Surface-engineered two-dimensional titanium carbide memristor and preparation and application thereof

Abstract

The application belongs to the technical field of binary data storage, and particularly relates to a surface engineering modified two-dimensional titanium carbide memristor and a preparation and application thereof. The surface engineering modified two-dimensional titanium carbide memristor comprises a conductive substrate layer, a metal electrode layer and a functional film layer arranged between the conductive substrate layer and the metal electrode layer; the functional film layer comprises a modified two-dimensional titanium carbide layer and graphene oxide layers arranged on two sides of the modified two-dimensional titanium carbide layer, and the modified two-dimensional titanium carbide layer is a lapis lazuli blue modified two-dimensional titanium carbide layer. The application solves the problem of the two-dimensional titanium carbide metal conductivity through surface engineering modification, widens the application of the two-dimensional titanium carbide in the data storage field, and solves the problem of unstable performance of the single-layer structure two-dimensional titanium carbide memristor through the strategy of the laminated structure, and is expected to be applied in the storage field.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of binary data storage, and particularly relates to a surface engineering modified two-dimensional titanium carbide memristor and a preparation and application thereof. BACKGROUND

[0002] Traditional flash memory devices are difficult to meet the requirements of information storage technology in the future artificial intelligence era. Memristors have attracted great interest from academia and industry due to their simple structure, good scalability and potential for integration of storage and computing, and can meet the demand for ultra-high density information storage. A memristor is usually composed of a metal / insulator / metal (MIM) three-layer structure, which exhibits resistance switching behavior to realize data writing and storage. Due to its low operating voltage, fast switching speed, excellent durability and compatibility with traditional complementary metal-oxide-semiconductor (CMOS), the memristor is becoming the next generation of scalable non-volatile storage technology.

[0003] Two-dimensional nanomaterials have significant advantages over three-dimensional bulk materials due to their unique structure and photoelectric properties. Their planar structure endows them with excellent compatibility with traditional wafer semiconductor technology. In recent years, two-dimensional nanomaterials have made great progress in the field of nanoelectronic devices. Two-dimensional titanium carbide (MXenes) is a two-dimensional (2D) nanomaterial composed of transition metal carbides with multiple atomic layers. However, due to its metal-like conductivity, its development in the field of semiconductor electronic devices is limited. In recent years, different etching methods of MXene have resulted in different functional groups on the surface of MXene, which provides an opportunity for further modification of MXene nanosheets and makes it possible to apply MXene in the field of electronic memristors. In recent years, researchers have developed many inorganic-organic hybrid materials with controllable structure and morphology, which have been widely used in various fields. First, there are few reports on the surface engineering modification of MXene in non-volatile resistive random access memory (RRAM). In order to further expand the application of MXene in the field of information storage, new materials are needed to modify two-dimensional titanium carbide (Ti3C2T x -MXene) to change its band gap so that it can be applied in the field of electronics. Second, most two-dimensional memristors are widely considered to be ion migration type, which usually uses active metals (such as silver and copper) as electrodes, often leading to uncontrollable migration of metal ions and chaotic growth of metal conductive filaments, thereby reducing the stability of device performance and even causing degradation and failure of the device. The above problems pose great challenges to the realization of high-performance storage of two-dimensional memristors. Therefore, it is urgent to propose an effective strategy to prepare a two-dimensional memristor with stable bistable switching and controllable ion migration. SUMMARY

[0004] The present application aims to solve the above problems, and provides a preparation method of a surface-engineered two-dimensional titanium carbide memristor and an application thereof, so as to realize high-performance storage.

[0005] According to the technical scheme of the present application, the surface-engineered two-dimensional titanium carbide memristor comprises a conductive substrate layer, a metal electrode layer, and a functional film layer arranged between the conductive substrate layer and the metal electrode layer; the functional film layer comprises a modified two-dimensional titanium carbide layer and a graphene oxide layer arranged on both sides of the modified two-dimensional titanium carbide layer, and the modified two-dimensional titanium carbide layer is a lapis lazuli modified two-dimensional titanium carbide layer.

