is 1-3J / cm 2 , the pulse repetition frequency is 1-10Hz. The deposition substrate temperature is 780-820℃, the background oxygen pressure is 200-300mTorr, the distance between the target and the substrate is 4-6cm, and after the film deposition is completed, the cooling rate is controlled under high oxygen pressure, the cooling rate is 5-10℃ / min, and then annealing is performed in a high oxygen atmosphere.

[0033] The magnetron sputtering deposition method is a process in which argon gas is ionized by applying voltage in a high vacuum environment, and the movement of electrons is controlled by a magnetic field, so that the electrons move in a spiral shape near the target surface, thereby increasing the probability of electrons hitting the argon gas to produce ions. These ions are accelerated to bombard the target surface under the action of the electric field, so that the target atoms or molecules are sputtered out and deposited on the substrate to form a thin film. The specific parameters of the magnetron sputtering method for preparing niobium superconducting thin films in the embodiment of the present invention are: the target power range is 100W-300W, the argon pressure range is 2-5mTorr, the substrate temperature range is 50-200℃, and then annealing treatment is performed, the annealing temperature range is 150-250℃, and the annealing time is 30-60min.

[0034] UV lithography refers to the technology of using ultraviolet light source to selectively expose photoresist in space, and then transfer the designed pattern to the wafer. It has the characteristics of large area, easy operation, mass production and low cost.

[0035] Development is a key step in the UV lithography process. It refers to the process of selectively retaining the exposed area (negative photoresist) or the unexposed area (positive photoresist) in a specific chemical solution by taking advantage of the difference in chemical properties between the exposed area and the unexposed area, thereby obtaining the final desired photoresist structure. The general development operation process is to take out the photolithography sample and immediately pour it into the pre-warmed developer.

[0036] Ion beam etching (IBE), also known as ion milling, is an advanced micro-nano manufacturing technology. The principle of ion beam etching is to use a high-energy ion beam to impact the surface of a solid target material to achieve layer-by-layer removal of the material. In this process, energy is transferred from the incident ions to the atoms on the solid surface. When the binding energy between atoms on the solid surface is lower than the energy of the incident ions, the atoms on the solid surface will be moved away or removed from the surface. The energy of the ion beam etching in the embodiment of the present invention is 300eV, the beam current is 60mA, and the total net etching time is 70min.

[0037] Example 1

[0038] S1. A YBCO film with a thickness of 100 nm was deposited on an alumina substrate using pulsed laser deposition (PLD). The specific parameters of the pulsed laser deposition method were: laser energy density of 2 J / cm 2, the pulse repetition frequency is 10Hz. The deposition substrate temperature was 800°C, the background oxygen pressure was 300mTorr, and the distance between the target and the substrate was 5cm. After the film deposition was completed, the cooling rate was controlled under high oxygen pressure, and the cooling rate was 5°C / min. Then, annealing was performed in a high oxygen atmosphere (600°C, 60min) to prepare a YBCO film. The obtained YBCO film was cleaned by oxygen plasma to remove pollutants and oxides on its surface. Then, the YBCO surface was treated by argon plasma to increase its surface chemical reactivity. Finally, a 30nm thick Au film was deposited on the YBCO film in situ by magnetron sputtering to protect the YBCO film from the influence of air. During the deposition process, argon (Ar) was used as the working gas. The argon molecules were accelerated to collide with the gold target, sputtering the atoms on the gold target onto the surface of the YBCO film. The target power was 200W, the argon pressure was 5mTorr, and the substrate temperature was 100°C. Then, annealing was performed at 200°C and the annealing time was 60min.

[0039] S2. Spin-coat a layer of AR-P 3700 photoresist on the Au film prepared in S1, with the speed of the photoresist spreader at 10,000 rpm and the running time at 1 min to ensure that the photoresist is as uniform and thin as possible. Then place the product on a heating plate and bake it for 90 seconds to ensure that the solvent is fully evaporated. Place the mask of the primary structure pattern in the appropriate position of the photolithography machine (this operation is only required once), expose the above photoresist for 10 seconds by ultraviolet photolithography, and develop it for 30 seconds to obtain a photoresist structure comprising a junction area with a length of 15 μm and a width of 3 μm and an electrode area of ​​2000 μm×2000 μm. Subsequently, the junction and electrode area patterns are transferred to the Au and YBCO films by ion beam etching (IBE), and the etching of the areas outside the junction and electrode areas is completed so that the Au layer and YBCO layer outside the junction and electrode areas should completely disappear. The energy of ion beam etching is 300 eV, the beam current is 60 mA, and the total net etching time is 70 min.

