Method for realizing low-temperature preparation of Nb3Sn film through high-power pulse magnetron sputtering and application of substrate bias
By combining high-power pulsed magnetron sputtering with substrate bias, Nb3Sn thin films were prepared at low temperatures, solving the problem of superconducting performance degradation in existing technologies and realizing the preparation of high-performance Nb3Sn thin films suitable for Cu-based SRF cavities.
Patent Information
- Application Number
- CN202511694650.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-18
- Publication Date
- 2026-02-13
AI Technical Summary
Existing technologies cannot prepare pure-phase Nb3Sn films with excellent superconducting properties at temperatures below 800°C, leading to a deterioration in the superconducting performance of Cu-based SRF cavities.
Nb3Sn thin films were prepared at low temperatures using high-power pulsed magnetron sputtering and substrate bias. By combining a specific range of substrate bias with high-power pulsed magnetron sputtering technology, the energy of sputtered particles was increased to promote the deposition and crystallization of Nb3Sn thin films.
High-quality Nb3Sn thin films were prepared at 400℃ with a superconducting transition temperature exceeding 17K. This avoided the volatilization of Sn during annealing, reduced impurity formation, and improved superconducting performance.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a method for realizing low-temperature preparation of Nb3Sn thin film. BACKGROUND
[0002] Currently, the core component of particle accelerators, superconducting radio frequency (SRF) cavities, are mostly made of high-purity niobium (Nb). However, after decades of development, the performance of Nb cavities has approached its theoretical limit, making it difficult to meet the performance requirements of higher accelerating gradients and quality factors in the future. Therefore, the prior art has been seeking alternative materials to Nb. Among the many candidates, Nb3Sn of A15 structure shows great potential, with a superconducting transition temperature (~18.3K) and a thermodynamic critical magnetic field (~400mT) higher than that of niobium, which can theoretically further improve the accelerating gradient and quality factor of SRF cavities.
[0003] However, the inherent brittleness and poor thermal conductivity of bulk Nb3Sn material make it impossible to be directly processed into a cavity. A practical technical path is to deposit a few microns thick Nb3Sn superconducting thin film on the inner surface of the existing cavity material. Currently, this thin film is mainly prepared by reacting niobium cavities with tin vapor at a high temperature of more than 1100℃ (i.e. tin vapor phase diffusion method). This high-temperature process is completely suitable for the niobium cavity itself, but it severely limits the choice of substrate materials.
[0004] In fact, copper (Cu) as a substrate material for SRF cavities has double advantages that niobium cannot match:
[0005] 1. Excellent thermal stability: At the working temperature of 4.2K liquid helium of superconducting cavities, the thermal conductivity of copper is more than twenty times that of niobium. This means that the Cu-based superconducting cavity can quickly conduct the tiny heat generated locally (such as magnetic flux vortex dissipation caused by defects) to the liquid helium pool, effectively avoiding the quenching of the superconducting state caused by the "thermal instability" phenomenon, greatly improving the running robustness of the cavity.
[0006] 2. Significant economy: On the one hand, the material cost of high-purity copper is much lower than that of high-purity niobium; on the other hand, due to the excellent thermal conductivity of copper, the heat conduction efficiency is higher, which can greatly reduce the long-term operation and maintenance cost of SRF cavities.
[0007] Although Cu-based cavities have a broad prospect and are considered as the ideal choice for the next generation of SRF cavities, there is a fundamental technical barrier in depositing a key superconducting material Nb3Sn film on the inner surface thereof: the temperature required for high-quality crystallization of Nb3Sn (> 1100℃) far exceeds the tolerance temperature of the Cu-based body (< 800℃). Once the processing temperature exceeds 800℃, the copper cavity will be deformed or fail in performance. Therefore, how to prepare a pure-phase Nb3Sn film with excellent superconducting performance at a "safe temperature" below 800℃ has become a technical bottleneck restricting the development of the next generation of high-performance and low-cost SRF cavities. The existing technology usually obtains a superconducting film rich in Sn islands and impurities such as Nb6Sn5 and NbSn2 in this low-temperature range, resulting in a sharp deterioration of superconducting performance. SUMMARY
[0008] The present application solves the problem that the prior art cannot prepare a pure-phase Nb3Sn film with excellent superconducting performance at a temperature below 800℃, and further provides a method for low-temperature preparation of an Nb3Sn film by high-power pulsed magnetron sputtering and application of a substrate bias.
