Method for reducing warping voltage of YBCO (Yttrium Barium Copper Oxide) nanowire
By using focused ion beams to locally and periodically irradiate YBCO nanowires with helium ion beams, the distribution of vortex pinning points was controlled, thus solving the problem of warping voltage in YBCO nanowires and improving the stability of superconducting performance and detection performance.
Patent Information
- Application Number
- CN202511757827.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-27
- Publication Date
- 2026-02-27
AI Technical Summary
Existing technologies struggle to effectively reduce the warping voltage of YBCO nanowires without compromising their superconducting properties, thus affecting their photodetection sensitivity and signal-to-noise ratio.
Focused ion beams were used to locally and periodically irradiate the YBCO nanowires with helium ions to control the distribution of vortex pinning points. Uniform pinning centers were introduced into the YBCO nanowires to restrict vortex motion.
This effectively reduced the warping voltage of YBCO nanowires while maintaining their superconducting properties, thus improving the signal-to-noise ratio and sensitivity of the detection signal.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of single photon detection, and particularly relates to a method for reducing the warping voltage of YBCO nanowires. BACKGROUND
[0002] Since the superconducting nanowire single photon detector (SNSPD) was first confirmed in 2001, it has become a key technology in the fields of quantum communication, quantum key distribution, satellite laser ranging, remote sensing and other frontier scientific fields due to its high system detection efficiency, low dark count rate, low timing jitter and wide detection spectrum. However, the SNSPD prepared by using low-temperature superconducting materials such as niobium nitride (NbN) and tungsten silicide (WSi) needs to be operated in an extremely low temperature environment (< 3 K), which limits the further effective application range of the SNSPD. Therefore, how to effectively improve the working temperature of the SNSPD is one of the important research directions. As a high-temperature superconducting material, yttrium barium copper oxide (YBCO) not only has a high critical transition temperature, but also can effectively improve the working temperature of the SNSPD. In addition, the advantages of large-area growth and short electrical-phonon relaxation time of YBCO can effectively expand the application range of the SNSPD.
[0003] At present, one method for realizing the SNSPD based on the YBCO material is to process an ultra-narrow YBCO nanowire with a hysteresis IV phenomenon by using an ultra-thin YBCO film (< 10 nm). The hysteresis IV phenomenon refers to that when the applied current exceeds the critical current Ic, the voltage will jump from zero to a certain value, indicating that the nanowire changes from a superconducting state to a normal state. Only when the applied current is less than the hysteresis current Ir, the voltage will return to zero, indicating that the nanowire changes from the normal state to the superconducting state, and the value of Ir is smaller than that of Ic. Ideally, the voltage of the nanowire is zero before the jump occurs. However, due to the reduction of the thickness of the YBCO film, the vortex motion in the processed nanowire will be more intense, resulting in the existence of a warping voltage before the jump occurs (Dobrovolskiy, O. V, et al. "Ultra-fast vortex motion in a direct-write Nb-Csuperconductor." Nature communications 11.1 (2020): 3291.). The existence of the warping voltage will produce a certain thermal effect on the nanowire, which will not only affect the light detection sensitivity of the YBCO nanowire, but also affect the signal-to-noise ratio of the detection signal.
[0004] The current method for reducing the lift-off voltage of the nanowire is to bind the movement of the vortex by introducing additional pinning centers in the nanowire. The common method for introducing additional pinning centers is ion implantation. Ion implantation is to place the nanowire sample in the ion implantation machine device, and to irradiate the whole nanowire device, so as to introduce additional pinning centers in the sample by ion bombardment. Due to the small ion radius and large ion implantation density, the effect on the superconducting nanowire is the overall optimization of the critical current Ic, but it is difficult to control the strength and uniformity of the vortex pinning point, and thus the lift-off voltage cannot be controlled.
[0005] Therefore, how to stably and effectively reduce the lift-off voltage of the ultra-thin YBCO nanowire while ensuring that the superconducting performance is almost unchanged is a problem to be solved at present. SUMMARY
[0006] In view of the problems in the background art, the purpose of the present application is to provide a method for reducing the lift-off voltage of YBCO nanowire by ion irradiation. The method uses focused ion beam (FIB) to perform local periodic irradiation of helium (He) ion beam, improves the uniformity of vortex pinning point distribution, and thus realizes the control of the lift-off voltage. At the same time, the superconducting performance of the ultra-thin YBCO nanowire is not damaged.