[0006] The present application uses the ionic dye lapis lazuli with a conjugated skeleton and strong non-covalent interaction to modify two-dimensional titanium carbide, which is used as a functional layer of a storage device, and the device exhibits a bistable storage behavior; the storage device has ultra-low working voltage, long retention time, and typical bistable electrical switching characteristics; the use of a laminated structure significantly increases the erasability compared with a single-layer structure, and avoids the application limitation problem caused by the low erasability stability of the modified two-dimensional titanium carbide under cyclic voltage scanning.

[0007] Further, the material of the conductive substrate layer is indium tin oxide, platinum, inert metals such as gold, or other conductive materials; and the conductive substrate layer can be arranged on the surface of a glass substrate.

[0008] Further, the metal electrode layer is a metal electrode array, and the material of the metal electrode layer is active metals such as silver and copper.

[0009] The second aspect of the present application provides a preparation method of the above-mentioned surface-engineered two-dimensional titanium carbide memristor, comprising the following steps,

[0010] S1: coating a graphene oxide suspension on the surface of the conductive substrate layer, and vacuum drying to form a first graphene oxide layer;

[0011] S2: coating a mixed solution of two-dimensional titanium carbide and lapis lazuli on the surface of the first graphene oxide layer, and vacuum drying to form a modified two-dimensional titanium carbide layer;

[0012] S3: coating a graphene oxide suspension on the surface of the modified two-dimensional titanium carbide layer, and vacuum drying to form a second graphene oxide layer;

[0013] S4: sputtering a metal electrode layer on the surface of the second graphene oxide layer to obtain the surface-engineered two-dimensional titanium carbide memristor.

[0014] The preparation method of the present application is simple and has high repeatability, and the obtained memristor structure follows a laminated structure of a conductive substrate / three-layer functional film / electrode, wherein the three-layer functional film is a graphene oxide / surface-engineered two-dimensional titanium carbide / graphene oxide laminated structure.

[0015] Furthermore, the concentration of the graphene oxide suspension is 0.8–1.2 mg / mL.

[0016] Furthermore, the graphene oxide suspension is prepared by dispersing graphene oxide in water, and the dispersion method can be ultrasonic dispersion for 1 to 3 hours.

[0017] Furthermore, in the mixture of two-dimensional titanium carbide and celestite blue, the mass ratio of two-dimensional titanium carbide to celestite blue is 20:1 to 1:10; specifically, it can be 20:1, 10:1, 5:1, 1:1, 1:5, 1:10 or any two of these ratios; preferably, the mass ratio is 10:1 to 1:5; more preferably, it is 5:1 to 1:5.

[0018] Furthermore, in the mixture of two-dimensional titanium carbide and azurite blue, the concentration of two-dimensional titanium carbide is 0.1–0.3 mg / mL.

[0019] Specifically, the mixture of two-dimensional titanium carbide and azurite blue can be obtained by mixing a two-dimensional titanium carbide aqueous solution with a concentration of 0.5 mg / mL and an azurite blue aqueous solution with a concentration of 0.05 to 10 mg / mL at a volume ratio of 1:1.

[0020] Furthermore, the two-dimensional titanium carbide is prepared by reacting aluminum carbide powder with hydrofluoric acid solution.

[0021] Furthermore, in steps S1-S3, the coating method is spin coating.

[0022] Furthermore, the spin coating parameters are as follows: first spin coating at a speed of 400-600 rpm for 5-10 seconds, and then spin coating at a speed of 1000-1500 rpm for 15-25 seconds; forming a first graphene oxide layer, a modified two-dimensional titanium carbide layer, or a second graphene oxide layer with a thickness of 100-300 nm.

[0023] Furthermore, in steps S1-S3, the vacuum drying temperature is 60-80℃ and the time is 1-3 hours.

[0024] Furthermore, in step S4, the metal electrode layer is sputtered using a magnetron sputtering device and then sputtered onto the surface of the second graphene oxide layer with the aid of a mask. The pressure inside the sputtering chamber does not exceed 10. -6 mbar, sputtering rate of 3-4 nm / min.

[0025] A third aspect of the present invention provides a data storage device comprising the above-described surface-engineered modified two-dimensional titanium carbide memristor.