[0009] A method for low-temperature preparation of an Nb3Sn film by high-power pulsed magnetron sputtering and application of a substrate bias, which is carried out according to the following steps:
[0010] I. Substrate preparation and pretreatment:
[0011] Fix the film-coated test piece to be plated on the sample table in the vacuum chamber, and then perform vacuum pumping on the vacuum chamber;
[0012] II. Low-temperature heating and atmosphere control:
[0013] Start the heating system to heat the film-coated test piece to be plated to the deposition temperature, then introduce the sputtering working gas into the vacuum chamber, and adjust the gas pressure in the vacuum chamber to be at the sputtering working pressure;
[0014] III. Bias-assisted high-power pulsed magnetron sputtering:
[0015] Use an Nb3Sn alloy target as the sputtering source, turn on the high-power pulsed magnetron sputtering power supply and the substrate bias power supply, and perform sputter deposition at the bias and deposition temperature;
[0016] IV. In-situ cooling and sampling:
[0017] After sputter deposition, sequentially turn off the substrate bias power supply, the high-power pulsed magnetron sputtering power supply and the heating system, and naturally cool to room temperature in a vacuum environment, and take out the deposited test piece, thereby completing a method for low-temperature preparation of an Nb3Sn film by high-power pulsed magnetron sputtering and application of a substrate bias.
[0018] The present application has the following advantages:
[0019] 1. The regulation strategy of HiPIMS combined with substrate bias: the method of using high power pulsed magnetron sputtering combined with a specific range of substrate bias to improve the energy of sputtering particles, which can improve the superconducting performance of Nb3Sn thin film on the one hand, and maintain the Sn content in the film at a suitable interval on the other hand. The interaction of HiPIMS combined with bias on the improvement of particle energy realizes the low-temperature synthesis of high-quality Nb3Sn thin film.
[0020] 2. Low-temperature in-situ preparation: depositing Nb3Sn thin film on a heated test piece to be plated, sputtering in a short time, and the thin film can complete good crystallization without producing other impurities. Compared with the prior art, this step reduces the subsequent long annealing process. In addition, through this way, the deterioration of superconducting performance caused by the volatilization of Sn element in the annealing process can be effectively avoided.
[0021] 3. Low-temperature process compatible with Cu substrate: based on the regulation strategy of HiPIMS combined with substrate bias, superconducting Nb3Sn thin film is prepared at a deposition temperature of 400℃; and high-performance superconducting thin film is prepared at 750℃, with a superconducting transition temperature of more than 17K.
[0022] The present application completes the deposition process of the thin film at low temperature by the synergistic effect of HiPIMS and a specific substrate bias. The present application can reduce the preparation temperature of Nb3Sn thin film to 400℃ and has superconducting performance. The prepared thin film has a superconducting transition temperature of more than 17K and more excellent superconducting performance when the test piece to be plated is heated to 750℃. This preparation method can be extended to the inner surface of the Cu-based cavity to realize one-step direct preparation of high-performance superconducting thin film. BRIEF DESCRIPTION OF DRAWINGS
[0023] Figure 1 XRD pattern of Nb3Sn superconducting thin film prepared at 400℃ in Example 1;
[0024] Figure 2 XRD pattern of Nb3Sn superconducting thin film prepared at 750℃ in Example 2;
[0025] Figure 3 Resistance-temperature curve of Nb3Sn superconducting thin film prepared at 400℃ in Example 1;
[0026] Figure 4 SEM pattern and resistance-temperature curve of Nb3Sn superconducting thin film prepared at 750℃ in Example 2, (a) is the SEM pattern of the surface morphology of the thin film, (b) is the SEM pattern of the cross-sectional morphology of the thin film, and (c) is the resistance-temperature curve of the thin film. DETAILED DESCRIPTION
[0027] Specific embodiment one: the embodiment is a method for low-temperature preparation of Nb3Sn thin film by high-power pulsed magnetron sputtering and substrate bias, which is carried out according to the following steps:
[0028] I. Substrate preparation and pretreatment:
[0029] Fix the film-coated test piece on the sample table in the vacuum chamber, and then vacuumize the vacuum chamber;
[0030] II. Low-temperature heating and atmosphere control:
[0031] Start the heating system, heat the film-coated test piece to the deposition temperature, then introduce the sputtering working gas into the vacuum chamber, and adjust the gas pressure in the vacuum chamber to the sputtering working pressure;
[0032] III. Bias-assisted high-power pulsed magnetron sputtering:
[0033] Use the Nb3Sn alloy target as the sputtering source, turn on the high-power pulsed magnetron sputtering power supply and the substrate bias power supply, and perform sputtering deposition at the bias and deposition temperature;
[0034] IV. In-situ cooling and sampling:
[0035] After sputtering deposition, sequentially turn off the substrate bias power supply, high-power pulsed magnetron sputtering power supply and heating system, and naturally cool to room temperature in a vacuum environment, then take out the deposited test piece, which completes a method for low-temperature preparation of Nb3Sn thin film by high-power pulsed magnetron sputtering and substrate bias.