[0007] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:
[0008] A method for reducing the lift-off voltage of YBCO nanowire by ion irradiation, comprising the following steps:
[0009] Step 1. Preparing a YBCO thin film with a thickness not greater than 10 nm on the surface of a substrate;
[0010] Step 2. Preparing an amorphous YBCO protective layer on the surface of the YBCO thin film, which can effectively prevent the degradation of YBCO due to contact with the atmosphere during processing;
[0011] Step 3. Preparing a metal electrode on the ultra-thin YBCO thin film by means of stainless steel mask and evaporation;
[0012] Step 4. Preparing an actual processing area on the amorphous YBCO protective layer by means of photolithography and inductively coupled reactive ion etching (ICP-RIE);
[0013] Step 5. Preparing an ultra-thin YBCO nanowire in the processing area of step 4 by means of electron beam lithography (EBL) and ICP-RIE, and then removing the surface electron beam resist;
[0014] Step 6. Placing the ultra-thin YBCO nanowire obtained in step 5 in a focused ion beam irradiation device, and performing helium (He) ion implantation on the nanowire, and the implantation points are arranged in a periodic array.
[0015] Further, in step 1, the substrate includes but is not limited to magnesium oxide, lanthanum aluminate or strontium titanate substrate.
[0016] Further, in step 1, the thickness of the YBCO film ranges from 3-10 nm.
[0017] Further, in step 2, the thickness of the amorphous YBCO protective layer is not less than 8 nm, and the growth method is room temperature direct current magnetron sputtering.
[0018] Further, in step 3, the vacuum degree of the electron beam evaporation system cavity is not higher than 5x10 -4 Pa, and the electrode growth rate is 0.1-0.5 Å / s.
[0019] Further, in steps 4 and 5, the etching gas is a mixture of argon and chlorine gas, and the volume ratio of the two is Ar:Cl2=9:1, and the etching parameters are: ICP power is 800-1200 W, RF power is 80-120 W, and etching gas pressure is 1 mTorr.
[0020] Further, in step 6, the parameters of the focused ion beam process are: the dose range is 10 12 -10 16 ion / cm 2 , the residence time is 0.1-10 μs, the beam size is 1-10 pA, the ion acceleration voltage is 10-30 kV, and the spacing between adjacent injection points is 30-500 nm.
[0021] The mechanism of the present application is: under a fixed current bias, weak vortex pinning points are easy to lose superconductivity and produce local voltage, strong vortex pinning points still have superconductivity, and the uneven distribution of strong and weak vortex pinning points causes the lifting voltage in the IV characteristic curve. The present application uses He ion beam to perform periodic irradiation, and the low-energy He ion performs local periodic bombardment on the YBCO nanowire. This bombardment will produce new pinning centers uniformly distributed inside the YBCO nanowire, and the energy of the vortex pinning points introduced by the bombardment is uniform. Therefore, the present application adjusts the distribution of the pinning point position and the uniformity of the energy to realize the regulation of the lifting voltage.
[0022] In summary, due to the adoption of the above technical solutions, the present application has the following advantages:
[0023] The application utilizes the focused He ion beam irradiation technology to introduce additional pinning centers in the ultrathin YBCO nanowire, limit the movement of the vortex in the nanowire, and effectively reduce the kick voltage before the voltage jump of the YBCO nanowire; meanwhile, the ion radius of He is small, the diffusion range in the ultrathin YBCO nanowire is smaller, and the influence of ion diffusion on the superconducting performance of the ultrathin YBCO nanowire can be effectively reduced. BRIEF DESCRIPTION OF DRAWINGS
[0024] Figure 1 The RT characteristic diagram of the YBCO nanowire with different irradiation doses in the embodiment 1 of the application.
[0025] Figure 2 The IV characteristic comparison diagram of the nanowire before and after irradiation in the embodiment 2 of the application with the irradiation dose of 10 14 ion / cm 2 .
[0026] Figure 3 The IV characteristic comparison diagram of the nanowire before and after irradiation in the embodiment 2 of the application with the irradiation dose of 10 15 ion / cm 2 .
[0027] Figure 4 The IV characteristic comparison diagram of the nanowire before and after irradiation in the embodiment 2 of the application with the irradiation dose of 10 16 ion / cm 2 .
[0028] Figure 5 The RT characteristic diagram of the YBCO nanowire after irradiation in the embodiment 3 of the application with different line widths.
[0029] Figure 6 The IV characteristic comparison diagram of the YBCO nanowire before and after irradiation in the embodiment 3 of the application with the line width of 800 nm.
[0030] Figure 7 The IV characteristic comparison diagram of the YBCO nanowire before and after irradiation in the embodiment 3 of the application with the line width of 600 nm.
