Heterojunction memristor based on two-dimensional material CrPS4 and preparation method thereof

Abstract

The invention provides a heterojunction memristor based on a two-dimensional material CrPS4 and a preparation method of the heterojunction memristor, and relates to the field of microelectronic semiconductor material photoelectric memristors. The heterojunction memristor comprises a substrate, a two-dimensional material CrPS4-based heterojunction and an active metal electrode which are stacked in sequence. According to the vertical heterojunction memristor disclosed by the invention, the prepared novel two-dimensional material CrPS4 is adopted as a resistive function layer material, and the vertical heterojunction memristor shows excellent non-volatile resistive property.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic memristors of microelectronic semiconductor materials, and particularly to a heterojunction memristor based on two-dimensional material CrPS4 and a preparation method thereof. Background Art

[0002] A memristor is a novel passive circuit element, different from traditional resistors, capacitors, and inductors. Its uniqueness lies in that its resistance value can be dynamically adjusted according to the voltage passing through it and can maintain this changed state to a certain extent, showing a memory effect. In view of the high-speed computing ability, low power consumption characteristics, easy integration, simple structure, and compatibility with CMOS circuits of memristors, in recent years, it has become the focus in many research fields such as non-volatile storage technology, logic operation, and neuromorphic computing similar to the brain. The structure of a memristor is generally a typical metal-functional layer-metal sandwich structure, including a planar structure and a vertical structure, which has a great similarity with the structure of a synapse. The two electrodes can be regarded as the presynaptic membrane and the postsynaptic membrane respectively, and the middle functional layer or dielectric layer corresponds to the synaptic cleft, where the movement of metal ions and neurotransmitters has the same meaning. Currently, memristors of various transition metal oxides such as TaO x , HfO x , TiO x etc. have been widely studied and commercially used. These devices have a metal / TMO / metal structure and exhibit memristive phenomena through the movement of atomic-level elements such as metal ions and vacancies, and then are precisely controlled, resulting in multi-state resistance changes to achieve synaptic functions. However, when the size of the device is reduced to the nanoscale, challenges such as increased leakage current and difficulty in achieving bending will be encountered, which limits the further improvement of the integration degree.

[0003] Since the successful preparation of graphene, two-dimensional materials have gradually attracted extensive attention of researchers, opening up a new path for the development of miniaturized, high-performance, and flexible transparent memristors. With their excellent flexibility, atomic-level thickness, and diverse material selection, two-dimensional materials show great application prospects as memristive functional layers. Currently, although research on memristors based on two-dimensional materials (such as transition metal dichalcogenides MoS2, WS2, WSe2, etc.) has made progress, problems such as insufficient on / off ratio, poor durability, and high power consumption still exist. Summary of the Invention

[0004] The main technical problem to be solved by the present invention is to simplify the preparation process, improve the durability and on / off ratio of the device, effectively reduce the energy consumption, and at the same time maintain the high performance and good compatibility with CMOS technology of the memristor by forming a heterojunction structure using CrPS4 and other two-dimensional materials.

[0005] To solve the above technical problems, the technical solution provided by the present invention is as follows:

[0006] A heterojunction memristor based on two-dimensional material CrPS4, comprising a substrate, a two-dimensional material CrPS4-based heterojunction, and an active metal electrode stacked in sequence.

[0007] Optionally, the two-dimensional material CrPS4-based heterojunction includes:

[0008] A layer of two-dimensional material CrPS4 as a resistive switching functional layer;

[0009] At least one layer of other two-dimensional material layer, and the other two-dimensional material is selected from one of MoS2, Graphene, BP, WS2, and MoSe2;

[0010] The resistive switching functional layer and the other two-dimensional material layer form a vertical stacking structure.

[0011] Optionally, the thickness of the resistive switching functional layer and the other two-dimensional material layer is 10 - 300 nm.

[0012] Optionally, there are two active metal electrodes;

[0013] The two active metal electrodes are respectively disposed on the resistive switching functional layer and the other two-dimensional material layer.

