Analog memristor based on Ga2O3 / TiO2 heterojunction structure and preparation method thereof

Abstract

The invention discloses an analog memristor based on a Ga2O3 / TiO2 heterojunction structure and a preparation method of the analog memristor, and belongs to the field of nonvolatile resistive random access memorizers, the preparation method comprises the following steps: under a vacuum condition, depositing a conductive film on a pretreated insulating substrate by adopting a physical vapor deposition method to serve as a bottom electrode; sequentially depositing a Ga2O3 thin film and a TiO2 thin film on the bottom electrode by adopting a magnetron sputtering method, and constructing a Ga2O3 / TiO2 heterojunction as a resistive layer; and depositing a conductive thin film on the surface of the resistive layer by adopting a physical vapor deposition method to serve as a top electrode to obtain the analog memristor based on the Ga2O3 / TiO2 heterojunction structure. A Ga2O3 semiconductor material with a wide forbidden band and high electron mobility and a TiO2 material with a high dielectric constant, stability and reliability are adopted, and the excellent and high-stability heterojunction memristor is prepared through a specific sputtering process. Bionic behaviors such as synaptic plasticity can be realized, and the method has important application potential in the fields of high-density storage, neural network calculation, biological synaptic simulation and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-volatile resistive random access memory, and particularly relates to a simulation type memristor based on a Ga2O3 / TiO2 heterojunction structure and a preparation method thereof. BACKGROUND

[0002] With the advent of the information age, data information is growing explosively, which puts higher requirements on the processing and storage capacity of computers. In the traditional von Neumann architecture, the computing unit (CPU) and the storage unit (memory) are separated, and the data transmission speed between them limits the overall performance of the computer, that is, the von Neumann bottleneck. Therefore, scientists have proposed a new type of storage technology-memristor, which can realize the integration of storage and calculation of computers, greatly improving the computing power of computers, and is considered to be the most promising non-volatile memory.

[0003] The memristor adopts a simple sandwich structure, which is composed of a top electrode, a resistive layer and a bottom electrode. Its working principle relies on the formation and rupture of conductive filaments. When a stimulating voltage is applied between the top electrode and the bottom electrode, the resistance state of the memristor will change, thereby realizing data storage. The memristor has two resistance states: a high resistance state and a low resistance state. The switching between the two states is realized by the formation and rupture of conductive filaments. This process is mainly realized through ion effect, which involves the migration of oxygen ions or metal ions in an electric field, thereby changing the conductivity of the metal oxide resistive layer. The formation and rupture of conductive filaments in the memristor occur in the metal oxide resistive layer. The formation process of the conductive filament involves the generation and migration of oxygen vacancies. Oxygen vacancies gather to form a conductive filament in a low-voltage state, at which time the current increases and the device is in a low-resistance state. Under the stimulation of a reverse voltage, the oxygen vacancies return to their original positions, the conductive filament breaks, and the device returns to a high-resistance state. The entire process is the basis for the memristor to store information, and data writing and reading are achieved by controlling the current and voltage.

[0004] Gallium oxide has been widely concerned in recent years as a kind of ultra-wide bandgap semiconductor, which belongs to the fourth generation of semiconductor materials. Compared with the third generation of semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN), the bandgap of gallium oxide can reach 4.9 eV. A wider bandgap means that more energy is required for electrons to jump from the valence band to the conduction band. Gallium oxide has excellent properties such as high power, low loss, high temperature and pressure resistance, low hardness and easy processing. In addition, its preparation size is smaller under the same scale, thereby reducing the cost. However, single-layer gallium oxide material as a resistive layer has large power consumption and poor stability. Research shows that using a heterojunction material as a resistive layer material can effectively improve the electrical performance and stability of the memristor. However, there is no report on the preparation of a Ga2O3 / TiO2 heterojunction material as a resistive layer of a simulation memristor device.

[0005] As a new type of non-volatile memory device, the memristor has the advantages of high storage density, low power consumption, low cost, and compatibility with CMOS process, and has broad application prospects in artificial synapse simulation and neuromorphic computing. Its unique resistance change characteristic can effectively simulate the plasticity behavior of biological synapses, providing a hardware foundation for efficient artificial intelligence computing and learning. Compared with traditional computer architecture, the human brain can efficiently process massive information with extremely low power consumption, and this outstanding performance is mainly due to the dynamic adjustable characteristics of neural synapses. In the biological nervous system, the presynaptic neuron acts on the postsynaptic membrane receptor by releasing neurotransmitters, causing changes in the postsynaptic potential, and the connection strength is dynamically adjusted with the neuron activity, showing plasticity behaviors such as long-term potentiation (LTP) and long-term depression (LTD). Studies have shown that the preparation of electronic devices with similar characteristics to biological neural synapses will open up new avenues for the development of the next generation of neuromorphic computing systems. In this context, the analog memristor is the best choice to achieve this goal because it can accurately reproduce the synaptic weight adjustment mechanism, and it is a promising research direction in the field of future information storage technology and artificial intelligence. SUMMARY

[0006] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a Ga2O3 / TiO2 heterojunction structure-based analog memristor and a preparation method thereof, so as to solve the technical problem that the single-layer gallium oxide material as a resistance change layer results in high power consumption and poor stability of the device.

