Large-size growth method of V3O5 crystal with memristor function

Abstract

The invention discloses a large-size growth method of a V3O5 crystal with memristor functional characteristics. The chemical vapor transport method is combined with double-temperature-zone control, growth of the large-size V3O5 crystal is successfully achieved, the obtained V3O5 crystal is in a block shape, and the length size can reach 0.6 cm. The obtained crystal presents insulator-metal transformation under the driving voltage of 8 V, the current suddenly changes from 10 <-2 > mA to 102 mA magnitude, the conductivity change rate exceeds 104, and the crystal is suitable for manufacturing high-performance memristors.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of crystal growth, and relates to a growth method of V3O5 crystal, in particular to a large-size growth method of V3O5 crystal with a memory resistor function. BACKGROUND

[0002] Metal-insulator transition (MIT) is a reversible transition between metal and insulator states under external stimuli, which is accompanied by a large change in electrical conductivity, and thus has wide application prospects in energy storage, intelligent devices, neuromorphic computing and sensors. Vanadium oxide is a typical strongly correlated electron material, which has diverse metal-insulator transition temperatures, transition amplitudes and driving modes, and thus has been an important system for MIT material research for a long time.

[0003] Vanadium oxide has a complex homogenous polymorphic structure system, including Magnéli phases with a chemical formula of V n O 2n-1 (n=3, 4, …, 9), and the phase transition temperatures and electrical properties of different crystal phases differ significantly. However, due to the limitations of crystal growth methods, raw material properties and phase stability, the vanadium oxide single crystals obtained at present have great differences in size, purity and defect density.

[0004] Among the many vanadium oxide crystal phases, the conductivity change rate of V3O5 is higher than that of VO2, and V3O5 also has the advantages of small phase transition internal stress (about 0.21%), and can be driven by electric field, optical field, magnetic field and other physical fields at room temperature, which helps to reduce energy consumption and improve cycle life. In addition, V3O5 is rich in reserves, low in cost and high in energy density, and has important competitiveness in the fields of energy storage and devices.

[0005] However, the existing technology can only obtain small-size V3O5, and the crystal quality is not high, which is difficult to meet the performance requirements of the memory resistor device in the high-density neuromorphic computing chip. Therefore, how to obtain large-size and high-quality V3O5 single crystal has become a technical problem to be solved in the field. SUMMARY

[0006] In order to improve the above technical problems, the present application provides a large-size V3O5 crystal, which has a memory resistor function and is prepared by optimizing the growth conditions through chemical vapor transport method.

[0007] The present application provides a large-size V3O5 crystal, and the length of the V3O5 crystal is millimeter level, for example, greater than 3 mm, for example, not less than 4 mm, 5 mm or 6 mm.

[0008] According to an embodiment of the present invention, the V3O5 crystal undergoes a significant insulator-metal transition at a relatively small driving voltage (5~10V, for example 8V), with its current decreasing from 10V to 10V. -2 A sudden jump from the mA level to 10 2 The order of mA, with a rate of change exceeding 10 4 It exhibits a large rate of change in conductivity.

[0009] According to an embodiment of the present invention, the V3O5 crystal can grow to a length of 0.6 cm.

[0010] According to an embodiment of the present invention, the natural growth surfaces of the V3O5 crystal are (110) and (001) surfaces.

[0011] According to an embodiment of the present invention, the (110) facet of the V3O5 crystal has substantially the following characteristics: Figure 2 The XRD pattern shown in (a) is shown in the image.

[0012] According to an embodiment of the present invention, the (001) plane of the V3O5 crystal has substantially the following characteristics: Figure 2 The XRD pattern shown in (b) is shown in the image.

[0013] According to an embodiment of the present invention, the V3O5 crystal has substantially the following characteristics: Figure 3 The temperature-dependent X-ray diffraction angle and intensity distribution are shown in (a).

[0014] According to an embodiment of the present invention, the V3O5 crystal belongs to the monoclinic crystal system, space group [space group missing]. P2 / c .

[0015] According to an embodiment of the present invention, the V3O5 crystal is a single crystal.

[0016] According to an embodiment of the present invention, the V3O5 crystal undergoes a metal-insulator phase transition (MIT) at 400~450K (e.g., 420K).

[0017] This invention also provides a method for preparing V3O5 crystals, the method comprising the following steps: Vanadium powder and vanadium pentoxide are mixed and sintered to obtain vanadium pentoxide powder. The vanadium pentoxide powder is then mixed with tellurium tetrachloride, ground, packaged, and placed in a dual-temperature zone tube furnace. After heating, holding, and cooling, the V3O5 crystals are obtained.

