Oxygen annealing method of Fe (Se, Te) superconducting thin film

Abstract

The invention relates to an oxygen annealing method for a Fe (Se, Te) superconducting thin film, which comprises the following steps of: putting the Fe (Se, Te) thin film epitaxially grown by pulsed laser deposition (PLD) into an annealing cavity, opening a vacuum pump to vacuumize to be less than 1Pa, opening an oxygen valve, continuously introducing oxygen with a specific flow, heating the cavity to reach a specific annealing temperature, keeping the temperature for a specific annealing time, and cooling to the room temperature to obtain the Fe (Se, Te) superconducting thin film. And naturally cooling to the room temperature of 25 DEG C, and taking out the Fe (Se, Te) film. Compared with the prior art, the method has the advantages that the c-axis lattice constant of the annealed Fe (Se, Te) thin film is reduced, the critical transformation temperature Tc is increased, the critical current density Jc is increased, the Jc is increased to 19.60 MA / cm < 2 > under a self-field at 4.2 K after annealing in the oxygen flow of 210 SCCM, and the Jc is increased to 4.27 MA / cm < 2 > under a 9 T magnetic field. The oxygen annealing method is beneficial to removal of interstitial Fe atoms and promotes application of the Fe (Se, Te) thin film in a high-intensity magnetic field.

Description

Technical Field

[0001] The invention relates to the technical field of superconducting thin films, and in particular to an oxygen annealing method for a Fe(Se, Te) superconducting thin film. Background Art

[0002] The iron-based superconductors discovered in 2008 overturned the view that ferromagnetic long-range order and superconductivity cannot coexist, indicating that even macroscopic magnetism cannot suppress the appearance of Cooper pairs. However, in the growth process of iron-based superconductors, the introduction of excess interstitial Fe elements is inevitable. The non-stoichiometric Fe elements have led various research groups to draw contradictory conclusions about iron-based superconductors. Ferromagnetic interstitial Fe atoms occupy the Se / Te layer, and interact with the Fe layer to destroy Cooper pairs, localize carriers, and suppress superconductivity. The chemical valence of the interstitial Fe element is +1, which electron-dopes the superconducting material.

[0003] Patent CN202111645742.6 discloses a Fe(Se,Te) superconducting thick film and its preparation method and application. The preparation method of the Fe(Se,Te) superconducting thick film is: using a multi-channel pulsed laser deposition method, first depositing a Fe(Se,Te) seed layer on a metal substrate coated with a buffer layer, and then depositing multiple Fe(Se,Te) superconducting layers on the Fe(Se,Te) seed layer. Although this technology makes the critical temperature T c and critical current I c The Fe(Se,Te) superconducting film has higher temperature and better performance, but the interstitial Fe element is inevitably introduced during the cooling process, and the film with poor performance may have disadvantages such as uneven element distribution and low crystallinity.

[0004] Researcher Sun Yue found the optimal conditions after annealing Fe(Se,Te) single crystals with oxygen for different time and temperature, and found that the T c and J c The superconducting volume fraction increased, and the Meissner state of magnetic flux expulsion was imaged using magneto-optical imaging technology, and it was found that superconductivity evolved from the periphery to the center. 0.55 Te 0.45 After the single crystal was placed in an atmosphere of S and Te and heated to 300°C for annealing, it was found that T c and J c The superconducting volume fraction increases, and iron chalcogenides are formed on the surface of the single crystal. Yasuna Kawasaki FeTe 1-x Se xAfter the single crystal was sealed with oxygen and annealed at different temperatures and times, it was found that its a-axis and c-axis lattice constants had almost no change. The phase diagram was redrawn and it was found that the superconducting region of the sample expanded after annealing, that is, less Se content doping after annealing can make the bulk superconductivity appear.

[0005] In the application process, the presence of interstitial Fe elements suppresses superconductivity, localizes carriers, and increases the J c The removal of interstitial Fe elements is beneficial to the high-field application of Fe(Se,Te) films.