[0007] In order to achieve the above-mentioned purpose, the technical scheme is adopted as follows: The application discloses a preparation method of a Ga2O3 / TiO2 heterojunction structure-based analog memristor, which comprises the following steps: 1) After pretreating an insulating substrate, a conductive thin film is deposited on the pretreated insulating substrate under vacuum conditions by a physical vapor deposition method, serving as a bottom electrode of the analog memristor; 2) A Ga2O3 thin film and a TiO2 thin film are deposited on the bottom electrode prepared in step 1) in sequence by a magnetron sputtering method, so as to construct a Ga2O3 / TiO2 heterojunction, serving as a resistance change layer of the analog memristor; 3) A conductive thin film is deposited on the surface of the resistance change layer prepared in step 2) by a physical vapor deposition method, serving as a top electrode of the analog memristor, so as to obtain the Ga2O3 / TiO2 heterojunction structure-based analog memristor.

[0008] Preferably, in step 1), the pretreatment comprises the following steps: selecting an insulating substrate with high flatness, and sequentially performing ultrasonic cleaning and drying treatment on the insulating substrate by using acetone, deionized water and alcohol; the insulating substrate is transparent glass or a Si substrate, and the ultrasonic cleaning time is 300-900 s.

[0009] Preferably, in step 1), the physical vapor deposition method comprises a magnetron sputtering method or an electron beam evaporation; the conductive film is any one of Pt, Au, W and ITO which is electrochemically inert; and the thickness of the conductive film is 30-300 nm.

[0010] Preferably, in step 2), when the Ga2O3 film is deposited by magnetron sputtering using a Ga2O3 target, the vacuum degree in the chamber is made to reach 8.0*10 -4 During the deposition of the Ga2O3 film, the temperature is 50-250 ℃, and the magnetron sputtering time is 5-20 min.

[0011] Preferably, in step 2), when the Ga2O3 film is deposited by magnetron sputtering, the magnetron sputtering power is 30-150 W, the pressure in the chamber during magnetron sputtering is 0.1-2 Pa, the argon flow rate during magnetron sputtering is 30-60 sccm, and the oxygen flow rate is 5-20 sccm.

[0012] Preferably, in step 2), when the TiO2 film is deposited by magnetron sputtering using a high-purity Ti target, the deposition temperature is 50-250 ℃, and the magnetron sputtering time is 3-15 min.

[0013] Preferably, in step 2), when the TiO2 film is deposited by magnetron sputtering, the magnetron sputtering power is 100-200 W, the pressure in the chamber during magnetron sputtering is 0.1-2 Pa, the argon flow rate during magnetron sputtering is 5-20 sccm, and the oxygen flow rate is 5-20 sccm.

[0014] Preferably, in step 2), the thickness of the Ga2O3 film is 180-720 nm, and the thickness of the TiO2 film is 100-540 nm.

[0015] Preferably, in step 3), the physical vapor deposition method comprises a magnetron sputtering method or an electron beam evaporation; the conductive film is any one of Pt, Au, W and ITO which is electrochemically inert, and the thickness of the conductive film is 30-300 nm; and the top electrode is a circular top electrode with a diameter of 100-300 μm.

[0016] The application further discloses a simulation type memristor based on a Ga2O3 / TiO2 heterojunction structure, which is prepared by the preparation method.

[0017] Compared with the prior art, the application has the following beneficial effects: The application discloses a preparation method of a simulation type memristor based on a Ga2O3 / TiO2 heterojunction structure, selects a binary oxide material titanium oxide and a gallium oxide material to be stacked, the chemical property of the material is stable, the material is resistant to high temperature and oxidation, and the material can exhibit significant resistance change characteristics under the action of an electric field; the heterojunction interface formed by the gallium oxide and the titanium oxide is clear and has high stability, and the simulation type memristor function and the simulation synapse plasticity function can be realized; the substrate material which is simple to obtain, has high flatness, is dry and is pollution-free can make the device more stable when the electrical performance is tested, and the test result is better; the gallium oxide and the titanium oxide heterojunction structure introduces an interface effect, and the device performance is excellent. In the experiment, a magnetron sputtering method is used for thin film growth, the method is easy to operate, the thin film growth speed is fast, the equipment is simple and the method is widely used, the formed thin film surface is uniform, the compactness is good, and the stability is high. Compared with a single gallium oxide memristor, the simulation type memristor prepared by the gallium oxide and the titanium oxide heterojunction has stronger memristor function, realizes fast data reading, realizes multi-level storage, also meets the typical bipolar switching characteristics of the memristor and is compatible with the CMOS semiconductor process, and has significant industrial production and manufacturing potential and wide market application prospect.