[0018] According to an embodiment of the present invention, the sintering reaction is carried out in a muffle furnace.

[0019] According to an embodiment of the present invention, the sintering reaction comprises two stages: The sintering temperature of the first stage is 600-700℃, for example 600℃, 650℃; the sintering time is 15-35h, for example 20h, 24h, 30h; The sintering temperature of the second stage is 900-1050℃, for example 900℃, 950℃, 1000℃; the sintering time is 80-120h, for example 90h, 100h, 110h.

[0020] According to an embodiment of the present application, the molar ratio of the vanadium powder and the di vanadium pentoxide is 1:(0.9-1.1), preferably 1:1.

[0021] According to an embodiment of the present application, the tellurium tetrachloride is used as a transport agent. Preferably, the mass ratio of the V3O5 powder and the tellurium tetrachloride is 10:(1-1.2), for example 10:1, 10:1.2.

[0022] According to an embodiment of the present application, the mixture of the vanadium trioxide powder and the tellurium tetrachloride is packaged in a quartz tube, and the pressure inside the tube is kept less than 10 -2 Pa.

[0023] According to an embodiment of the present application, the volume concentration of the tellurium tetrachloride is 50-80mg / mL, based on the volume of the quartz tube; for example 60-70mg / mL.

[0024] According to an embodiment of the present application, the temperature reached by the heating requires that the temperature difference between the raw material end (i.e. the high temperature end) and the growth end (i.e. the low temperature end) of the double-temperature zone tube furnace is 200℃.

[0025] According to an embodiment of the present application, the temperature of the raw material end of the double-temperature zone tube furnace is 1000-1100℃, and the temperature of the growth end is 800-900℃; the raw material end can be for example 1000℃, 1100℃, and the growth end can be for example 800℃, 900℃.

[0026] According to an embodiment of the present application, the holding time is not less than 120h, for example not less than 144h, and is exemplarily 168h.

[0027] According to an embodiment of the present application, the cooling is natural cooling to room temperature.

[0028] According to an embodiment of the present application, the preparation method comprises the following steps: (S1) placing vanadium powder and di vanadium pentoxide powder in a first quartz tube; (S2) placing the first quartz tube of step (S1) in a muffle furnace, and after the sintering reaction, cooling to obtain V3O5 powder; Preferably, the sintering reaction comprises two stages: The sintering temperature of the first stage is 550-650℃, and the sintering time is 20-30h; The sintering temperature of the second stage is 900-1000℃, and the sintering time is 90-110h; (S3) mixing and grinding the V3O5 powder and tellurium tetrachloride, and placing the obtained mixture in a second quartz tube, keeping the pressure in the tube less than 10 -2 Pa; (S4) placing the second quartz tube in step (S3) in a double-temperature-zone tube furnace, and growing, keeping warm and cooling to prepare the V3O5 crystal; The temperature difference between the raw material end (i.e. high-temperature end) and the growth end (i.e. low-temperature end) of the double-temperature-zone tube furnace is 200℃, and the temperature of the raw material end is 1000-1100℃; The mass ratio of the V3O5 powder and tellurium tetrachloride is 10:(1-1.2), or the volume concentration of the tellurium tetrachloride is 50-80mg / mL, based on the volume of the second quartz tube; The keeping-warm growing time is not less than 120h.

[0029] According to the embodiments of the present application, in steps (S1) and (S3), the first and second quartz tubes are washed with organic solvent and deionized water, and dried in an oven to remove the water in the quartz tubes.

[0030] According to the embodiments of the present application, in step (S1), the organic solvent is anhydrous ethanol. The content of the organic solvent is not particularly limited, as long as it can clean the quartz tube.

[0031] According to the embodiments of the present application, the first quartz tube is 24 cm long, necked at 12 cm, 30 mm in diameter, 2mm in wall thickness, and round bottomed.

[0032] According to the embodiments of the present application, the first quartz tube is 20 cm long, necked at 10 cm, 20 mm in diameter, 2mm in wall thickness, and round bottomed.

[0033] According to the embodiments of the present application, the V3O5 powder and tellurium tetrachloride can be mixed uniformly in a mortar.