[0031] Figure 8 The IV characteristic comparison diagram of the nanowire before and after irradiation in the comparative example 2 of the application with the irradiation dose of 10 11 ion / cm 2 . DETAILED DESCRIPTION
[0032] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below by combining with the embodiments and drawings.
[0033] Embodiment 1
[0034] A method for reducing the warping voltage of YBCO nanowires, comprising the following steps:
[0035] Step 1: clean the strontium titanate substrate with a thickness of 500 μm with acetone, ethanol and deionized water, and then dry it with a nitrogen gun to remove the water vapor on the surface of the substrate;
[0036] Step 2: grow a 10 nm thick YBCO film on the surface of the strontium titanate substrate cleaned in step 1 by using a direct current magnetron sputtering method, the inside of the cavity is O2:Ar = 1:3 mixed gas, the gas pressure is 30 Pa, the sputtering power is 125 W, the cavity temperature is 802 ℃, and the film growth rate is calibrated to 0.33 nm / min, after 30 min of deposition, a 10 nm ultra-thin YBCO film is obtained; after the film growth is completed, the cavity temperature is reduced to room temperature, and a 10 nm thick amorphous YBCO protective layer is grown on the YBCO film under the same gas conditions and sputtering power while keeping the cavity temperature basically unchanged;
[0037] Step 3: clean the surface residual particles of the sample obtained in step 2 in isopropanol, and then dry it with a nitrogen gun to remove the residual isopropanol on the surface of the sample; then spin-coat ZEP520A electron beam resist on the surface of the sample with a thickness of 100 nm, and then heat it on a baking table at 180 ℃ for 3 min;
[0038] Step 4: pattern the resist: design a single-line structure for the nanowire structure with a line width of 1 μm, and import the design into the EBL system to start patterning the electron beam resist at an exposure voltage of 20 kV;
[0039] Step 5: after the electron beam exposure is completed, develop the resist with ZED-N50 developer at room temperature for 3 min, continuously shake the sample during the development process to ensure that the ZEP520A is completely developed, then immerse the sample in isopropanol for 15 s, and finally rinse the surface of the sample with deionized water for 15 s, then dry it with a nitrogen gun to remove the residual chemical reagents on the sample;
[0040] Step 6: transfer the micro-nano structure on the electron beam resist to the YBCO film by ICP-RIE technology with Ar:Cl2 = 9:1 as the etching gas, wherein the ICP power is 1000 W and the RF power is 100 W; during the etching process, the tray temperature needs to be maintained at -20 ℃ by cooling liquid; after the etching is completed, the sample is taken out, and at this time, a high-precision nanowire structure can be obtained on the ultra-thin YBCO film;
[0041] Step 7: The nanowire sample is placed in the ultraviolet light irradiation system for irradiation for 5 min, and finally the sample surface is soaked in acetone to remove the residual electron beam lithography reagent, and finally a high-precision ultrathin YBCO nanowire structure is obtained;
[0042] Step 8: The nanowire sample is placed in the irradiation system, and the sample is irradiated by an ion beam, wherein the type of ion beam used is He ion beam, the irradiation dose is 10 14 ion / cm 2 , the residence time is 0.1 μs, the beam current is 1 pA, the ion acceleration voltage is 30 Kev, the spacing between adjacent injection points is 30 nm, and the YBCO nanowire with low voltage kick is obtained after irradiation.
[0043] The RT characteristic diagram of the YBCO nanowire prepared in this embodiment under different irradiation doses is shown in Figure 1 As the irradiation dose increases, the defects in the YBCO nanowire also increase, and the T c0 also decreases, but the T c0 of the nanowire under the three doses is above 60 K, indicating that the three nanowires have excellent superconducting performance after irradiation.
[0044] Example 2
[0045] The YBCO nanowire is prepared according to Example 1 and irradiated, only the irradiation dose in step 8 is changed to 10 15 ion / cm 2 and 10 16 ion / cm 2 , and the remaining steps remain unchanged.
[0046] Figure 2 、 Figure 3 and Figure 4 are the IV characteristic changes of the sample before and after irradiation under different irradiation doses. It can be seen that the sample before irradiation has a significant voltage value at low bias current, and after irradiation, the introduction of additional pinning centers limits the movement of magnetic vortexes, so the overall sample has no significant voltage value before voltage jump, and only when the bias current exceeds the I c of the sample, there is a significant voltage value. It shows that the present scheme can realize the regulation of the kick voltage.