[0018] Further, the heterojunction resistance change layer is prepared by using the magnetron sputtering technology, compared with the mechanical peeling method, the shape, size and thickness can be effectively controlled; compared with the chemical vapor deposition, the continuity of the thin film interface is better, and the cost is lower, and the method has the advantages of low cost and high performance; the method can effectively reduce the impurity intervention and improve the thin film quality, and is more suitable for industrial production.

[0019] Further, in the ultrasonic cleaning process, the total cleaning time should be controlled in the range of 300-900 s, if the cleaning time is less than 300 s, the substrate surface is not cleaned, which will significantly affect the quality of the prepared sample; if the cleaning time exceeds 900 s, the substrate may crack, affecting the subsequent preparation and test.

[0020] Further, the sputtering power of the gallium oxide thin film is in the range of 30-150 W, if the power exceeds 150 W, the roughness of the thin film increases significantly, and the stability decreases; and if the power is too low, the thin film growth rate is too slow and the sputtering uniformity is poor. The sputtering time is controlled in the range of 5-20 min, if the time is too long and exceeds 20 min, the thin film thickness is too large, a higher operating voltage is required in the electrical performance test, and the device power consumption is increased; if the time is too short and less than 5 min, the thin film thickness is insufficient, and the device may lose the resistance change characteristics. The deposition temperature is controlled in the range of 50-250 DEG C, if the temperature rises and exceeds 250 DEG C, the simulation type memristor may be converted into a digital type memristor. The argon-oxygen ratio is set to 40:10, since the gallium oxide ceramic target is used, too high oxygen flow will reduce the oxygen vacancy defects in the resistance change layer, and hinder the formation of conductive filaments, therefore, the oxygen flow needs to be strictly controlled.

[0021] Further, the sputtering power of the titanium oxide film is in the range of 100-200 W. Too high power will increase the roughness of the film and reduce stability, and too low power will slow down the growth rate and increase the preparation cost. The sputtering time is set to 3-15 min, and too short time will result in insufficient film thickness, weakening or even disappearing of the resistance change effect; too long time will make the film too thick, significantly increasing the device power consumption during testing. The deposition temperature is in the range of 50-250 DEG C, and too high temperature will increase the roughness and affect the stability, and too low temperature will result in poor film density, causing device performance fluctuations. The argon-oxygen ratio is set to 15:10, and when a high-purity titanium target is used, too low oxygen flow will result in insufficient oxidation of the film, forming excess oxygen vacancy defects, and thus causing the drift of the resistance change parameters and the decrease of the cycle stability.

[0022] The application further discloses the simulation type memristor based on the Ga2O3 / TiO2 heterojunction structure prepared by the preparation method, utilizes the heterojunction formed by gallium oxide and titanium oxide, has unique electronic structure and interface effect, and is a relatively stable simulation type memristor device with continuous change of resistance in a certain range during detection of the electrical performance, and can improve the electrical performance and stability of the gallium oxide device. The simulation type memristor can be applied to the fields of neural network calculation and biological synapses. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 FIG. 1 is a structure schematic diagram of a simulation type resistance change memristor based on a Ga2O3 / TiO2 heterojunction structure prepared by the embodiment 1 of the application; Figure 2 FIG. 2 is a preparation process schematic diagram of a simulation type resistance change memristor based on a Ga2O3 / TiO2 heterojunction structure prepared by the embodiment 1 of the application; Figure 3 FIG. 3 is a logarithmic current-voltage curve diagram of a simulation type resistance change memristor based on a Ga2O3 / TiO2 heterojunction structure prepared by the embodiment 1 of the application; Figure 4 FIG. 4 is a cycle tolerance diagram of a simulation type resistance change memristor based on a Ga2O3 / TiO2 heterojunction structure prepared by the embodiment 1 of the application; Figure 5 FIG. 5 is a retention characteristic diagram of a simulation type resistance change memristor based on a Ga2O3 / TiO2 heterojunction structure prepared by the embodiment 1 of the application; Figure 6 FIG. 6 is a long-term potentiation (LTP) and long-term depression (LTD) diagram of a simulation type resistance change memristor based on a Ga2O3 / TiO2 heterojunction structure prepared by the embodiment 1 of the application. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] In the present application, all the embodiments and preferred embodiments mentioned in the present application can be combined to form new technical solutions, unless otherwise specified.

[0026] In the present application, all the technical features and preferred features mentioned in the present application can be combined to form new technical solutions, unless otherwise specified.

[0027] In the present application, unless otherwise specified, the percentage (%) or part refers to the percentage by weight or weight part of the composition.

[0028] In the present application, unless otherwise specified, each component or its preferred component involved can be combined to form a new technical solution.

[0029] In the present application, unless otherwise specified, the numerical range "a~b" represents a shorthand notation for any real number combination between a and b, where a and b are real numbers. For example, the numerical range "6~22" represents that all real numbers between "6~22" have been listed herein, and "6~22" is only a shorthand notation for these numerical combinations.

[0030] The lower limit and upper limit of the range disclosed in the present application can be one or more lower limits and one or more upper limits, respectively.