[0006] Patent application CN202410063713.6 discloses a J c Weak magnetic field dependence of FeSexTe 1-x Superconducting polycrystalline block and preparation method thereof, firstly, the raw material ratio in the preparation of Fe(Se,Te) polycrystalline is adjusted so that pure β-phase Fe is formed after melting and sintering. 1+y (Se,Te) polycrystals. Then, the polycrystals are annealed at a specific temperature and time in a specific low-oxygen environment to remove the interstitial iron in the polycrystal bulk without affecting the phase purity, so that the polycrystals regain excellent superconducting properties and restore their intrinsic δT c Pinning, finally got J c Weak field-dependent Fe(Se,Te) superconducting polycrystalline bulk material. However, this technology is only applicable to polycrystalline bulk materials with multiple orientations and cannot be applied to two-dimensional thin film materials. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide an oxygen annealing method for Fe(Se,Te) superconducting thin films, which can remove interstitial Fe elements and increase the critical transition temperature T c and critical current density J c .

[0008] The object of the present invention can be achieved by the following technical solution: An oxygen annealing method for a Fe(Se,Te) superconducting film comprises the following steps:

[0009] (1) Place the Fe(Se,Te) film in an annealing chamber and evacuate the chamber;

[0010] (2) continuously introducing a specific flow rate of oxygen into the annealing chamber;

[0011] (3) heating to a specific annealing temperature and maintaining the temperature for a specific annealing time;

[0012] (4) Cool naturally to room temperature; thus, the annealed Fe(Se,Te) film is obtained.

[0013] Furthermore, the Fe(Se,Te) film in step (1) is formed on a substrate coated with CeO 2 The buffer layer is epitaxially grown on Hastelloy C276 using pulsed laser deposition (PLD).

[0014] Furthermore, in step (1), the vacuum is evacuated to below 1 Pa, and during the subsequent annealing process, the vacuum pump is always kept open to allow oxygen to flow.

[0015] Furthermore, in step (2), the oxygen flow rate is 28 SCCM to 561 SCCM.

[0016] Furthermore, in step (2), the oxygen flow rate is 28 SCCM, 144 SCCM, 210 SCCM, and 561 SCCM.

[0017] Furthermore, in step (3), the annealing temperature is 100° C. and the annealing time is 30 min to 4 h.

[0018] Furthermore, the annealing time is 30 min, 2 h, and 4 h.

[0019] Furthermore, in step (3), the heating rate is 2-3°C / min.

[0020] Furthermore, in step (3), the heating rate is 2.5°C / min.

[0021] Furthermore, the thickness of the Fe(Se,Te) film in step (1) is 100-200 nm.

[0022] Furthermore, the c-axis lattice constant of the Fe(Se,Te) film in step (1) is greater than

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention performs post-annealing treatment on the Fe(Se,Te) film in oxygen. The c-axis lattice constant of the Fe(Se,Te) film after annealing is reduced. Different oxygen flow rates and different annealing times make the T of the Fe(Se,Te) superconducting film c and J c There are different degrees of improvement. After annealing in an oxygen flow rate of 210 SCCM at 4.2K, the J c Increased to 19.60MA / cm 2 , J under 9T magnetic field c Increased to 4.27MA / cm 2 Slightly higher annealing temperature may cause the film to quench. c The increase in shows that oxygen annealing increases the superconducting volume fraction and may remove the interstitial Fe element.

[0025] 2. The thickness of the Fe(Se,Te) single crystal film of the present invention is controlled at 100-200nm. After post-annealing in oxygen, the single crystal has better superconducting properties than polycrystalline bulk materials. There are many differences between the two-dimensional superconductivity of the film and the three-dimensional superconductivity of the bulk material. The two-dimensional superconductivity exhibits more exotic physical properties, such as the dependence of the superconductivity on the film thickness. Compared with the bulk material, the superconducting phase of the film is more stable, T c and J c Furthermore, the present application performs post-annealing in pure oxygen, eliminating the influence of inert gas, and the flow rate of oxygen can also be regulated to achieve a better annealing result.