[0034] According to the exemplary embodiments of the present application, the preparation method of the V3O5 crystal specifically comprises the following steps: 1) washing the first and second quartz tubes with deionized water and organic solvent (e.g. ethanol) in sequence, and drying the water in the two quartz tubes in an oven; 2) Preparation of growth raw materials: Weigh vanadium (V, 2.547 g) and vanadium pentoxide powder (V2O5, 9.094 g), mix them evenly by grinding in a mortar and pestle, and put them into the first quartz tube prepared in step 1); place the first quartz tube in a muffle furnace, sinter at 600℃ for 24 h, and then sinter at 950℃ for 100 h, and cool down to obtain V3O5 powder; 3) The V3O5 powder and 1400 mg TeCl4 were placed in an agate mortar and ground together for 3 minutes. The resulting mixture was then sealed into a second quartz tube, maintaining an internal pressure of less than 10 ppm. -2 Pa; 4) The encapsulated second quartz tube is placed in a dual-temperature zone tube furnace with a raw material end temperature of 1100℃ and a growth end temperature of 900℃. After a 7-day growth cycle, the V3O5 crystal is obtained after natural cooling.

[0035] According to an embodiment of the present invention, the V3O5 crystal has the limitations shown above.

[0036] The present invention also provides the application of the above-mentioned V3O5 crystal in the preparation of electronic devices; for example, the electronic device is a computing chip, preferably a memristor.

[0037] The present invention also provides an electronic device (e.g., a computing chip, preferably a memristor) containing or prepared from the above-mentioned V3O5 crystal. Beneficial effects

[0038] (1) The present invention adopts chemical vapor transport method combined with dual temperature zone and transport agent dosage control, and successfully realizes the growth of large-size, highly uniform, regular and structurally complete V3O5 crystals. Compared with traditional methods, the crystal size can reach 0.6cm, which significantly improves the crystal scale, structural regularity and integrity.

[0039] (2) The present invention optimizes the oxygen-free environment and temperature gradient (200℃), effectively reducing dislocation density and impurity phase generation, and ensuring the high purity and structural integrity of the single crystal.

[0040] (3) In this invention, under an 8 V driving voltage, the V3O5 crystal exhibits a high 10 4 The conductivity change rate is superior to that of small-sized crystals in existing technologies, providing a better material platform for memristor applications in high-density neuromorphic computing chips.

[0041] (4) The growth process of the present invention overcomes the difficulty of large-size growth caused by the volatility of vanadium in the prior art.

[0042] (5) The V3O5 crystal material prepared by the present invention can be used in electronic device applications and provides raw materials for the application of memristors.

[0043] (6) The transport agent method used in this invention has the advantages of low cost and easy operation. Attached Figure Description

[0044] Figure 1 This is a photograph of V3O5 crystals grown by chemical vapor transport (scale bar: 5 mm).

[0045] Figure 2 (a) XRD pattern of the (110) plane of naturally grown V3O5 crystal; (b) XRD pattern of the (001) plane.

[0046] Figure 3 (a) Temperature-dependent X-ray diffraction angle and intensity distribution; (b)~(d) are enlarged views of the (200) plane, (002) plane and (020) plane respectively.

[0047] Figure 4 The current-voltage curve of V3O5 crystal is shown.

[0048] Figure 5 The X-ray diffraction angle distribution of V3O5 crystals was measured after grinding into powder.

[0049] Figure 6 Photographs of V3O5 crystals obtained under the conditions of Comparative Example 1 (scale bar is 5 mm).

[0050] Figure 7 Photographs of V3O5 crystals obtained under the conditions of Comparative Example 2 (scale bar is 5 mm). Detailed Implementation

[0051] The V3O5 provided by this invention is a monoclinic crystal system (space group 1). P2 / c Vanadium oxide materials undergo a metal-insulator phase transition (MIT) at approximately 420 K, with a conductivity change rate reaching 10⁻⁶. 4 ~10 5 The magnitude is higher than 10 of VO2. 3 The phase transition is on the order of magnitude of a magnetic field. This phase transition process is accompanied by a significant jump in electrical conductivity and exhibits relatively low internal phase transition stress (approximately 0.21%), allowing the crystal to maintain structural stability during the transition. Furthermore, V3O5 can be driven by multiple physical fields, including electric, optical, and magnetic fields, at room temperature, enabling low-energy-consumption phase transition control. This offers significant advantages in energy storage, smart devices, and neuromorphic computing. As a mixed-valence vanadium oxide, the phase transition mechanism of V3O5 originates from strongly correlated electron effects and lattice-charge-spin coupling. Specifically, near the phase transition temperature, the electronic correlation between vanadium ions leads to the transition from the insulating Mott state to the metallic state.

[0052] The above characteristics demonstrate that fabricating large-size V3O5 single crystals is both theoretically feasible and practically significant for improving device performance. Firstly, large-size single crystals exhibit a higher on / off ratio and lower dislocation density compared to small-size crystals, which can significantly reduce energy loss and improve cycle life in memristors. Experimental verification shows that at an 8 V drive voltage, the crystal current increases from 10... -2 mA mutation to 10 2 mA, rate of change of conductivity exceeding 10 4 It is far superior to existing small-sized samples of 0-3 mm.