[0031] In the present application, the term "and / or" used herein means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0032] In the present application, unless otherwise specified, each reaction or operation step can be performed sequentially or according to the sequence. Preferably, the reaction method herein is performed sequentially.

[0033] Unless otherwise specified, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to that described can also be applied in the present application.

[0034] The present application discloses a preparation method of a simulation type memristor based on Ga2O3 / TiO2 heterojunction structure, and the specific steps are as follows: 1) Select high flatness of insulating substrate transparent glass or Si insulating substrate, ultrasonic cleaning, and drying with air dryer, to get the surface dry and pollution-free insulating substrate; the size of the insulating substrate is 1cm x 1cm, and the ultrasonic cleaning time is 300-900s.

[0035] Preferably, the insulating substrate is single crystal silicon grown with silicon dioxide, and the ultrasonic cleaning uses acetone, deionized water and alcohol in sequence for 300s.

[0036] 2) Put the cleaned insulating substrate into the cavity of the magnetron sputtering, vacuumize the cavity to 8.0x10 - 4 Pa, and deposit a certain thickness of conductive film on the pretreated insulating substrate as the bottom electrode by direct current sputtering method. The conductive film is any one of Pt, Au, W and ITO with electrochemical inertness, and the thickness is 30-300nm.

[0037] Preferably, the bottom electrode used is Pt; the thickness of the bottom electrode is 120nm.

[0038] 3) Replace the radio frequency target material with gallium oxide, and the direct current target material with high-purity titanium target. Stick the corner of the bottom electrode with high-temperature resistant adhesive tape for subsequent electrical test. Sputter a certain thickness of gallium oxide and titanium oxide film on the bottom electrode in sequence by magnetron sputtering method. Adjust the best sputtering temperature, working pressure, argon-oxygen ratio and sputtering power during the sputtering process to obtain Ga2O3 / TiO2 heterojunction. The magnetron sputtering temperature is 50-250℃, and the working pressure is 0.1-2Pa to obtain Ga2O3 / TiO2 heterojunction.

[0039] Fix the sample locally by high-temperature resistant adhesive tape, and keep the bottom electrode contact window to ensure reliable contact for subsequent electrical characterization. When depositing Ga2O3 film by magnetron sputtering, vacuumize the cavity to 8.0x10 -4 Pa, set the sputtering temperature to 50-250℃, and introduce argon gas into the cavity at a flow rate of 30-60sccm and oxygen gas at a flow rate of 5-20sccm. The ignition pressure range is 5-10Pa, the sputtering power is 30-150W, the ignition gallium oxide radio frequency target works at a pressure of 0.1-2Pa, the shutter and shielding disc are opened, and the sputtering time is 5-20min. The thickness of the grown gallium oxide film is 180-720nm. Rotate the sample disc to the titanium target below to prepare the titanium oxide film. Adjust the oxygen flow rate to 5-20sccm, the argon flow rate to 10-40sccm, the substrate temperature to 50-250℃, and the sputtering power to 100-200W. When the working pressure in the cavity is stabilized at 0.1-2Pa, open the titanium target radio frequency sputtering for 3-15min to obtain a TiO2 film with a thickness of 100-540nm.

[0040] Preferably, during the deposition of the Ga2O3 film, the substrate temperature is 100℃, the working pressure is 0.5 Pa, the sputtering power of the gallium oxide film is 100 W, the sputtering time is 10 min, and the thickness of the gallium oxide film is 360 nm. During the growth of the gallium oxide film, the argon flow rate is 40 sccm, and the oxygen flow rate is 10 sccm.

[0041] Preferably, during the deposition of the TiO2 film, the substrate temperature is 100℃, the working pressure is 0.5 Pa, the sputtering power of the titanium oxide film is 150 W, the sputtering time is 7 min, and the thickness of the titanium oxide film is 210 nm. During the growth of the titanium oxide film, the argon flow rate is 15 sccm, and the oxygen flow rate is 10 sccm.

[0042] 4) A mask is placed above the Ga2O3 / TiO2 heterojunction formed by growth, and a top electrode is still grown by the magnetron sputtering method. The sputtering time is 5-20 min, a top electrode is grown, and a simulation type memristor based on a Ga2O3 / TiO2 heterojunction structure is obtained.

[0043] A circular mask is placed above the Ga2O3 / TiO2 heterojunction, the sample is placed in the sputtering chamber, the chamber is evacuated to 8×10 -4 Pa, the argon flow rate is adjusted to 30-60 sccm, the ignition pressure is set to 5-10 Pa, the temperature is room temperature, the radio frequency target for controlling the ignition of the W target is turned on, after the plasma is stabilized, the sputtering power is adjusted to 10-40 W, the working pressure is maintained at 0.1-2 Pa, the sputtering time is controlled to 5-40 min, and finally a circular top electrode with a diameter of 100-300 μm and a thickness of 30-300 nm is formed above the heterojunction.