[0026] The technical solution of the present invention has the following advantages compared with the prior art:

[0027] 1、 The application solves the problem of conductivity of two-dimensional titanium carbide metal by surface engineering modification, and widens its application in the field of data storage; Specifically, lapis lazuli is used to modify two-dimensional titanium carbide, so that the device exhibits a high resistance state switching ratio;

[0028] 2、 The device adopts a laminated structure strategy to solve the problem of unstable performance of single-layer two-dimensional titanium carbide memristor, and is expected to be applied in the field of storage; Specifically, the graphene oxide layer introduced on the top and bottom of the modified two-dimensional titanium carbide can effectively act as a buffer layer, thereby controlling the ordered formation of conductive filaments during device operation, so that the memristor exhibits stable and reliable erasable characteristics. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A flowchart for preparing two-dimensional titanium carbide solution and lapis lazuli solution of the application.

[0030] Figure 2 (a) Raman and (b) X-ray diffraction patterns of two-dimensional titanium carbide prepared from precursor titanium aluminum carbide of the application.

[0031] Figure 3 Current-voltage performance test graph of two-dimensional titanium carbide and lapis lazuli of the application.

[0032] Figure 4 Atomic force microscope graph (AFM) of two-dimensional titanium carbide film layer of the application.

[0033] Figure 5 Atomic force microscope graph (AFM) of ion type dye lapis lazuli of the application.

[0034] Figure 6 (a) Raman and (b) X-ray diffraction patterns of two-dimensional titanium carbide modified by lapis lazuli of the application.

[0035] Figure 7 Atomic force microscope graph (AFM) of two-dimensional titanium carbide modified by lapis lazuli of the application.

[0036] Figure 8 Silver electrode / modified two-dimensional titanium carbide / indium tin oxide / glass memristor device structure graph under scanning electron microscope (SEM) of the application.

[0037] Figure 9 Memristor characteristic graph of two-dimensional titanium carbide modified by lapis lazuli with different mass concentrations (mass concentration is 0.5 mg / mL) of the application (lapis lazuli:two-dimensional titanium carbide = 20:1, 10:1, 5:1, 1:1, 1:5, 1:10).

[0038] Figure 10 (a) the reproducibility of the memristive performance of the modified two-dimensional titanium carbide of the present application under different conditions and (b) the electrical resistance state stability curve of the modified two-dimensional titanium carbide in the initial state. 4 s).

[0039] Figure 11 Memristive switching mechanism diagrams of the modified two-dimensional titanium carbide of the present application using (a, b) inert electrodes Au and (c, d) active electrodes Ag as electrodes, respectively.

[0040] Figure 12 (a) Raman diagram and (b) electrical performance test diagram of the graphene oxide of the present application.

[0041] Figure 13 Flowchart of preparation of the three-layer functional layer memristor device in the embodiment of the present application.

[0042] Figure 14 Stability diagram of electrical performance of different functional layer structures under a cyclic voltage.

[0043] Figure 15 (a, b) Stability curve test diagram of the modified two-dimensional titanium carbide of the present application using a laminated structure, (c) opening voltage and closing voltage distribution diagram, and (d) current switching ratio distribution diagram.

[0044] Figure 16 (a) the reproducibility of the memristive performance of the modified two-dimensional titanium carbide of the present application under different conditions and (b) the electrical resistance state stability curve of the modified two-dimensional titanium carbide in the initial state. 4 s). DETAILED DESCRIPTION

[0045] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not limiting to the present application.

[0046] Example 1 Preparation of surface-engineered two-dimensional titanium carbide memristor

[0047] Step one, the graphene oxide used in the experiment was prepared by Hummers method. 10 mg of graphene oxide (GO) was dispersed in 10 mL of ionized water to prepare a 1 mg / mL graphene oxide suspension, which was ultrasonicated for 1-3 h and stored for use;