[0026] 3. The present invention adopts a method of coating CeO 2 The Fe(Se,Te) superconducting film was prepared by using pulsed laser deposition (PLD) epitaxial growth method on Hastelloy C276 as buffer layer, and the critical temperature of PLD growth was increased by annealing treatment under specific environment and conditions. c and critical current I c The synergistic effect of the two makes the distribution of each element more uniform and the crystallinity higher, which promotes the strong magnetic field application of Fe(Se,Te) film. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the oxygen annealing device of the Fe(Se,Te) superconducting film in the present invention;

[0028] Figure 2 XRD diffraction patterns of the unannealed Fe(Se,Te) superconducting films of the present invention and Examples 1-3;

[0029] Figure 3 RT diagrams of the unannealed Fe(Se,Te) superconducting films of the present invention and Examples 1-3;

[0030] Figure 4 It is a curve diagram of the critical current density of the Fe(Se,Te) superconducting film without annealing and in Examples 1-3 of the present invention as a function of the magnetic field;

[0031] Figure 5 RT diagrams of the unannealed Fe(Se,Te) superconducting films of the present invention and Examples 4 and 5;

[0032] Figure 6 The graph is a graph showing the change of critical current density of the Fe(Se,Te) superconducting film without annealing in the present invention and in Examples 4 and 5 with the magnetic field.

[0033] Figure 7XRD diffraction patterns of the unannealed Fe(Se,Te) superconducting films of the present invention and comparative examples 1-2;

[0034] Figure 8 RT diagram of the unannealed Fe(Se,Te) superconducting film in the present invention and in Comparative Example 1-2;

[0035] Fig. 9 It is a curve diagram of the critical current density of the Fe(Se,Te) superconducting film without annealing in the present invention and in comparative example 1 as a function of the magnetic field;

[0036] Fig.10 XRD diffraction patterns of the unannealed Fe(Se,Te) superconducting thin films of the present invention and comparative example 3;

[0037] Fig.11 RT diagram of the unannealed Fe(Se,Te) superconducting film in the present invention and in comparative example 3;

[0038] Fig.12 It is a curve diagram of the critical current density of the Fe(Se,Te) superconducting film without annealing in the present invention and in comparative example 3 as a function of the magnetic field;

[0039] Fig.13 XRD diffraction patterns of the unannealed Fe(Se,Te) superconducting thin films of the present invention and comparative example 4;

[0040] Fig.14 RT diagram of the unannealed Fe(Se,Te) superconducting film in the present invention and in comparative example 4. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments. The English technical terms mentioned in the present invention are all common knowledge in the field.

[0042] The invention provides a method for oxygen annealing of a Fe(Se, Te) superconducting film. The method comprises the following steps: placing the Fe(Se, Te) film in a G-CVD, evacuating the film to a vacuum level below 1 Pa, introducing oxygen at a specific flow rate, and heating the film for annealing.

[0043] Among them, Fe(Se,Te) film is formed on a substrate coated with CeO 2 The buffer layer is epitaxially grown on Hastelloy C276 using pulsed laser deposition (PLD), and the c-axis lattice constant is The length and width are 10cm×1cm.

[0044] The growth steps of the Fe(Se,Te) thin films used in the following Examples 1-3 and Comparative Examples 1-3 are as follows:

[0045] 1) Place the Fe(Se,Te) target in the target holder of the multi-channel pulsed laser deposition chamber, wind one end of the metal substrate coated with the buffer layer and the oxide barrier layer onto the reel, then pull the metal substrate to wind it around the rollers of the multi-channel transmission device multiple times to form a three-channel base tape between the rollers, and finally wind the other end onto another reel. The metal substrate is installed and its movement speed is adjusted by the encoder and the stepper motor. The distance between the base tape and the target is 4 cm. Close the chamber door and evacuate the chamber to 3.3×10 -7 Torr, turn on the argon mass flow meter connected to the chamber and set the flow rate of the gas flow to 10 SCCM;