[0053] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0054] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0055] High-purity V powder and V2O5 powder were used as raw materials in the experiment, and the transport agent TeCl4 was also a high-purity reagent. The quartz tube for growing crystals was made of high-purity quartz material.

[0056] First quartz tube: 24 cm long, necked at 12 cm, 30 mm in diameter, 2 mm in wall thickness, round bottom; Second quartz tube: 20 cm long, necked at 10 cm, 20 mm in diameter, 2 mm in wall thickness, round bottom.

[0057] X-ray diffraction test: Bruker D8 Advanced; Variable-temperature X-ray diffraction test: Bruker D8 Advanced; Current-voltage curve test: Keithley 2460 source meter. Example 1

[0058] The first and second quartz tubes were cleaned with deionized water and anhydrous ethanol, and then dried in an oven. 2.547 g of V powder and 9.094 g of V₂O₅ powder were weighed, ground and mixed evenly in a mortar, and then placed into a pre-prepared first quartz tube. The first quartz tube was then placed in a muffle furnace and sintered at 600℃ for 24 h, followed by sintering at 950℃ for 100 h. After cooling, V₃O₅ powder was obtained. The V₃O₅ powder was then removed, and at a mass ratio of V₃O₅ powder to TeCl₄ of 10:1.2, it was ground and mixed with 1400 mg of TeCl₄ in an agate mortar for 3 minutes. The mixed powder was then placed into a pre-treated second quartz tube, maintaining an internal pressure of less than 10 kJ / kg. -2 A sealed second quartz tube was placed horizontally in a dual-temperature zone tube furnace. The temperature was set at 1100℃ for the raw material end (high-temperature zone) and 900℃ for the growth end (low-temperature zone), maintaining a temperature gradient of 200℃. The volume concentration of TeCl4 in the second quartz tube was approximately 70 mg / mL. After a 7-day growth cycle, natural cooling yielded large-sized V3O5 crystals. The V3O5 crystals were separated from the transport agent to determine their structural composition, allowing for testing of the insulator-metal transition effect.

[0059] Figure 1 The image shows a photograph of the V3O5 crystals obtained in Example 1. The black areas with a metallic luster are crystal samples with a growth length of 0.6 cm. The crystals are columnar with a uniform and regular structure.

[0060] like Figure 2 As shown in (a), X-ray diffraction (XRD) analysis showed that the crystal prepared above was a monoclinic phase, and the diffraction peaks corresponded one-to-one with the standard cards; and its exposed natural growth surface was (110).

[0061] like Figure 2 As shown in (b), X-ray diffraction (XRD) analysis showed that the crystal prepared above was a monoclinic phase, and the diffraction peaks corresponded one-to-one with the standard cards; and its exposed natural growth surface was (001).

[0062] As shown in Figure 3, the variable-temperature X-ray diffraction (XRD) data indicates that the prepared polycrystalline powder is a single-phase V3O5 without other impurities. It undergoes a first-order structural phase transition (i.e., the transition from the insulating Mott state to the metallic state) near 420 K, with a lattice constant change of less than 0.3%, exhibiting small lattice distortion.

[0063] like Figure 4 As shown, the current-voltage curve data indicate that at a driving voltage of 8 V, the V3O5 crystal sample undergoes a significant insulator-metal transition, with the current increasing from 10 V. -2 The order of mA suddenly jumps to 10.2 mA level, conductivity change rate exceeding 10 4 It exhibits excellent electrical performance.

[0064] like Figure 5 As shown, the data is the X-ray diffraction angle distribution of the synthesized V3O5 crystal ground into powder, which is consistent with the V3O5 standard data card. There is no second phase, which indicates that the sample is a single crystal.

[0065] To demonstrate the necessity of the specific parameter range of this invention, the following comparative examples are provided. Comparative Example 1

[0066] The same raw materials, apparatus and process as in Example 1 of this invention are used, the only difference being that: the growth end temperature is set to 950 °C, the raw material end temperature is set to 1050 °C, and 931 mg of TeCl4 is used as the transport agent, that is, the mass ratio of V3O5 powder to TeCl4 is 10:0.8 (the volume concentration in the second quartz tube is about 46.6 mg / mL).