[0036] The specific embodiment faces the sharp contradiction between high phase formation temperature and low tolerance temperature, and can overcome the two irreconcilable contradictions by high-power pulsed magnetron sputtering technology combined with substrate bias, to prepare high-performance Nb3Sn thin film at a lower temperature. Through research, it is found that high-power pulsed magnetron sputtering technology combined with substrate bias can maximize the advantages of particle energy on superconducting performance and weaken its disadvantages. The combination of the two technologies can significantly enhance the sputtering particle energy, promote its migration and diffusion on the substrate surface, and thus effectively inhibit the generation of impurity phases. And in this process, it will not cause the decline of the film performance. At the lowest substrate temperature of 400℃, Nb3Sn thin film with superconducting performance is prepared, and the entire process does not require any subsequent heat treatment or annealing process.
[0037] The beneficial effects of the embodiment are:
[0038] 1. The regulation strategy of HiPIMS combined with substrate bias: The method of using high-power pulsed magnetron sputtering combined with a specific range of substrate bias to improve the energy of sputtering particles. This method can improve the superconducting performance of Nb3Sn thin film on the one hand, and maintain the Sn content in the film within a suitable range on the other hand. The interaction of HiPIMS combined with bias on the improvement of particle energy realizes the low-temperature synthesis of high-quality Nb3Sn thin film.
[0039] 2. Low-temperature in-situ preparation: Depositing Nb3Sn thin film on a heated test piece to be plated, sputtering in a short time, the thin film can complete good crystallization without producing other impurities. Compared with the prior art, this step reduces the subsequent long annealing process. In addition, this method can effectively avoid the deterioration of superconducting performance caused by the volatilization of Sn element during the annealing process.
[0040] 3. Low-temperature process compatible with Cu substrate: Based on the regulation strategy of HiPIMS combined with substrate bias, superconducting Nb3Sn thin film is prepared at a deposition temperature of 400℃; and high-performance superconducting thin film is prepared at 750℃, with a superconducting transition temperature exceeding 17K.
[0041] The embodiment realizes the deposition process of the thin film at low temperature by the synergistic effect of HiPIMS and a specific substrate bias. The embodiment can reduce the preparation temperature of the Nb3Sn thin film to 400℃ and has superconducting performance. The prepared thin film has a superconducting transition temperature exceeding 17K and superior superconducting performance when the test piece to be plated is heated to 750℃. This preparation method can be extended to the inner surface of the Cu-based cavity to realize one-step direct preparation of high-performance superconducting thin film.
[0042] Specific implementation method two: The difference between this embodiment and specific implementation method one is that the test piece to be plated in step one is a cavity test piece or a sheet test piece. The others are the same as specific implementation method one.
[0043] Specific implementation method three: The difference between this embodiment and specific implementation method one or two is that the vacuum chamber is vacuumized in step one, and the background vacuum degree is less than 1×10 -3 Pa. The others are the same as specific implementation method one or two.
[0044] Specific implementation method four: The difference between this embodiment and one of specific implementation methods one to three is that the deposition temperature in step two is 400℃-750℃. The others are the same as specific implementation methods one to three.