[0046] 2) Start the baseband heating system to reach a heating temperature of 580°C;

[0047] 3) Start the target motion system and the excimer laser, adjust the laser energy to 250mJ and the laser repetition frequency to 40Hz;

[0048] 4) After the heating temperature, laser energy, and laser repetition frequency are stabilized at the above set values, the laser optical path switch is turned on to pre-sputter the Fe(Se,Te) superconducting target for 5 minutes;

[0049] 5) starting the baseband motion system, setting the motion speed of the metal substrate to 6 m / h, and causing the Fe(Se,Te) seed layer to grow epitaxially on the metal substrate;

[0050] 6) After the growth of the Fe(Se,Te) seed layer is completed, the stepper motor is turned off, the substrate movement is stopped, the heating temperature is changed to 450°C, the laser repetition frequency is changed to 80Hz, and the laser energy is still 250mJ;

[0051] 7) After the above parameters are stable, turn on the stepper motor, move the tape in the opposite direction to start growing the Fe(Se,Te) superconducting layer, and repeat this process three times;

[0052] 8) Turn off the stepper motor, change the movement speed of the metal substrate to 12m / h, change the heating temperature to 400℃, the laser repetition frequency remains at 80Hz, the laser energy remains at 250mJ, and after the parameters are stable, turn on the stepper motor to move the tape once;

[0053] 9) Turn off the stepper motor, change the movement speed of the metal substrate to 6m / h, change the heating temperature to 430℃, the laser repetition frequency remains at 80Hz, the laser energy remains at 250mJ, and after the parameters are stable, turn on the stepper motor to move the tape three times;

[0054] 10) After the epitaxial growth of the Fe(Se,Te) superconducting layer is completed, the baseband motion system, heating system, and laser optical path are turned off. When the heating system is cooled down to below 100°C, the target motion system and argon flow meter are turned off. The vacuum system is turned off, and the chamber door is opened to remove the Fe(Se,Te) superconducting film.

[0055] The differences between the preparation methods of Examples 4-5 are as follows: argon gas is not introduced; the laser energy in the whole process is 230 mJ; in step 1), the distance between the base tape and the target is 4.5 cm; in step 6), the heating temperature is 480°C; in step 8), the movement speed of the base tape is 6 m / h, the heating temperature is 300°C, and the laser repetition frequency is 40 Hz; in step 9), the base tape temperature is 400°C, and the tape is walked four times.

[0056] The differences of the preparation method of Comparative Example 4 are as follows: the flow rate of argon gas is 30 SCCM; the laser energy of the whole process is 180 mJ; the heating temperature in step 6) is 480°C, and the tape is walked twice; the superconducting layer growth is completed, there are no steps 8) and 9), and step 10) is executed.

[0057] Equipment for oxygen annealing of Fe(Se,Te) superconducting thin films such as Figure 1 As shown, it includes an oxygen cylinder 1, a mass flow meter 2, an annealing furnace 3, a bellows 4, and a vacuum pump 5 connected in sequence. The annealing furnace 3 is provided with a heating system 6. The annealing method specifically includes the following steps:

[0058] (1) Open the injection valve, place the Fe(Se,Te) film 7 into the annealing chamber of the annealing furnace 3, close the valve, turn on the vacuum pump 5 to evacuate the chamber, and use the vacuum pump 5 to make the vacuum degree of the annealing chamber reach below 1 Pa.

[0059] (2) Open the oxygen valve of the oxygen cylinder 1 and the mass flowmeter 2 to introduce a specific flow of oxygen; the preferred oxygen flow rate is 28 SCCM to 561 SCCM, and the more preferred oxygen flow rates are 28 SCCM, 144 SCCM, 210 SCCM, and 561 SCCM.

[0060] (3) Turn on the heating system 6 of the annealing furnace 3, raise the temperature to a specific annealing temperature, and keep the temperature for a specific annealing time; preferably, the heating rate is 2 to 3°C / min, the annealing temperature is 100°C, and the annealing time is 30min to 4h, and more preferably, the heating rate is 2.5°C / min, the annealing temperature is 100°C, and the specific annealing time is 30min, 2h, or 4h.