[0067] Result: Under these conditions, only the following can be obtained: Figure 6 The V3O5 crystal sample shown has a maximum size of less than 5 mm, and its shape is non-uniform and irregular, making it unsuitable for memristor fabrication. This result demonstrates that when the transport agent concentration is too low and the temperature difference is small, the crystal growth driving force is insufficient, making it difficult to achieve the growth of large-size crystals. Comparative Example 2

[0068] The same raw materials, apparatus and process as in Example 1 of this invention are used, the only difference being that: the growth end temperature is set to 950 °C, the raw material end temperature is set to 1050 °C, and 1630 mg of TeCl4 is used as the transport agent, that is, the mass ratio of V3O5 powder to TeCl4 is 10:1.4 (the volume concentration in the second quartz tube is about 81.5 mg / mL).

[0069] Result: Under these conditions, the following was observed at the growth end: Figure 7 The V3O5 crystal shown is less than 3 mm in size, and its shape is uneven and irregular, failing to meet the requirements for high-performance memristors. This result demonstrates that increasing the transporter concentration is also detrimental to the stable growth of large-sized crystals.

[0070] A comparison of Example 1 with Comparative Examples 1 and 2 shows that changing the amount of transport agent and the temperature in both temperature zones cannot achieve the controllable preparation of large-size V3O5 single crystals. This invention overcomes the shortcomings of existing technologies by synergistically optimizing the temperature gradient and transport agent concentration, successfully achieving the growth of large V3O5 single crystals.

[0071] The embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing V3O5 crystals, characterized in that, The preparation method includes the following steps: Vanadium powder and vanadium pentoxide are mixed and sintered to obtain vanadium pentoxide powder. The vanadium pentoxide powder is then mixed with tellurium tetrachloride, ground, packaged, and placed in a dual-temperature zone tube furnace. After heating, holding, and cooling, the V3O5 crystal is obtained. The length of the V3O5 crystal is greater than 3 mm, and preferably the V3O5 crystal is a single crystal.

2. The preparation method according to claim 1, characterized in that, The sintering reaction is carried out in a muffle furnace.

3. The preparation method according to claim 1, characterized in that, The sintering reaction includes two stages: The sintering temperature in the first stage is 600~700℃, and the sintering time is 15~35h; The sintering temperature for the second stage is 900~1050℃, and the sintering time is 80~120h.

4. The preparation method according to claim 1, characterized in that, The molar ratio of vanadium powder to vanadium pentoxide is 1:(0.9~1.1). And / or, the mass ratio of the V3O5 powder to tellurium tetrachloride is 10:(1~1.2).

5. The preparation method according to claim 1, characterized in that, A mixture of vanadium pentoxide powder and tellurium tetrachloride was encapsulated in a quartz tube, maintaining an internal pressure of less than 10. -2 Pa.

6. The preparation method according to claim 1, characterized in that, The required heating temperature is as follows: the temperature difference between the raw material end and the growth end of the dual-temperature zone tube furnace is 200℃. For example, the raw material end temperature of the dual-temperature zone tube furnace is 1000~1100℃, and the growth end temperature is 800~900℃. And / or, the heat preservation time is not less than 120 hours; And / or, the cooling is natural cooling to room temperature.

7. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (S1) Place vanadium powder and vanadium pentoxide powder in the first quartz tube; (S2) The first quartz tube from step (S1) is placed in a muffle furnace, sintered, and then cooled to obtain V3O5 powder. The sintering reaction includes two stages: The sintering temperature in the first stage is 550~650℃, and the sintering time is 20~30h; The sintering temperature for the second stage is 900~1000℃, and the sintering time is 90~110h; (S3) The V3O5 powder and tellurium tetrachloride are mixed and ground, and the resulting mixture is placed in a second quartz tube, maintaining the pressure inside the tube at less than 10. -2 Pa; (S4) The second quartz tube from step (S3) is placed in a dual-temperature zone tube furnace, and the V3O5 crystal is prepared by heating, heat preservation growth and cooling. The temperature difference between the raw material end and the growth end of the dual-temperature zone tube furnace is 200°C, and the temperature of the raw material end is 1000~1100°C. The heat preservation and growth time shall not be less than 120 hours; The mass ratio of V3O5 powder to tellurium tetrachloride is 10:(1~1.2).

8. The preparation method according to claim 7, characterized in that, In steps (S1) and (S3), the first and second quartz tubes are first washed with organic solvent and deionized water and then dried in an oven.

9. The application of the V3O5 crystal obtained by the preparation method according to any one of claims 1-8 in the preparation of electronic devices; Preferably, the electronic device is a computing chip, and more preferably a memristor.

10. An electronic device comprising V3O5 crystals obtained by the preparation method according to any one of claims 1-8; Preferably, the electronic device is a computing chip, and more preferably a memristor.

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