[0040] S3. The product obtained in S2 is placed in acetone and anhydrous ethanol successively, and ultrasonic degassing and cleaning is performed in an ultrasonic cleaning machine for 3 minutes respectively to remove the photoresist above the Au film and the YBCO film junction area and the electrode area, and then the product is dried at 100°C for 20 seconds.

[0041] S4. Use laser equipment to process the junction area of ​​Au and YBCO at nanoscale. The wavelength of the laser spot is 405nm and the diameter is 275μm. The Au and YBCO materials in the junction area are irradiated in a near-through manner. The laser parameters are selected as follows: power is 220mW, pulse time is 100ns, and the delay between points is 5ms. A high-temperature superconducting Josephson junction is prepared. After irradiation with this power laser, a gap with a spacing of 205nm can be obtained, such as Figure 4 shown.

[0042] Figure 1 This is a process flow chart for preparing a high-temperature superconducting Josephson junction in this embodiment.

[0043] Example 2

[0044] S1-S3 are the same as in Example 1

[0045] S4. Use laser equipment to process the junction area of ​​Au and YBCO at nanoscale. The wavelength of the laser spot is 405nm and the diameter is 275μm. The Au and YBCO materials in the junction area are irradiated in a near-through manner. The laser parameters are: power of 225mW, pulse time of 100ns, and delay between points of 5ms. A high-temperature superconducting Josephson junction is prepared. After high-power laser irradiation, a gap of 187nm can be obtained. Figure 5 shown.

[0046] Example 3

[0047] S1-S3 are the same as in Example 1

[0048] S4. Use laser equipment to process the junction area of ​​Au and YBCO at nanoscale. The wavelength of the laser spot is 405nm and the diameter is 275μm. The Au and YBCO materials in the junction area are irradiated in a near-through manner. The laser parameters are selected as follows: power is 230mW, pulse time is 100ns, and the delay between points is 5ms. A high-temperature superconducting Josephson junction is prepared. After irradiation with this power laser, a gap with a spacing of 177nm can be obtained, such as Figure 6 shown.

[0049] It can be seen from Examples 1-3 that the gap distance can be precisely controlled by adjusting the laser radiation parameters, which proves that the present invention uses a nanometer-sized laser spot to irradiate the high-temperature superconductor, and through the radiation of the laser spot, it effectively realizes the precise control of the nanoscale thermal effect of the high-temperature superconductor to form a potential barrier, and successfully prepares a high-temperature superconducting Josephson junction with local modification to form a potential barrier.

[0050] Comparative Example 1

[0051] The same as Example 1, except that the thickness of the YBCO film in S1 is 120 nm, and the specific operation is as follows:

[0052] S1. A YBCO film with a thickness of 120 nm was deposited on an alumina substrate using pulsed laser deposition (PLD). The specific parameters of the pulsed laser deposition method were: laser energy density of 3 J / cm 2 , the pulse repetition frequency is 10Hz. The deposition substrate temperature was 800°C, the background oxygen pressure was 300mTorr, and the distance between the target and the substrate was 5cm. After the film deposition was completed, the cooling rate was controlled under high oxygen pressure, and the cooling rate was 5°C / min. Then, annealing was performed in a high oxygen atmosphere (600°C, 60min) to prepare a YBCO film. The obtained YBCO film was cleaned by oxygen plasma to remove pollutants and oxides on its surface. Then, the YBCO surface was treated by argon plasma to increase its surface chemical reactivity. Finally, a 30nm thick Au film was deposited on the YBCO film in situ by magnetron sputtering to protect the YBCO film from the influence of air. During the deposition process, argon (Ar) was used as the working gas. The argon molecules were accelerated to collide with the gold target, sputtering the atoms on the gold target onto the surface of the YBCO film. The target power was 200W, the argon pressure was 5mTorr, and the substrate temperature was 100°C. Then, annealing was performed at 200°C and the annealing time was 60min.