[0061] (4) Turn off the heating system 6 and cool naturally to room temperature 25°C;

[0062] (5) Close the oxygen valve and mass flow meter 2, turn off the vacuum pump 5, and take out the annealed Fe(Se,Te) film.

[0063] Embodiment 1:

[0064] This embodiment provides an oxygen annealing method for a Fe(Se,Te) superconducting thin film, comprising the following steps:

[0065] (1) Open the injection valve, place the Fe(Se,Te) film into the annealing chamber, close the valve, and turn on the vacuum pump to evacuate to below 1 Pa;

[0066] (2) Open the oxygen valve and mass flow meter to continuously introduce 28 SCCM of oxygen;

[0067] (3) Turn on the heating system, set it to heat from room temperature 25°C to 100°C in 30 minutes, and then keep it warm for 2 hours;

[0068] (4) Turn off the heating system and cool naturally to room temperature of 25°C;

[0069] (5) Close the oxygen valve and mass flow meter, turn off the vacuum pump, and take out the annealed Fe(Se,Te) film.

[0070] like Figure 2 As shown in Figure 2, the c-axis lattice constant of the Fe(Se,Te) film after annealing in oxygen changes from Reduce to Increased crystallinity; e.g. Figure 3 As shown, When it is increased to 17.67K, the transition width decreases; Figure 4 As shown, at 4.2K, the J c Increased to 11.60MA / cm 2 , J under 9T magnetic field c Increased to 2.52MA / cm 2 .

[0071] Embodiment 2:

[0072] This embodiment provides an oxygen annealing method for a Fe(Se,Te) superconducting thin film, comprising the following steps:

[0073] (1) Open the injection valve, place the Fe(Se,Te) film into the annealing chamber, close the valve, and turn on the vacuum pump to evacuate to below 1 Pa;

[0074] (2) Open the oxygen valve and mass flow meter to continuously introduce 210 SCCM of oxygen;

[0075] (3) Turn on the heating system, set it to heat from room temperature 25°C to 100°C in 30 minutes, and then keep it warm for 2 hours;

[0076] (4) Turn off the heating system and cool naturally to room temperature of 25°C;

[0077] (5) Close the oxygen valve and mass flow meter, turn off the vacuum pump, and take out the annealed Fe(Se,Te) film.

[0078] like Figure 2 As shown, after annealing in oxygen, the c-axis lattice constant decreases to Increased crystallinity; e.g. Figure 3 As shown, compared with the unannealed Fe(Se,Te) film, after annealing in Example 2, When it is increased to 16.91K, the transition width decreases; Figure 4 As shown, at 4.2K, the J c Increased to 19.60MA / cm 2 , J under 9T magnetic field c Increased to 4.27MA / cm 2 .

[0079] Embodiment 3:

[0080] This embodiment provides an oxygen annealing method for a Fe(Se,Te) superconducting thin film, comprising the following steps:

[0081] (1) Open the injection valve, place the Fe(Se,Te) film into the annealing chamber, close the valve, and turn on the vacuum pump to evacuate to below 1 Pa;

[0082] (2) Open the oxygen valve and mass flow meter to continuously introduce 561 SCCM of oxygen;

[0083] (3) Turn on the heating system, set it to heat from room temperature 25°C to 100°C in 30 minutes, and then keep it warm for 2 hours;

[0084] (4) Turn off the heating system and cool naturally to room temperature of 25°C;

[0085] (5) Close the oxygen valve and mass flow meter, turn off the vacuum pump, and take out the annealed Fe(Se,Te) film.

[0086] like Figure 2 As shown in Figure 2, the c-axis lattice constant decreases less after annealing. Increased crystallinity; e.g. Figure 3 As shown, When it is increased to 17.45K, the transition width decreases; Figure 4 As shown, at 4.32K, the J c Increased to 15.33MA / cm 2 , J under 9T magnetic field c Increased to 3.04MA / cm 2 .