[0014] Optionally, the active metal electrode is a strip-shaped parallel electrode;

[0015] The active metal electrode is arranged perpendicular to the direction of the two-dimensional material CrPS4-based heterojunction and extends from one end to the other end of the two-dimensional material CrPS4-based heterojunction.

[0016] Optionally, the distance between the two active metal electrodes is 2 - 20 μm.

[0017] Optionally, the thickness of the active metal electrode is 50 - 300 nm.

[0018] Optionally, the active metal electrode is made of Ag, Cu, Ti, Ni, or Al.

[0019] Optionally, the substrate includes a composite substrate composed of a single-crystalline silicon substrate and a silicon dioxide layer formed on its surface.

[0020] Optionally, the thickness of the single-crystalline silicon substrate is 500 μm, and the thickness of the silicon dioxide layer is 280 - 300 nm.

[0021] Optionally, the single-crystalline silicon substrate is a highly doped P-type silicon with a resistivity of 0.001 - 0.005 Ω·cm.

[0022] A preparation method of a heterojunction memristor based on two-dimensional material CrPS4, comprising the following steps: Substrate pretreatment: Immerse the substrate in acetone, ethanol, and deionized water in sequence for ultrasonic cleaning, and blow dry with nitrogen after cleaning;

[0023] Exfoliation and transfer of two-dimensional materials: Fold and tear CrPS4 and another two-dimensional material repeatedly with tape until speckled thin layers are obtained, transfer the two speckled thin layers to the surface of polydimethylsiloxane, and tear off the tape after heating to complete mechanical exfoliation;

[0024] Heterostructure construction: Vertically stack the CrPS4 layer on the dimethylsiloxane and another two-dimensional material layer under a microscope to form a heterojunction, where the CrPS4 layer serves as the resistive switching functional layer;

[0025] Electrode preparation: Define the electrode pattern in the overlapping area of the heterojunction through photolithography process and evaporate the active metal to form the top electrode, and the top electrode is in contact with the CrPS4 layer and another two-dimensional material layer respectively to form a heterojunction memristor with a vertical structure.

[0026] Optionally, the vacuum degree of evaporation is lower than 10 -4 Pa.

[0027] The technical solution provided by the present invention has the following technical effects:

[0028] 1. The growth method of the resistive switching functional layer material CrPS4 required by the present invention adopts the chemical vapor transport method, which is easy for batch production and reduces the preparation cost of the device.

[0029] 2. The vertical heterojunction memristor and its preparation method of the present invention use the pre-prepared novel two-dimensional material CrPS4 as the resistive switching functional layer material. After testing, it shows excellent non-volatile resistive switching performance. The switching ratio of the Graphene-CrPS4 heterojunction is as high as 10 8 , the light-free startup voltage is 0.2V, and only 0.15V (low power consumption) is required when adding red light to the MoS2-CrPS4 heterojunction. The device has good cycle durability (up to 150 times) and good time retention characteristics (up to 105s). CrPS4 as the resistive switching functional layer material expands the selection range of the resistive switching layer material, and uses the active metal as the top electrode of the device, and greatly improves the turn-on speed of the memristor by using the principle of electrochemical active ion migration.

[0030] 3. The heterojunction material in the present invention is directly prepared in-situ by a fully dry mechanical transfer on a silicon / silicon dioxide layer substrate. The method is simple, can obtain a cleaner interface, and reduces the preparation difficulty. Description of the drawings

[0031] The above and other features and advantages of the present invention will become more apparent by describing in detail its exemplary embodiments with reference to the accompanying drawings.

[0032] Figure 1 It is a schematic structural diagram of a heterojunction memristor based on two-dimensional material CrPS4 provided in an embodiment of the present invention;

[0033] Figure 2 It is a schematic diagram of the full dry transfer process in an embodiment of the present invention;

[0034] Figure 3a A micrograph of the Graphene-CrPS4 heterojunction memristor device in an embodiment of the present invention;

[0035] Figure 3b A micrograph of the MoS2-CrPS4 heterojunction memristor device in an embodiment of the present invention;

[0036] Figure 4a A Set curve graph of cyclic scanning of the MoS2-CrPS4 heterojunction memristor in an embodiment of the present invention under a lightless environment;