[0048] Step two, titanium aluminum carbide powder (1 g) was added to 10 mL of hydrofluoric acid solution, stirred at 25 °C for 48 h to remove Al, and the obtained two-dimensional titanium carbide product was repeatedly centrifuged and washed with deionized water until the pH value reached about 6.0, and dried in a vacuum drying oven at 60 °C for 24 h. Finally, the obtained two-dimensional titanium carbide powder was weighed by a balance and dispersed in deionized water to prepare a 0.5 mg / mL two-dimensional titanium carbide solution. Celestine blue particles were dissolved in deionized water to prepare six different concentrations of celestine blue solutions (10 mg / mL, 5 mg / mL, 2.5 mg / mL, 0.5 mg / mL, 0.1 mg / mL, 0.05 mg / mL) in turn. The two-dimensional titanium carbide aqueous solution was mixed with the six concentrations of celestine blue solution at a volume ratio of 1:1 to obtain six new mixed solutions, which were filtered by a 0.22 μm PTFE (polytetrafluoroethylene) membrane filter after ultrasonic filtration for 1-3 h to obtain new two-dimensional titanium carbide-celestine blue solutions.

[0049] Step three, preparation of the first graphene oxide layer, the prepared 1 mg / mL graphene oxide suspension was dropped on the indium tin oxide conductive substrate, and spin-coated by a spin coater at a low speed of 500 rpm for 6 s and then at a high speed of 1000 rpm for 20 s. The spin-coated film was placed in a vacuum drying oven and dried at 60-80 °C for 1-3 h under vacuum.

[0050] Step four, preparation of the modified two-dimensional titanium carbide layer, the prepared two-dimensional titanium carbide-celestine blue mixed solution was dropped on the dried graphene oxide film, and spin-coated by a spin coater at a low speed of 500 rpm for 6 s and then at a high speed of 1000 rpm for 20 s. The spin-coated film was again placed in a vacuum drying oven and dried at 60-80 °C for 1-3 h under vacuum.

[0051] Step five, preparation of the second graphene oxide layer, the prepared 1 mg / mL graphene oxide suspension was dropped on the spin-coated and dried two-layer film, and spin-coated by a spin coater at a low speed of 500 rpm for 6 s and then at a high speed of 1000 rpm for 20 s. A layer of graphene oxide film was spin-coated again to form a graphene oxide / modified two-dimensional titanium carbide / graphene oxide laminated structure, which was placed in a vacuum drying oven and dried at 60-80 °C for 1-3 h under vacuum.

[0052] Step six, a silver electrode array was sputtered on the surface of the three-layer graphene oxide / modified two-dimensional titanium carbide / graphene oxide film (functional film layer) by a mask plate with a circular pattern with the aid of a magnetron sputtering instrument. The pressure in the sputtering cavity was 10 -6 mba, and the thickness of the silver electrode was 300 nm. Finally, a vertical laminated structure of the memristor was obtained, and the device size was 2×2 cm 2 .

[0053] Test case

[0054] like Figure 1 As shown, the upper part depicts titanium aluminum carbide etched with hydrofluoric acid to obtain two-dimensional titanium carbide powder, which is then dispersed in deionized water and subjected to laser irradiation to form the Tyndall effect. The lower part shows the preparation method of celestolite blue solution: celestolite blue is dissolved in deionized water to quantitatively prepare celestolite blue solutions of 10 mg / mL, 5 mg / mL, 2.5 mg / mL, 0.5 mg / mL (these concentrations are shown as special examples in optical photographs), 0.1 mg / mL, and 0.05 mg / mL.

[0055] like Figure 2 As shown, the two-dimensional titanium carbide has an accurate structure and very high purity, meeting the material purity requirements for preparing memristors.

[0056] like Figure 3 As shown, two-dimensional titanium carbide exhibits metallic-like conductivity. Celestolite blue molecules show weaker conductivity compared to two-dimensional titanium carbide.

[0057] like Figure 4 As shown, the two-dimensional titanium carbide thin film layer exhibits a uniform and continuous nanocrystalline structure at the microscale.

[0058] like Figure 5 As shown, the surface roughness of the celestite blue film is relatively large (film undulation greater than 500 nm).

[0059] like Figure 6 As shown, (a) laser Raman spectroscopy analysis revealed a redshift in the Raman peak of the modified two-dimensional titanium carbide, with a new Raman peak forming at wavenumber 1378.4. (b) the XRD peak with a circular shape at 2θ = 16.16° (004) of the modified two-dimensional titanium carbide film disappeared. The surface engineering modification of two-dimensional titanium carbide was successfully achieved using azurite blue dye molecules, and the modified material was then processed.