[0045] Specific implementation method five: The difference between this embodiment and one of specific implementation methods one to four is that the sputtering working gas in step two is argon. The others are the same as specific implementation methods one to four.
[0046] Sixth embodiment: different from one of the first to fifth embodiments is that the sputtering working pressure in step two is 0.1 Pa to 1.0 Pa. The others are the same as the first to fifth embodiments.
[0047] Seventh embodiment: different from one of the first to sixth embodiments is that the setting parameters of the high-power pulsed magnetron sputtering power source in step three are as follows: the sputtering power is 200 W to 400 W, the pulse frequency is 50 Hz to 400 Hz, and the pulse width is 100 μs to 400 μs. The others are the same as the first to sixth embodiments.
[0048] Eighth embodiment: different from one of the first to seventh embodiments is that the bias voltage in step three is 0 V to -300 V. The others are the same as the first to seventh embodiments.
[0049] Ninth embodiment: different from one of the first to eighth embodiments is that the sputtering deposition in step three is carried out under the conditions of the sputtering working pressure being 0.1 Pa to 1.0 Pa, the bias voltage being 0 V to -300 V, the deposition temperature being 400 ℃ to 750 ℃, the sputtering power being 200 W to 400 W, the pulse frequency being 50 Hz to 400 Hz, and the pulse width being 100 μs to 400 μs. The others are the same as the first to eighth embodiments.
[0050] Tenth embodiment: different from one of the first to ninth embodiments is that the setting parameters of the high-power pulsed magnetron sputtering power source in step three are as follows: the sputtering power is 300 W, the pulse frequency is 200 Hz, and the pulse width is 300 μs; and the bias voltage in step three is -50 V. The others are the same as the first to ninth embodiments.
[0051] The beneficial effects of the present application are verified by the following examples:
[0052] Example one:
[0053] A method for realizing low-temperature preparation of Nb3Sn thin film by high-power pulsed magnetron sputtering and applying substrate bias voltage, which is carried out according to the following steps:
[0054] I. Substrate preparation and pretreatment:
[0055] Fix the film-plating sample to be plated on the sample table in the vacuum chamber, seal the cavity, and then start the mechanical pump and the molecular pump group to vacuumize the vacuum chamber, so that the background vacuum degree is 8.0×10 -4 Pa;
[0056] II. Low-temperature heating and atmosphere control:
[0057] Start the heating system, heat the sample to be plated to a deposition temperature of 400℃, then introduce the sputtering working gas into the vacuum chamber, and adjust the gas pressure in the vacuum chamber to 1.0 Pa;
[0058] The sputtering working gas is high-purity argon;
[0059] III. Bias-assisted high-power pulsed magnetron sputtering
[0060] Use a Nb3Sn alloy target as the sputtering source, turn on the high-power pulsed magnetron sputtering power supply and the substrate bias power supply, and under the conditions of a sputtering working pressure of 1.0 Pa, a bias voltage of -50 V, a deposition temperature of 400℃, a sputtering power of 300 W, a pulse frequency of 200 Hz, and a pulse width of 300μs, pre-sputter for 10 min, then open the target baffle, and sputter and deposit for 90 min;
[0061] IV. In-situ cooling and sampling
[0062] After sputter deposition, sequentially turn off the substrate bias power supply, the high-power pulsed magnetron sputtering power supply, and the heating system, and naturally cool to room temperature in a vacuum environment (about 4h-6h), take out the deposited sample, and obtain a layer of surface-dense, silver-gray Nb3Sn superconducting thin film on the sample.
[0063] The sample to be plated in step one is a 10mm×10mm×0.65mm sapphire substrate that has been cleaned and dried.
[0064] The stoichiometric ratio of the Nb3Sn alloy target in step three is Nb:Sn=3:1.
[0065] The thickness of the Nb3Sn superconducting thin film prepared in Example One is about 1µm.
[0066] Example Two: The difference between this example and Example One is that the deposition temperature in steps two and three is 750℃. The others are the same as in Example One.
[0067] The thickness of the Nb3Sn superconducting thin film prepared in Example Two is about 1µm.
[0068] Figure 1 The XRD pattern of the Nb3Sn superconducting thin film prepared at 400℃ in Example One; as can be seen from the figure, the Nb3Sn superconducting thin film basically does not contain any other impurities.