[0044] Preferably, the conductive film selected for the top electrode is metal tungsten; the diameter of the circular mask is 200 μm, and the thickness of the top electrode is 120 nm.

[0045] The present invention discloses an analog resistive switching memristor based on a Ga2O3 / TiO2 heterojunction structure, fabricated using the aforementioned method. The device comprises, from bottom to top, an insulating substrate, a bottom electrode, a Ga2O3 / TiO2 heterojunction resistive switching layer, and a top electrode. Gallium oxide, as an ultra-wide-bandgap semiconductor material, and titanium oxide both exhibit excellent high-temperature stability and chemical inertness. Their synergistic effect significantly optimizes the device's electrical performance. The resulting memristor offers advantages such as simple processing, low cost, and strong scalability, making it suitable for large-scale integrated circuit manufacturing. Electrical performance testing demonstrates stable resistive switching characteristics at low operating voltages and excellent cycling durability. This low-power, high-performance resistive switching behavior enhances the feasibility of high-density non-volatile random access memory (RRAM) applications. Furthermore, the device exhibits high retention characteristics and uniform switching parameter distribution during continuous scan testing, demonstrating its reliable stability. Based on its biomimetic synaptic properties, including long-term potentiation / depression (LTP / LTD) and spike timing-dependent plasticity (STDP), the device shows important application potential in the fields of neuromorphic computing and brain-like chips.

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] Example 1 A method for preparing an analog resistive memristor based on a Ga2O3 / TiO2 heterojunction structure comprises the following steps: 1) Select a highly flat Si substrate, clean it with acetone, deionized water, and alcohol ultrasonically, and dry it. Then, deposit a 120 nm thick Pt metal layer on the substrate using magnetron sputtering as the bottom electrode of the device. 2) Place high temperature resistant tape on a corner of the bottom electrode, with an area of ​​about 1×1mm 2, put into the vacuum cavity, replace gallium oxide and high-purity titanium target, sputter gallium oxide film and titanium oxide film on the bottom electrode in turn by the magnetron sputtering method, the substrate temperature is heated to 100 DEG C, the working pressure is 0.5 Pa;The flow of argon and oxygen is 40 sccm and 10 sccm in the process of growing gallium oxide film, the sputtering time is 10 min, the sputtering power is 100 W, and the film thickness is 360 nm;The flow of argon and oxygen is 15 sccm and 10 sccm in the process of growing titanium oxide film, the sputtering time is 7 min, the sputtering power is 150 W, and the film thickness is 210 nm;Ga2O3 / TiO2 heterojunction is obtained; 3) A circular mask with a diameter of 200 μm is placed on the Ga2O3 / TiO2 heterojunction, and a metal W with a thickness of 120 nm is deposited on it as the top electrode of the device by magnetron sputtering, thereby obtaining a simulation type memristor based on Ga2O3 / TiO2 heterojunction structure with high stability.

[0048] Please refer to Figure 1 It is a structure schematic diagram of a simulation type resistive switching memristor based on Ga2O3 / TiO2 heterojunction structure prepared by the present application 1. From the figure, it can be seen that the simulation type resistive switching memristor based on Ga2O3 / TiO2 heterojunction structure is sequentially from bottom to top substrate, bottom electrode, resistive switching layer and top electrode, and the resistive switching layer is Ga2O3 / TiO2 heterojunction double-layer structure.

[0049] Please refer to Figure 2 It is a process flow chart of a simulation type resistive switching memristor based on Ga2O3 / TiO2 heterojunction structure prepared by the present application 1. From the figure, it can be seen that the preparation process mainly includes four key steps of substrate selection and cleaning, bottom electrode deposition, Ga2O3 / TiO2 heterojunction growth and top electrode preparation.

[0050] Please refer to Figure 3 It is a logarithmic current-voltage curve diagram of a simulation type resistive switching memristor based on Ga2O3 / TiO2 heterojunction structure prepared by the present application 1. From the figure, it can be seen that in the process of more than 100 continuous direct current cycle scanning, the device can realize highly stable simulation resistive switching behavior through low operating voltage.

[0051] Please refer to Figure 4 It is a cycle endurance characteristic diagram of a simulation type resistive switching memristor based on Ga2O3 / TiO2 heterojunction structure prepared by the present application 1. From the figure, it can be observed that in the 100 cycle tests, the curve does not decrease or increase obviously, and the on-off ratio is maintained above one order of magnitude.

[0052] Please refer to Figure 5A holding characteristic diagram of a Ga2O3 / TiO2 heterojunction structure-based analog resistive switching memristor prepared in Embodiment 1 of the present application is shown in FIG. 1. It can be observed from the diagram that the tested holding time is 10 4 s, the read voltage is 0.05 V, and it is stable continuously within 10000 s.