[0053] Comparative Example 2

[0054] The same as Example 1, except that the thickness of the YBCO film in S1 is 80 nm, and the specific operation is as follows:

[0055] S1. A YBCO film with a thickness of 80 nm was deposited on an alumina substrate using pulsed laser deposition (PLD). The specific parameters of the pulsed laser deposition method were: laser energy density of 2 J / cm 2, the pulse repetition frequency is 5Hz. The deposition substrate temperature was 800°C, the background oxygen pressure was 300mTorr, and the distance between the target and the substrate was 5cm. After the film deposition was completed, the cooling rate was controlled under high oxygen pressure, and the cooling rate was 5°C / min. Then, annealing was performed in a high oxygen atmosphere (600°C, 60min) to prepare a YBCO film. The obtained YBCO film was cleaned by oxygen plasma to remove pollutants and oxides on its surface. Then, the YBCO surface was treated by argon plasma to increase its surface chemical reactivity. Finally, a 30nm thick Au film was deposited on the YBCO film in situ by magnetron sputtering to protect the YBCO film from the influence of air. During the deposition process, argon (Ar) was used as the working gas. The argon molecules were accelerated to collide with the gold target, sputtering the atoms on the gold target onto the surface of the YBCO film. The target power was 200W, the argon pressure was 5mTorr, and the substrate temperature was 100°C. Then, annealing was performed at 200°C and the annealing time was 60min.

[0056] Comparative Example 3

[0057] The same as Example 1, except that the laser parameters in S4 are selected as follows: power is 210 mW, pulse time is 100 ns, and inter-point delay is 5 ms, and a high-temperature superconducting Josephson junction is prepared.

[0058] Comparative Example 4

[0059] The same as Example 1, except that the laser parameters in S4 are selected as follows: power is 240 mW, pulse time is 100 ns, and inter-point delay is 5 ms, and a high-temperature superconducting Josephson junction is prepared.

[0060] Performance Test 1: Current-Voltage (IV) Characteristic Curve Measurement:

[0061] By applying currents of different intensities to a high-temperature superconducting Josephson junction and measuring the corresponding voltage response, its IV characteristic curve can be obtained.

[0062] The present invention measures the current-voltage (IV) characteristic curve of the high-temperature superconducting Josephson junctions prepared in Examples 1-3 and Comparative Examples 1-4 by a four-lead method, and the measurement results are as follows:

[0063] Figure 7 From left to right are the current-voltage (IV) characteristic curves of the high-temperature superconducting Josephson junctions prepared in Example 1, Example 2 and Example 3, from Figure 7 It can be seen that with the increase of laser power, the critical current I cIt gradually becomes smaller, and when the laser power is 220mW, it has a larger critical current of about 310μA. A higher critical current usually means that the Josephson junction can withstand a larger current without losing its superconducting properties, and has better stability and anti-interference ability.

[0064] In comparative example 1, the thickness of the YBCO film used was 120nm, and the laser power was 220mW. At this time, the laser power was insufficient to etch away the YBCO, and a Josephson junction could not be formed. In comparative example 2, the thickness of the YBCO film used was 80nm, and the laser power was 220mW. At this time, the laser power was too large, and the etching paths of the two original line segments were connected to form a long line segment, and the microbridge was disconnected, and a Josephson junction could not be formed.

[0065] In comparative example 3, the thickness of the YBCO film used was 100 nm, and the laser power was 210 mW. At this time, the laser power was insufficient to etch away the YBCO, and a Josephson junction could not be formed. In comparative example 4, the thickness of the YBCO film used was 100 nm, and the laser power was 240 mW. At this time, the laser power was too large, and the etching paths of the two original line segments were connected to form a long line segment, and the microbridge was disconnected, and a Josephson junction could not be formed.