[0037] Figure 4b An I-V curve graph of cyclic scanning of the MoS2-CrPS4 heterojunction memristor in an embodiment of the present invention under a lighted environment;

[0038] Figure 5a A Set curve graph of cyclic scanning of the Graphene-CrPS4 heterojunction memristor of the present invention;

[0039] Figure 5b An I-V curve graph of cyclic scanning of the Graphene-CrPS4 heterojunction memristor of the present invention;

[0040] Figure 6a A logarithmic graph of the I-V curve of cyclic scanning of the Graphene-CrPS4 heterojunction memristor of the present invention under a lightless environment;

[0041] Figure 6b A logarithmic graph of the I-V curve of cyclic scanning of the MoS2-CrPS4 heterojunction memristor of the present invention under a lightless environment;

[0042] Figure 7 A durability test graph of the Graphene-CrPS4 heterojunction memristor of the present invention;

[0043] Figure 8 It is a flowchart of a preparation method of a heterojunction memristor based on two-dimensional material CrPS4 provided in an embodiment of the present invention.

[0044] Explanation of reference numerals:

[0045] 1. Substrate, 2. Two-dimensional material CrPS4-based heterojunction, 3. Active metal electrode;

[0046] 11. Monocrystalline silicon substrate, 12. Silicon dioxide layer;

[0047] 21. Resistive switching functional layer, 22. Other two-dimensional material layer. Detailed implementation manners

[0048] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote the same or similar structures, and thus their detailed description will be omitted.

[0049] The terms "a", "an", "the", and "said" are used to denote the presence of one or more elements / components / etc.; the terms "comprising" and "having" are used to mean an open inclusion and mean that there may be additional elements / components / etc. in addition to the listed elements / components / etc.

[0050] Figure 1 is a schematic structural diagram of an active protection type guardrail provided in an embodiment of the present invention; Figure 2 is a schematic structural diagram of removing the storage box and the flip cover of an active protection type guardrail provided in an embodiment of the present invention; FIG. 3 is a schematic structural diagram of a first perspective view after the active protection type guardrail provided in an embodiment of the present invention is unfolded; FIG. 4 is a schematic structural diagram of a second perspective view after the active protection type guardrail provided in an embodiment of the present invention is unfolded. The above schematic diagrams only show the structural relationship related to the inventive points and do not represent the actual ratio of the actual product.

[0051] Example 1

[0052] As Figures 1 to 7 shown, a heterojunction memristor based on two-dimensional material CrPS4 in this embodiment includes: a substrate 1, a two-dimensional material CrPS4-based heterojunction 2, and an active metal electrode 3 stacked in sequence.

[0053] Among them, the two-dimensional material CrPS4-based heterojunction 2 includes:

[0054] A layer of two-dimensional material CrPS4 as the resistive switching functional layer 21;

[0055] At least one layer of other two-dimensional material layer 22, and the other two-dimensional material is selected from one of MoS2, Graphene, BP, WS2, and MoSe2;

[0056] The resistive switching functional layer 21 and other two-dimensional material layers 22 form a vertical stacking structure.

[0057] The substrate 1 is composed of a single-crystalline silicon substrate 11 and a silicon dioxide layer 12 formed on its surface. Among them, the thickness of the single-crystalline silicon substrate 11 is about 500 μm, and high-doped P-type silicon with a resistivity preferably between 0.001 and 0.005 Ω·cm is selected; the thickness of the silicon dioxide layer 12 is controlled between 280 and 300 nm.

[0058] Two-dimensional material CrPS4-based heterojunction 2:

[0059] Resistive switching functional layer 21: A layer of two-dimensional material CrPS4 with a thickness of 10 to 300 nm is used. This layer, as the core part of the memristor, is responsible for realizing the change of the resistance state.

[0060] Other two-dimensional material layers 22: At least include one layer of other two-dimensional materials, and these materials can be selected from MoS2, Graphene, BP, WS2, MoSe2. The two-dimensional materials form a vertical stacking structure with the CrPS4 layer, and also have a thickness range of 10 to 300 nm. By combining different two-dimensional materials, the device performance can be optimized, such as improving the switching ratio or reducing the power consumption, etc.