[0060] like Figure 7 As shown in the AFM images, the morphology of the two-dimensional titanium carbide nanosheets modified with celestite blue has changed significantly compared with that before modification. The morphology indicates that the surface of the two-dimensional titanium carbide has been modified.

[0061] like Figure 8 As shown, the thickness of the modified two-dimensional titanium carbide functional layer is approximately 300 nm, as captured by scanning electron microscopy (SEM).

[0062] like Figure 9As shown, different mass concentrations of lapis lazuli blue modified two-dimensional titanium carbide, (a) when lapis lazuli blue: two-dimensional titanium carbide = 20:1, the device mainly exhibits the electrical properties of lapis lazuli blue molecules, (b-d) as the content of lapis lazuli blue decreases, the high and low resistance states of the device are gradually opened, and gradually exhibit clear distinguishable resistance states. (d-f) When MXene gradually dominates, the high and low resistance states of the device tend to close and gradually approach the metal-like conductivity of two-dimensional titanium carbide. From the current-voltage logarithmic graph in the figure (a-f) it can be found that as the concentration ratio of the two approaches 1:1, the I-V resistance switching behavior of the device will also become more and more obvious, and the ON / OFF ratio will also increase continuously. When the concentration mass ratio of the two is 1:1, the resistance switching behavior between voltage and current is most obvious, and at this time the positive ON / OFF ratio is greater than 10 2 .

[0063] As shown in Figure 10 , (a) the modified two-dimensional titanium carbide memristor device can exhibit a typical current-voltage curve at room temperature, and after being stored in a non-encapsulated environment for 6 months, the device can still exhibit a typical current-voltage curve. It is shown that the two-dimensional titanium carbide film modified by lapis lazuli blue overcomes the disadvantage of being easily oxidized by the environment, and then the device is placed on a flat heater at 80℃ for 4-6 hours. The electronic device still works normally at high temperature. (b) The modified two-dimensional titanium carbide has a 10 4 s electrical steady-state retention time, and the current level does not fluctuate significantly over time, and the device exhibits clear distinguishable resistance states.

[0064] As shown in Figure 11 , (a, b) when gold is used as an inert electrode, according to the charge transport model, in the low bias voltage region of 0V-0.4V, the charges are caused by thermal excitation, and the current and voltage obey Ohm's law (slope 1.3). In the range of 0.4V-1V, it corresponds to a typical space charge limited transport process (slope 2.5). (b) When silver is used as the top electrode, the current level becomes larger (1mA→60mA), which indicates that in addition to space charge limited current, there is also a conductive filament in the modified two-dimensional titanium carbide storage device. Under the action of an external electric field, the active electrode Ag is oxidized to Ag + at the anode of the device, Ag + migrates under the electric field and is regenerated as Ag at the cathode through a reduction reaction, and silver particles accumulate to form a conductive filament, which further increases the conductivity and expands the resistance switching ratio of the device.

[0065] As shown in Figure 12 , (a) the structure of graphene oxide is accurate and has very high purity, meeting the material purity requirements for the preparation of memristors. (b) The conductivity of graphene oxide is poor at -2-2V, which may be related to its structural defects.

[0066] As shown in Figure 13 , the preparation process of the layered structure modified two-dimensional titanium carbide memristor, the memristor structure is composed of glass substrate, indium tin oxide, first graphene oxide layer, modified two-dimensional titanium carbide, second graphene oxide layer, and silver metal electrode.

[0067] As shown in Figure 14 , (a) the graphene oxide / modified two-dimensional titanium carbide / graphene oxide memristor of the application can exhibit typical current-voltage curves at room temperature and in a non-encapsulated environment for 6 months, and at 80℃ for 2 hours, respectively; (b) the graphene oxide / modified two-dimensional titanium carbide / graphene oxide has a 10 4 s electrical steady-state retention time in the initial state.