[0047] Example 3
[0048] The YBCO nanowire is prepared according to Example 1 and irradiated, only the nanowire width in step 4 is changed to 600 nm and 800 nm, and the remaining steps remain unchanged.
[0049] Figure 5The RT characteristics of the irradiated samples of different line widths show that the samples of different line widths still have high T c0 after irradiation, indicating that the local ion irradiation of the application does not significantly affect the superconducting performance of the YBCO nanowires. Figure 6 and Figure 7 The IV characteristics of the samples before and after irradiation at 800 nm and 600 nm, respectively, show that the onset voltage of the nanowires of different line widths after irradiation is significantly lower than that before irradiation.
[0050] Example 4
[0051] The YBCO nanowires were prepared according to Example 1 and irradiated, and only the spacing between adjacent injection points in step 8 was adjusted to 500 nm, and the other steps remained unchanged.
[0052] Comparative Example 1
[0053] The YBCO nanowires were prepared according to Example 1, and only step 8 was not performed, and the other steps remained unchanged.
[0054] The IV characteristics of the unirradiated device did not change significantly regardless of how long the sample was placed.
[0055] Comparative Example 2
[0056] The YBCO nanowires were prepared according to Example 1, and only the irradiation dose in step 8 was changed to 10 11 ion / cm 2 , and the other steps remained unchanged.
[0057] The IV characteristics of the nanowires before and after irradiation in Comparative Example 2 are shown in Figure 8 The figure shows that the onset voltage of the nanowires before and after irradiation at low dose does not change significantly, proving that the number of pinning centers generated in the YBCO nanowires by low-dose ion irradiation is not enough to effectively limit the movement of vortices, so the value of the onset voltage before and after irradiation is basically unchanged.
[0058] The above is only a specific embodiment of the application, and any feature disclosed in this specification can be replaced by other equivalent or similarly intended alternative features unless specifically stated; all features disclosed, or steps in all methods or processes, except mutually exclusive features and / or steps, can be combined in any way.
Claims
1. A method of ion irradiation to reduce the critical voltage of YBCO nanowires, characterized in that, Includes the following steps: Step 1. Prepare a YBCO thin film with a thickness of no more than 10 nm on the substrate surface; Step 2. Prepare an amorphous YBCO protective layer on the surface of the YBCO thin film; Step 3. Prepare metal electrodes on ultrathin YBCO films using vapor deposition; Step 4. The actual processing area is prepared on the surface of the amorphous YBCO protective layer by photolithography and inductively coupled reactive ion etching; Step 5. In the processing area of step 4, ultrathin YBCO nanowires are prepared by electron beam lithography and inductively coupled reactive ion etching, and then the photoresist is removed; Step 6. Place the ultrathin YBCO nanowires obtained in Step 5 in a focused ion beam irradiation device to implant helium ions into the nanowires, with the implantation points arranged in a periodic array.
2. The method for reducing the warping voltage of YBCO nanowires by ion irradiation as described in claim 1, characterized in that, In step 1, the substrate includes, but is not limited to, magnesium oxide, lanthanum aluminate, or strontium titanate substrates.
3. The method for reducing the warping voltage of YBCO nanowires by ion irradiation as described in claim 1, characterized in that, In step 1, the thickness of the YBCO film ranges from 3 to 10 nm.
4. The method for reducing the warping voltage of YBCO nanowires by ion irradiation as described in claim 1, characterized in that, In step 2, the thickness of the amorphous YBCO protective layer is not less than 8 nm, and the growth method is room temperature DC magnetron sputtering.
5. The method for reducing the warping voltage of YBCO nanowires by ion irradiation as described in claim 1, characterized in that, In step 3, the vacuum degree of the electron beam evaporation system cavity is not higher than 5x10 -4 Pa, and the electrode growth rate is 0.1-0.5 A / s.
6. The method for reducing the warping voltage of YBCO nanowires by ion irradiation as described in claim 1, characterized in that, In steps 4 and 5, the etching gas is a mixture of argon and chlorine, with a volume ratio of Ar:Cl2 = 9:
1. The etching parameters are: ICP power of 800-1200 W, RF power of 80-120 W, and etching pressure of 1 mTorr.
7. The method for reducing the warping voltage of YBCO nanowires by ion irradiation as described in claim 1, characterized in that, In step 6, the parameters of the focused ion beam process are: a dose range of 10 12 -10 16 ion / cm 2 , a residence time of 0.1-10 μs, a beam current of 1-10 pA, an ion acceleration voltage of 10-30 kV, and a spacing between adjacent implantation points of 30-500 nm.