[0053] Please refer to Figure 6 A long-term potentiation (LTP) and long-term depression (LTD) diagram of a Ga2O3 / TiO2 heterojunction structure-based analog resistive switching memristor prepared in Embodiment 1 of the present application is shown in FIG. 2. It can be observed from the diagram that there is significant synaptic plasticity, which is in line with the analog synaptic resistive switching characteristics and is suitable for prominent weight simulation in neuromorphic computing. The symmetry of the LTP / LTD curve also indicates that the bidirectional regulation performance of the device is good.

[0054] Embodiment 2 A preparation method of a Ga2O3 / TiO2 heterojunction structure-based analog resistive switching memristor, comprising the following steps: 1) A conductive transparent glass with high flatness is selected, and is ultrasonically cleaned with acetone, deionized water and alcohol in sequence and dried, and an ITO film with a thickness of 30 nm is deposited as a bottom electrode of the device by using a magnetron sputtering method; 2) A high-temperature resistant adhesive tape is placed on one corner of the bottom electrode with an area of about 1*1 mm 2 , and is placed into a vacuum chamber, and the gallium oxide and high-purity titanium targets are replaced, and a gallium oxide film and a titanium oxide film are sputtered on the bottom electrode in sequence by using a magnetron sputtering method, the substrate temperature is heated to 100 ℃, and the working pressure is 0.1 Pa; the flow rates of argon and oxygen introduced during the growth of the gallium oxide film are 40 sccm and 10 sccm respectively, the sputtering time is 10 min, the sputtering power is 100 W, and the film thickness is 360 nm; the flow rates of argon and oxygen introduced during the growth of the titanium oxide film are 15 sccm and 10 sccm respectively, the sputtering time is 7 min, the sputtering power is 150 W, and the film thickness is 210 nm; a Ga2O3 / TiO2 heterojunction is obtained. 3) A circular mask with a diameter of 100 μm is placed on the Ga2O3 / TiO2 heterojunction, and an ITO film with a thickness of 30 nm is deposited as a top electrode of the device by using a magnetron sputtering method above it, thereby obtaining an analog memristor based on a Ga2O3 / TiO2 heterojunction structure.

[0055] In Embodiment 2, the indium tin oxide conductive film is used as the bottom electrode of the device, which has a lower material cost than Pt and can be suitable for large-scale production, and in addition, it has a higher light transmittance and can be used for transparent electronic devices or optical synapses and the like applications, but the ITO film used has a smaller thickness, and the device obtained by constructing an analog memristor has poorer resistive switching performance and stability.

[0056] Example 3 A preparation method of a simulation type resistive switching memristor based on a Ga2O3 / TiO2 heterojunction structure, comprising the following steps: 1) Select a high flatness insulating Si substrate, sequentially ultrasonic clean with acetone, deionized water and alcohol and dry, and deposit a metal Au with a thickness of 300 nm on the substrate as a bottom electrode of the device by a magnetron sputtering method; 2) Place a high-temperature-resistant adhesive tape at a corner on the bottom electrode with an area of about 1*1 mm 2 , put it into a vacuum chamber, replace the gallium oxide and high-purity titanium target materials, and sequentially sputter a gallium oxide film and a titanium oxide film on the bottom electrode by a magnetron sputtering method, the substrate temperature is heated to 250 ℃, and the working pressure is 2 Pa; wherein the flow rates of argon and oxygen introduced during the growth of the gallium oxide film are 30 sccm and 5 sccm, the sputtering time is 5 min, the sputtering power is 30 W, and the film thickness is 180 nm; the flow rates of argon and oxygen introduced during the growth of the titanium oxide film are 10 sccm and 5 sccm, the sputtering time is 3 min, the sputtering power is 100 W, and the film thickness is 100 nm; a Ga2O3 / TiO2 heterojunction is obtained. 3) Place a circular mask with a diameter of 300 μm on the Ga2O3 / TiO2 heterojunction, and deposit a metal Au with a thickness of 300 nm on the top as a top electrode of the device by a magnetron sputtering method, thereby obtaining a simulation type resistive switching memristor based on a Ga2O3 / TiO2 heterojunction structure with high stability.

[0057] In Example 3, the Ga2O3 / TiO2 heterojunction used in the growth process is compared with Example 1, the temperature is changed, and the deposition temperature is set to 250 ℃. The device shows a sudden process in the set and reset processes, which helps to be applied in the storage field. The film thickness of the bottom electrode and the top electrode is large, which significantly affects the conductive performance of the device.