[0087] Embodiment 4:

[0088] This embodiment provides an oxygen annealing method for a Fe(Se,Te) superconducting thin film, comprising the following steps:

[0089] (1) Open the injection valve, place the Fe(Se,Te) film into the annealing chamber, close the valve, and turn on the vacuum pump to evacuate to below 1 Pa;

[0090] (2) Open the oxygen valve and mass flow meter to continuously introduce 144 SCCM of oxygen;

[0091] (3) Turn on the heating system, set it to heat from room temperature 25°C to 100°C in 30 minutes, and then keep it warm for 30 minutes;

[0092] (4) Turn off the heating system and cool naturally to room temperature of 25°C;

[0093] (5) Close the oxygen valve and mass flow meter, turn off the vacuum pump, and take out the annealed Fe(Se,Te) film.

[0094] like Figure 5 As shown, When it is increased to 17.49K, the transition width decreases; Figure 6 As shown, at 4.2K, the J c Increased to 18.25MA / cm 2 , J under 9T magnetic field c Increased to 3.20MA / cm 2 .

[0095] Embodiment 5:

[0096] This embodiment provides an oxygen annealing method for a Fe(Se,Te) superconducting thin film, comprising the following steps:

[0097] (1) Open the injection valve, place the Fe(Se,Te) film into the annealing chamber, close the valve, and turn on the vacuum pump to evacuate to below 1 Pa;

[0098] (2) Open the oxygen valve and mass flow meter to introduce a specific flow rate of 144 SCCM of oxygen;

[0099] (3) Turn on the heating system, set it to heat from room temperature 25°C to 100°C in 30 minutes, and then keep it warm for 4 hours;

[0100] (4) Turn off the heating system and cool naturally to room temperature of 25°C;

[0101] (5) Close the oxygen valve and mass flow meter, turn off the vacuum pump, and take out the annealed Fe(Se,Te) film.

[0102] like Figure 5 As shown, Increased to 17.64K; Figure 6 As shown, at 4.2K, the J c Increased to 14.72MA / cm 2 , J under 9T magnetic field c Increased to 2.72MA / cm 2 .

[0103] Comparative Example 1:

[0104] The difference between Comparative Example 1 and Example 1 is that the annealing temperature is 50° C., specifically, it takes 10 minutes to heat from room temperature 25° C. to 50° C., and then it is kept warm for 2 hours. The rest is the same as Example 1.

[0105] Depend on Figure 7 It can be seen that after annealing, the c-axis lattice constant decreases to The crystallinity is improved. Figure 8 It can be seen that T c onset rises to 17.23K, ΔTc decreases to 1.97K, Fig. 9 It can be seen that 4.2K from the field under J c Reduced to 7.92MA / cm 2 , J under 9T magnetic field c Reduced to 1.26MA / cm 2 .

[0106] Comparative Example 2:

[0107] The difference between Comparative Example 2 and Example 1 is that the annealing temperature is 150° C., specifically, it takes 50 minutes to heat from room temperature 25° C. to 150° C., and then it is kept warm for 2 hours. The rest is the same as Example 1.

[0108] Depend on Figure 7 It can be seen that after annealing, the c-axis lattice constant decreases to The crystallinity is improved. Figure 8 It can be seen that T c onset It drops to 11.98K, ΔT c It increases to 9.06K and the superconducting performance deteriorates.

[0109] Comparative Example 3:

[0110] This comparative example 3 provides an air annealing method for a Fe(Se,Te) superconducting thin film, comprising the following steps:

[0111] (1) Open the injection valve, place the Fe(Se,Te) film into the annealing chamber, and close the valve;

[0112] (2) Turn on the heating system, set it to heat from room temperature 25°C to 125°C in 40 minutes, and then keep it warm for 2 hours;

[0113] (4) Turn off the heating system and cool naturally to room temperature of 25°C;

[0114] (5) Take out the annealed Fe(Se,Te) film.