[0068] As shown in Figure 15 , (a) the layered structure modified two-dimensional titanium carbide memristor of the application exhibits a stable current-voltage characteristic curve of 50 cycles under a 1.2V cyclic voltage scan, which provides the possibility for binary storage; (b) a logarithmic graph; (c) the turn-on voltage and turn-off voltage of the layered device under a 50-cycle cyclic voltage scan are Gaussian distributed; (d) the current ON / OFF ratio statistical distribution.

[0069] As shown in Figure 16 , (a) the modified two-dimensional titanium carbide memristor with a layered structure can exhibit typical current-voltage curves at room temperature in a non-encapsulated environment for 6 months and at 80℃ for 2 hours after 6 months, respectively, and the device exhibits excellent reproducibility of the memristive curve; (b) the high and low resistance states of the device are tested for 10 4 s retention time in the original state of the device, and the current level does not fluctuate significantly over time, and the device also exhibits clear and distinguishable resistance states.

[0070] In summary, the surface-engineered two-dimensional titanium carbide memristor based on the layered structure has a simple preparation method, high repeatability, and significantly improved performance stability of the device. The structure of the memory has low operating voltage (about 1V), long retention time (more than 10 4 s), and typical bistable electrical switching characteristics. This work provides a simple method for surface modification of two-dimensional titanium carbide, and broadens the research path of two-dimensional titanium carbide in the field of high-performance non-volatile memory.

[0071] Obviously, the above embodiments are merely example for clearly illustrating, and are not limitation to the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and can not be exhausted. The obvious changes or variations derived therefrom are still within the scope of the present invention.

Claims

1. A surface-engineered modified two-dimensional titanium carbide memristor, characterized in that, The surface engineering modified two-dimensional titanium carbide memristor comprises an electrically conductive substrate layer, a metal electrode layer and a functional film layer arranged between the electrically conductive substrate layer and the metal electrode layer; the functional film layer comprises a modified two-dimensional titanium carbide layer and a graphene oxide layer arranged on both sides of the surface of the modified two-dimensional titanium carbide layer, and the modified two-dimensional titanium carbide layer is a lapis lazuli modified two-dimensional titanium carbide layer.

2. The surface-engineered two-dimensional titanium carbide memristor of claim 1, wherein, The metal electrode layer is a metal electrode array.

3. A method of producing the surface-engineered modified two-dimensional titanium carbide memristor according to claim 1 or 2, characterized in that, The method comprises the following steps, S1: coating an electrically conductive substrate layer with a graphene oxide suspension and vacuum drying to form a first graphene oxide layer; S2: coating the surface of the first graphene oxide layer with a two-dimensional titanium carbide and lapis lazuli mixed solution and vacuum drying to form a modified two-dimensional titanium carbide layer; S3: coating the surface of the modified two-dimensional titanium carbide layer with a graphene oxide suspension and vacuum drying to form a second graphene oxide layer; S4: sputtering a metal electrode layer on the surface of the second graphene oxide layer to obtain the surface engineering modified two-dimensional titanium carbide memristor.

4. The production method according to claim 3, wherein The concentration of the graphene oxide suspension is 0.8-1.2 mg / mL.

5. The production method according to claim 3, wherein In the two-dimensional titanium carbide and lapis lazuli mixed solution, the mass ratio of two-dimensional titanium carbide to lapis lazuli is 20:1-1:10, and the concentration of two-dimensional titanium carbide is 0.1-0.3 mg / mL.

6. The production method according to claim 3, wherein In the steps S1-S3, the coating mode is spin coating.

7. The production method according to claim 6, wherein The spin coating parameters are: first spin coating at a speed of 400-600 rpm for 5-10 s, and then spin coating at a speed of 1000-1500 rpm for 15-25 s.

8. The production method according to claim 3, wherein In the steps S1-S3, the vacuum drying temperature is 60-80℃, and the time is 1-3 h.

9. The production method according to claim 3, wherein In step S4, the metal electrode layer is sputtered by a magnetron sputtering instrument, and is sputtered onto the surface of the second graphene oxide layer by means of a mask plate. The pressure in the sputtering cavity is not higher than 10 mbar, and the sputtering rate is 3-4 nm / min. -6 mbar, and the sputtering rate is 3-4 nm / min.

10. A data storage device, characterized by The surface engineering modified two-dimensional titanium carbide memristor of claim 1 or 2.

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