[0058] Example 4 A preparation method of a simulation type resistive switching memristor based on a Ga2O3 / TiO2 heterojunction structure, comprising the following steps: 1) Select a high flatness insulating Si substrate, sequentially ultrasonic clean with acetone, deionized water and alcohol and dry, and deposit a metal W with a thickness of 120 nm on the substrate as a bottom electrode of the device by a magnetron sputtering method; 2) Place a high-temperature-resistant adhesive tape at a corner on the bottom electrode with an area of about 1*1 mm 2, put into the vacuum chamber, replace the gallium oxide and high-purity titanium target, sputter gallium oxide film and titanium oxide film on the bottom electrode in turn by magnetron sputtering method, the substrate temperature is heated to 50 ℃, the working pressure is kept at 0.5 Pa; wherein the flow rate of argon and oxygen introduced during the growth of gallium oxide film is 60 sccm and 20 sccm, the sputtering time is 20 min, the sputtering power is 150 W, and the film thickness is 720 nm; the flow rate of argon and oxygen introduced during the growth of titanium oxide film is 40 sccm and 20 sccm, the sputtering time is 15 min, the sputtering power is 150 W, and the film thickness is 540 nm; Ga2O3 / TiO2 heterojunction is obtained; 3) A circular mask with a diameter of 200 μm is placed on the Ga2O3 / TiO2 heterojunction, and a metal Pt with a thickness of 120 nm is deposited on it as the top electrode of the device by magnetron sputtering method, thereby obtaining a simulation type memristor based on Ga2O3 / TiO2 heterojunction structure with high stability.

[0059] In Example 4, the gallium oxide film in the resistive switching layer of the prepared device has a large thickness, which significantly affects the electrical performance of the device and makes it worse.

[0060] Example 5 A preparation method of a simulation type resistive switching memristor based on Ga2O3 / TiO2 heterojunction structure, comprising the following steps: 1) Select a high flatness insulating Si substrate, ultrasonic clean it with acetone, deionized water and alcohol in turn and dry it, and deposit a metal Pt with a thickness of 150 nm on the substrate as the bottom electrode of the device by magnetron sputtering method; 2) Place a high-temperature resistant adhesive tape on one corner of the bottom electrode, with an area of about 1×1mm 2 , put into the vacuum chamber, replace the gallium oxide and high-purity titanium target, sputter gallium oxide film and titanium oxide film on the bottom electrode in turn by magnetron sputtering method, the substrate temperature is heated to 50 ℃, the working pressure is kept at 0.5 Pa; wherein the flow rate of argon and oxygen introduced during the growth of gallium oxide film is 60 sccm and 20 sccm, the sputtering time is 20 min, the sputtering power is 150 W, and the film thickness is 720 nm; the flow rate of argon and oxygen introduced during the growth of titanium oxide film is 40 sccm and 20 sccm, the sputtering time is 15 min, the sputtering power is 150 W, and the film thickness is 540 nm; Ga2O3 / TiO2 heterojunction is obtained; 3) A circular mask with a diameter of 200 μm is placed on the Ga2O3 / TiO2 heterojunction, and a metal Pt with a thickness of 120 nm is deposited on it as the top electrode of the device by magnetron sputtering method, thereby obtaining a simulation type resistive switching memristor based on Ga2O3 / TiO2 heterojunction structure.

[0061] In Example 5, the thin film sputtering time is 13 min when depositing the gallium oxide film and 10 min when depositing the titanium oxide film. Compared with Example 1, the thin film sputtering time is prolonged, the thickness of the grown film is increased, the operating voltage is relatively large when testing the electrical properties of the device, which leads to an increase in power consumption, and the stability is poor.

[0062] Example 6 A preparation method of a simulation type resistive switching memristor based on a Ga2O3 / TiO2 heterojunction structure, comprising the following steps: 1) Select a high flatness insulating Si substrate, ultrasonically clean it with acetone, deionized water and alcohol in sequence and dry it, and use electron beam evaporation to grow a metal Pt bottom electrode with a thickness of 120 nm on the substrate; 2) Place a high-temperature-resistant adhesive tape on one corner of the bottom electrode with an area of about 1*1 mm 2 , and sputter a gallium oxide film and a titanium oxide film on the bottom electrode in sequence at a working pressure of 0.5 Pa; wherein the flow rates of argon and oxygen introduced during the growth of the gallium oxide film are 40 sccm and 10 sccm, the substrate temperature is heated to 250 ℃, the sputtering time is 10 min, the power is kept at 100 W, and the film thickness is 360 nm; the flow rates of argon and oxygen introduced during the growth of the titanium oxide film are 15 sccm and 10 sccm, the growth temperature is 100 ℃, the growth time is 7 min, the power is kept at 150 W, and the film thickness is 210 nm; a Ga2O3 / TiO2 heterojunction is obtained. 3) Place a circular mask with a diameter of 100 μm on the Ga2O3 / TiO2 heterojunction, and use electron beam evaporation to obtain a metal W top electrode with a thickness of 120 nm as the device, thereby obtaining a simulation type resistive switching memristor based on a Ga2O3 / TiO2 heterojunction structure.

[0063] In Example 6, the gallium oxide film is heated at the upper limit of its range, and the temperature is too high, which may cause the device to change from a simulation type to a sudden change type.