[0061] Active metal electrodes 3: Made of metal materials such as Ag, Cu, Ti, Ni, or Al, specifically manifested as two strip-shaped parallel electrodes. These electrodes are arranged perpendicular to the direction of the two-dimensional material CrPS4-based heterojunction 2, extending from one end to the other end. The distance between the two electrodes is set to 2 to 20 μm, and the electrode thickness is 50 to 300 nm. One of the electrodes is connected to the CrPS4 layer, and the other is connected to another two-dimensional material, forming a complete circuit path.

[0062] Example two

[0063] As Figure 8 shown, a preparation method of a heterojunction memristor based on two-dimensional material CrPS4 includes the following steps:

[0064] Step S1: Substrate 1 pretreatment: The substrate 1 is successively immersed in acetone, ethanol, and deionized water for ultrasonic cleaning, and after cleaning, it is dried with nitrogen.

[0065] Select a silicon / silicon dioxide wafer with a size of about 1 cm × 1 cm as the substrate 1. The substrate 1 is successively immersed in acetone, ethanol, and deionized water, and ultrasonic cleaning is carried out for 15 minutes each time to ensure that the surface of the substrate 1 is clean and free of dirt. After cleaning, the substrate 1 is soaked in absolute ethanol for storage. When in use, it only needs to be dried with nitrogen.

[0066] Preferred parameters:

[0067] The purity of acetone, absolute ethanol, and deionized water should be greater than 99.9%.

[0068] The ultrasonic power is 50 W to 100 W.

[0069] Step S2: Two-dimensional material exfoliation and transfer: CrPS4 and another two-dimensional material are respectively torn by repeatedly folding and unfolding the tape until a speckled thin layer is obtained. The two speckled thin layers are transferred to the surface of polydimethylsiloxane, and after heating, the tape is torn off to complete mechanical exfoliation.

[0070] Specifically, CrPS4 and another two-dimensional material (such as MoS2 or Graphene) are respectively placed on the tape of 3M Company in the United States. Through the process of repeatedly folding and tearing the tape until a speckled thin layer is obtained. Then, these tapes are adhered to polydimethylsiloxane (PDMS), and the tape is torn off in one direction to complete the mechanical exfoliation process.

[0071] Preferred parameters:

[0072] The number of times of folding and tearing the tape ranges from 2 to 30 times.

[0073] The thickness of PDMS should be between 0.5 and 3 mm, the heating temperature is maintained at 90 to 120 °C, the time is 2.5 minutes, and then it is left to stand and cool for 3 minutes.

[0074] Step S3: Heterostructure construction: Under the microscope, the CrPS4 layer on the dimethylsiloxane is vertically stacked with another two-dimensional material layer to form a heterojunction, where the CrPS4 layer serves as the resistive switching functional layer 21.

[0075] Under the microscope, samples with consistent and regular geometric shapes and thicknesses are found, and the three-dimensional micro-displacement platform is operated to lap two different materials on the PDMS together to form a vertically stacked heterojunction. Among them, the CrPS4 layer serving as the resistive switching functional layer 21 is located above another two-dimensional material (such as MoS2 or Graphene).

[0076] Specific details:

[0077] The thicknesses of materials such as CrPS4, Graphene, and MoS2 should be controlled within the range of 10 to 300 nm.

[0078] The PDMS is cut into a rectangular block with a size of 1 cm × 1 cm and pressed flat on the surface of the two-dimensional material, and left to stand for a period of time (preferably 2 minutes) to enhance the adhesion force.

[0079] Step S4: Electrode preparation: The electrode pattern is defined in the overlapping area of the heterojunction through photolithography technology, and the active metal is evaporated to form the top electrode. The top electrode is in contact with the CrPS4 layer and another two-dimensional material layer respectively to form a heterojunction memristor with a vertical structure.