[0069] Figure 2 The XRD pattern of the Nb3Sn superconducting thin film prepared at 750℃ in Example Two; as can be seen from the figure, the Nb3Sn superconducting thin film basically does not contain any other impurities, and has a high degree of crystallization.
[0070] Figure 3The resistance-temperature curve of the Nb3Sn superconducting thin film prepared at 400℃ in Example 1; as can be seen from the figure, the thin film has superconducting performance, and the superconducting transition temperature is about 10K.
[0071] Figure 4 The SEM images and the resistance-temperature curve of the Nb3Sn superconducting thin film prepared at 750℃ in Example 2, (a) is the SEM image of the surface morphology of the thin film, (b) is the SEM image of the cross-sectional morphology of the thin film, and (c) is the resistance-temperature curve of the thin film; as can be seen from figure (a), there is no Sn island on the surface of the thin film, and the continuous undulating morphology on the surface of the thin film is caused by the growth of columnar crystals; figure (b) shows that the thin film is dense, and the thickness is about 1µm; figure (c) shows that the superconducting transition temperature is more than 17K.
[0072] Table 1 The ratio of the total number of atoms of niobium to the total number of atoms of tin in different regions of the Nb3Sn superconducting thin film prepared at 750℃ in Example 2
[0073]
Claims
1. A method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying a substrate bias voltage, characterized in that... It is done in the following steps: I. Substrate Preparation and Pretreatment: The specimen to be coated is fixed on the sample stage of the vacuum chamber, and then the vacuum chamber is evacuated. II. Low-Temperature Heating and Atmosphere Control: Start the heating system to heat the sample to be coated to the deposition temperature, then introduce sputtering working gas into the vacuum chamber and adjust the gas pressure in the vacuum chamber to the sputtering working gas pressure; III. Bias-assisted high-power pulsed magnetron sputtering: An Nb3Sn alloy target was used as the sputtering source. A high-power pulsed magnetron sputtering power supply and a substrate bias power supply were turned on, and sputtering deposition was performed at the bias and deposition temperature. IV. In-situ cooling and sampling: After sputtering deposition, the substrate bias power supply, the high-power pulsed magnetron sputtering power supply and the heating system are turned off in sequence, and the sample is naturally cooled to room temperature in a vacuum environment. The deposited sample is then taken out, thus completing a method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias.
2. The method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias voltage according to claim 1, characterized in that... The specimen to be coated in step one is a cavity specimen or a sheet specimen.
3. The method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias voltage according to claim 1, characterized in that... In step one, the vacuum chamber is evacuated to a background vacuum level below 1×10⁻⁶. -3 Pa.
4. The method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias voltage according to claim 1, characterized in that... The deposition temperature described in step two is 400℃~750℃.
5. The method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias voltage according to claim 1, characterized in that... The sputtering working gas mentioned in step two is argon.
6. The method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias voltage according to claim 1, characterized in that... The sputtering working pressure mentioned in step two is 0.1 Pa to 1.0 Pa.
7. The method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias voltage according to claim 1, characterized in that... The settings for the high-power pulsed magnetron sputtering power supply in step three are as follows: sputtering power of 200W~400W, pulse frequency of 50Hz~400Hz, and pulse width of 100μs~400μs.
8. The method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias voltage according to claim 1, characterized in that... The bias voltage mentioned in step three is 0V to -300V.
9. The method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias voltage according to claim 1, characterized in that... In step three, sputtering deposition is carried out under the following conditions: sputtering working pressure of 0.1 Pa to 1.0 Pa, bias voltage of 0 V to -300 V, deposition temperature of 400 °C to 750 °C, sputtering power of 200 W to 400 W, pulse frequency of 50 Hz to 400 Hz, and pulse width of 100 μs to 400 μs.
10. The method for low-temperature preparation of Nb3Sn thin films by high-power pulsed magnetron sputtering and applying substrate bias voltage according to claim 1, characterized in that... The settings for the high-power pulsed magnetron sputtering power supply in step three are as follows: sputtering power of 300W, pulse frequency of 200Hz, pulse width of 300μs; and bias voltage of -50V as mentioned in step three.