[0064] In summary, the application discloses a simulation type resistive switching memristor based on a Ga2O3 / TiO2 heterojunction structure and a preparation method thereof, selects an insulating substrate with high flatness, uses a magnetron sputtering method to deposit a bottom electrode, a Ga2O3 / TiO2 heterojunction resistive switching layer and a top electrode on the substrate in sequence, and constructs a sandwich structure resistive switching device. The simulation type memristor based on the Ga2O3 / TiO2 heterojunction structure is obtained. The application uses Ga2O3 semiconductor material with wide band gap and high electron mobility and TiO2 material with high dielectric constant and stable reliability, and prepares a heterojunction memristor through a specific sputtering process. The preparation method is simple, and the cost is low. The Ga2O3 / TiO2 heterojunction structure formed by gallium oxide and titanium oxide has good interface effect, and the oxygen vacancy distribution can realize the formation and breaking process of continuous and gradual conductive filaments. The simulation memristor has excellent and stable performance, can realize bionic behaviors such as synaptic plasticity, and has important application potential in the fields of high-density storage, neural network calculation and biological synapse simulation. In the electrical performance test, the device shows stable and excellent simulation type resistive switching characteristics. The gradual change characteristics of the device have broad prospects in the fields of simulation synaptic weight and neural network calculation.

[0065] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A method for preparing an analog memristor based on a Ga2O3 / TiO2 heterojunction structure, characterized in that: include: 1) After pre-treating the insulating substrate, a conductive film is deposited on the pre-treated insulating substrate using a physical vapor deposition method under vacuum conditions to serve as the bottom electrode of the analog memristor; 2) Using magnetron sputtering, a Ga2O3 film and a TiO2 film are sequentially deposited on the bottom electrode prepared in step 1) to construct a Ga2O3 / TiO2 heterojunction as the resistive switching layer of the analog memristor; 3) A conductive film is deposited on the surface of the resistive layer prepared in step 2) by physical vapor deposition as a top electrode of the analog memristor, thereby obtaining an analog memristor based on a Ga2O3 / TiO2 heterojunction structure.

2. The method for preparing an analog memristor based on a Ga2O3 / TiO2 heterojunction structure according to claim 1, wherein: In step 1), the pretreatment includes: selecting an insulating substrate with high flatness, ultrasonically cleaning it with acetone, deionized water, and alcohol, and drying it in sequence; the insulating substrate is a transparent glass or Si substrate, and the ultrasonic cleaning time is 300 to 900 seconds.

3. The method for preparing an analog memristor based on a Ga2O3 / TiO2 heterojunction structure according to claim 1, wherein: In step 1), the physical vapor deposition method includes magnetron sputtering or electron beam evaporation; the conductive film is any one of Pt, Au, W and ITO with electrochemical inertness; and the thickness of the conductive film is 30-300 nm.

4. The method for preparing an analog memristor based on a Ga2O3 / TiO2 heterojunction structure according to claim 1, wherein: In step 2), when Ga2O3 target material is used for magnetron sputtering deposition of Ga2O3 thin film, the vacuum degree in the chamber is set to 8.0×10 -4 Pa, during the deposition of Ga2O3 thin films, the temperature is 50~250 ℃, and the magnetron sputtering time is 5~20min.

5. The method for preparing an analog memristor based on a Ga2O3 / TiO2 heterojunction structure according to claim 1, wherein: In step 2), when depositing the Ga2O3 film by magnetron sputtering, the power of the magnetron sputtering is 30~150 W, the pressure in the chamber during magnetron sputtering is 0.1~2 Pa, the argon flow rate during magnetron sputtering is 30~60 sccm, and the oxygen flow rate is 5~20 sccm.

6. The method for preparing an analog memristor based on a Ga2O3 / TiO2 heterojunction structure according to claim 1, wherein: In step 2), when a high-purity Ti target is used for magnetron sputtering deposition of TiO2 thin film, the deposition temperature is 50-250°C, and the magnetron sputtering time is 3-15 min.

7. The method for preparing an analog memristor based on a Ga2O3 / TiO2 heterojunction structure according to claim 1, characterized in that: In step 2), when the TiO2 thin film is deposited by magnetron sputtering, the power of the magnetron sputtering is 100~200 W, the pressure in the chamber during magnetron sputtering is 0.1~2 Pa, the argon flow rate during the magnetron sputtering process is 5~20 sccm, and the oxygen flow rate is 5~20 sccm.

8. The method for preparing an analog memristor based on a Ga2O3 / TiO2 heterojunction structure according to claim 1, wherein: In step 2), the thickness of the Ga2O3 film is 180-720 nm; the thickness of the TiO2 film is 100-540 nm.

9. The method for preparing an analog memristor based on a Ga2O3 / TiO2 heterojunction structure according to claim 1, wherein: In step 3), the physical vapor deposition method includes magnetron sputtering or electron beam evaporation; the conductive film is any one of Pt, Au, W and ITO with electrochemical inertness, and the thickness of the conductive film is 30-300 nm; the top electrode is a circular top electrode with a diameter of 100-300 μm.

10. An analog memristor based on a Ga2O3 / TiO2 heterojunction structure, characterized in that: The analog memristor based on the Ga2O3 / TiO2 heterojunction structure comprises, from bottom to top, an insulating substrate, a bottom electrode, a resistive switching layer and a top electrode; the resistive switching layer is a Ga2O3 / TiO2 heterojunction.

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