[0115] like Fig.10 As shown, the c-axis lattice constant after annealing is reduced to The crystallinity is improved. Fig.11 As shown, T c onset Rising to 18.54K, ΔT c Increased to 3.95K, by Fig.12 As shown, 4.2K self-field J c Reduced to 6.69MA / cm 2 , J under 2.58T magnetic field c Decrease by 0.

[0116] Comparative Example 4:

[0117] The lattice constant of the original unannealed film used in this comparative example is The rest are the same as in Example 1

[0118] like Fig.13 As shown, the c-axis lattice constant after annealing is reduced to The crystallinity is improved. Fig.11 As shown, T c onset From 16.79K to 9.35K, ΔT c Increased from 1.94K to 2.65K.

[0119] The present invention performs post-annealing treatment on the Fe(Se,Te) film in oxygen. The different oxygen flow rates in Examples 1-3 and the different annealing times in Examples 4-5 make the T of the Fe(Se,Te) superconducting film c and J c There are different degrees of improvement. After annealing in an oxygen flow rate of 210 SCCM at 4.2K, the J c Increased to 19.60MA / cm 2 , J under 9T magnetic field c Increased to 4.27MA / cm 2 From Comparative Example 1, it is known that a slightly lower annealing temperature can only increase T c , unable to improve J c From Comparative Example 2, we know that a slightly higher annealing temperature may significantly reduce the superconducting properties of the film. From Comparative Example 3, we know that after annealing in air, cThe decrease may be due to moisture destroying superconductivity. Comparative Example 4 shows that the superconducting performance of the film with a smaller c-axis lattice constant decreases after annealing. Therefore, for the Fe(Se,Te) film with a relatively large c-axis lattice constant, after annealing in an oxygen atmosphere at about 100°C, T c and J c All have increased.

[0120] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for oxygen annealing of a Fe(Se,Te) superconducting thin film, characterized in that: The steps include: (1) Place the Fe(Se,Te) film in an annealing chamber and evacuate the chamber; (2) continuously introducing a specific flow rate of oxygen into the annealing chamber; (3) heating to a specific annealing temperature and maintaining the temperature for a specific annealing time; (4) Cool naturally to room temperature; thus, the annealed Fe(Se,Te) film is obtained.

2. The oxygen annealing method of a Fe(Se,Te) superconducting thin film according to claim 1, characterized in that: The Fe(Se,Te) film described in step (1) is epitaxially grown on Hastelloy C276 coated with a CeO2 buffer layer using pulsed laser deposition (PLD).

3. The oxygen annealing method of a Fe(Se,Te) superconducting thin film according to claim 1, characterized in that: Step (1) evacuates the pressure to below 1 Pa, and during the subsequent annealing process, the vacuum pump is always kept open to allow oxygen to flow.

4. The oxygen annealing method of a Fe(Se,Te) superconducting thin film according to claim 1, characterized in that: In step (2), the oxygen flow rate is 28 SCCM to 561 SCCM.

5. The oxygen annealing method of a Fe(Se,Te) superconducting thin film according to claim 4, characterized in that: In step (2), the oxygen flow rate is 28 SCCM, 210 SCCM, and 561 SCCM.

6. The oxygen annealing method of a Fe(Se,Te) superconducting thin film according to claim 1, characterized in that: In step (3), the annealing temperature is 100° C. and the annealing time is 30 min to 4 h.

7. The oxygen annealing method of a Fe(Se,Te) superconducting thin film according to claim 6, characterized in that: The annealing time is 30min, 2h, and 4h.

8. The oxygen annealing method of a Fe(Se,Te) superconducting thin film according to claim 1, characterized in that: The heating rate in step (3) is 2-3°C / min.

9. The oxygen annealing method of a Fe(Se,Te) superconducting thin film according to claim 8, characterized in that: The heating rate in step (3) is 2.5°C / min.

10. The oxygen annealing method of a Fe(Se,Te) superconducting thin film according to claim 1, characterized in that: The thickness of the Fe(Se,Te) film in step (1) is 100-200nm, and the c-axis lattice constant is greater than

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