[0066] Performance Test 2: Magnetic Flux Quantization Measurement

[0067] The superconducting quantum interference device formed by two Josephson junctions has the characteristic of magnetic flux quantization, that is, its internal magnetic flux is quantized. By measuring the magnetic flux quantization behavior of the superconducting quantum interference device, its performance stability can be evaluated and the voltage-flux (V-Φ) curve can be determined. Specific steps:

[0068] 1. Install the prepared nano superconducting quantum magnetometer in the fixture under the sample delivery rod, and the sample delivery rod is connected to two Keithley 2450 source meters;

[0069] 2. Slowly place the sample delivery rod in a low temperature environment (≤4K) and wait for the temperature to stabilize;

[0070] 3. Use the first Keithley 2450 source meter to provide the modulation current I mod ;

[0071] 4. Use the second Keithley 2450 source meter to provide bias current I b , the bias current should be slightly larger than the critical current I c , and simultaneously measure the voltage across the device;

[0072] 5. The automatic test software in the host computer sets the parameters of the two source meters and records the changes in voltage under different input magnetic fluxes, and analyzes the voltage-flux curve.

[0073] The magnetic flux quantization of the high temperature superconducting Josephson junctions prepared in Examples 1-3 and Comparative Examples 1-4 was measured by the above-mentioned measurement method, and the measurement results were as follows:

[0074] Figure 8 From left to right in the figure are the V-Φ curves of the superconducting quantum interference devices prepared in Example 1, Example 2 and Example 3, respectively. Figure 8 It can be seen that when the laser power is 220mW, the V pp Roughly 8μV, 225mw V pp About 7.5μV, V at 230mW pp It is roughly 7μV. The slope of the curve in the V-Φ curve represents the sensitivity of the superconducting quantum interference device. When the laser power is 220mw, the sensitivity is higher, so the optimal working parameter of the laser power is 220mw.

[0075] Comparative Examples 1, 2, 3 and 4 all failed to prepare Josephson junctions, and thus this item test could not be performed.

[0076] Performance test three: long-term stability test:

[0077] The high-temperature superconducting Josephson junction is placed under constant environmental conditions and its performance parameters (such as critical current density, IV characteristics, etc.) are monitored for a long time. By observing the changes in performance parameters over time, the long-term stability of the Josephson junction can be evaluated.

[0078] The present invention uses the four-lead method and the above-mentioned V-Φ test method to conduct a long-term stability test on the high-temperature superconducting Josephson junctions prepared in Examples 1-3 and Comparative Examples 1-4. The test results are: the test data after 7 days is almost the same as the initial test data, which proves that the high-temperature superconducting Josephson junction prepared by the present invention has strong long-term stability.

[0079] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for inducing a high-temperature superconducting Josephson junction using laser thermal effect, characterized in that: The method comprises the following steps: sequentially preparing a high-temperature superconducting material layer and a protective layer on the surface of a substrate, coating the protective layer with glue and performing photolithography to obtain a junction region coated with photoresist and an electrode region coated with photoresist, removing the protective layer and the high-temperature superconducting material layer outside the junction region and the electrode region, removing the photoresist in the junction region and the electrode region, drying, and performing near-through radiation on the high-temperature superconducting material layer and the protective layer in the junction region through a laser spot to prepare a high-temperature superconducting Josephson junction.

2. The method of inducing a high temperature superconducting Josephson junction using laser thermal effect according to claim 1, characterized in that: The wavelength of the laser spot is 405 nm, the diameter is 275 μm, the laser power is 220-230 mW, the pulse time is 100 ns, and the delay between points is 5 ms.

3. The method of inducing a high temperature superconducting Josephson junction using laser thermal effect according to claim 1, characterized in that: A high-temperature superconducting material layer is prepared on the substrate by a pulsed laser deposition method, and a protective layer is prepared on the high-temperature superconducting material layer by a magnetron sputtering deposition method.

4. The method of inducing high temperature superconducting Josephson junction by laser thermal effect according to claim 3, characterized in that: The substrate is an aluminum oxide substrate, the high-temperature superconducting material layer is a YBCO film, and the protective layer is an Au film.

5. The method of inducing high temperature superconducting Josephson junction by using laser thermal effect according to claim 4, characterized in that: The thickness of the YBCO film is 100 nm, and the thickness of the Au film is 30 nm.

6. The method of inducing high temperature superconducting Josephson junction by utilizing laser thermal effect according to claim 4, characterized in that: The junction region has a length of 15 μm and a width of 3 μm.

7. The method of inducing high temperature superconducting Josephson junction by utilizing laser thermal effect according to claim 1, characterized in that: The protection layer and the high temperature superconducting material layer outside the junction region and the electrode region are removed by ion beam etching.

Images