[0080] A photolithography process is used to define parallel electrode patterns penetrating the sample. Specifically, it includes the following steps:

[0081] Spin coating: Use a spin coater to spin coat the photoresist evenly on the sample. The rotation speed has a low-speed gear (300 - 600 r / min) and a high-speed gear (3000 - 10000 r / min), and the time is 5 - 20 seconds and 30 - 80 seconds respectively.

[0082] Exposure: Use an ultraviolet exposure machine for photolithography. After exposure, heat the sample for 1 minute (temperature is 100 °C).

[0083] Development: Put the exposed sample into the developer to remove the unexposed photoresist. The development time is controlled within 8 - 10 seconds. After development, place it in deionized water and let it stand for 40 seconds, and finally dry it with high-purity nitrogen.

[0084] Evaporation coating: Use thermal evaporation technology to deposit an active metal (such as Ag) with a thickness of 70 - 100 nm, and the deposition rate is maintained at The vacuum degree is controlled below 10^-4 Pa.

[0085] Etching: Use acetone to etch the photoresist to expose the parallel electrodes of the emitting sample.

[0086] Step S5: Testing and verification

[0087] Use a semiconductor parameter analyzer to conduct electrical tests on the prepared heterojunction memristor and evaluate its current-voltage (I-V) characteristic curve. The test results show that the heterojunction memristor based on CrPS4 exhibits excellent non-volatile resistive switching performance, with a switching ratio as high as 10 8 , a low startup voltage, good cycle stability, and can withstand up to 150 cycle operations.

[0088] In the embodiments of the present invention, the term "a plurality of" refers to two or more, unless otherwise clearly defined. Terms such as "mounted", "connected", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0089] In the description of the embodiments of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the embodiments of the present invention.

[0090] In the description of this specification, the description of terms such as "an embodiment" and "a preferred embodiment" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0091] The above are only the preferred embodiments of the embodiments of the present invention and are not used to limit the embodiments of the present invention. For those skilled in the art, various changes and modifications can be made to the embodiments of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present invention shall be included within the protection scope of the embodiments of the present invention.

Claims

1. A heterojunction memristor based on two-dimensional material CrPS4, characterized in that, Including: A substrate (1), a two-dimensional material CrPS4-based heterojunction (2), and an active metal electrode (3) stacked in sequence.

2. The heterojunction memristor based on two-dimensional material CrPS4 according to claim 1, characterized in that, The two-dimensional material CrPS4-based heterojunction (2) includes: A layer of two-dimensional material CrPS4 as a resistive switching functional layer (21); At least one layer of other two-dimensional material layer (22), and the other two-dimensional material is selected from one of MoS2, Graphene, BP, WS2, and MoSe2; The resistive switching functional layer (21) and the other two-dimensional material layer (22) form a vertical stacking structure.

3. The heterojunction memristor based on two-dimensional material CrPS4 according to claim 2, wherein The thicknesses of both the resistive switching functional layer (21) and the other two-dimensional material layer (22) are 10 - 300 nm.

4. The heterojunction memristor based on two-dimensional material CrPS4 according to claim 3, characterized in that, There are two active metal electrodes (3); The two active metal electrodes (3) are respectively disposed on the resistive switching functional layer (21) and the other two-dimensional material layer (22); The active metal electrode (3) is made of Ag, Cu, Ti, Ni, or Al.

5. The heterojunction memristor based on two-dimensional material CrPS4 according to claim 4, characterized in that, The active metal electrode (3) is a strip-shaped parallel electrode; The active metal electrode (3) is arranged perpendicular to the direction of the two-dimensional material CrPS4-based heterojunction (2), and extends from one end of the two-dimensional material CrPS4-based heterojunction (2) to the other end.

6. The heterojunction memristor based on two-dimensional material CrPS4 according to claim 4 or 5, characterized in that, The distance between the two active metal electrodes (3) is 2 - 20 μm.

7. A heterojunction memristor based on two-dimensional material CrPS4 according to claim 4 or 5, characterized in that, The thickness of the active metal electrode (3) is 50 - 300 nm.

8. The heterojunction memristor based on two-dimensional material CrPS4 according to claim 1, characterized in that, The substrate (1) includes a composite substrate composed of a single-crystalline silicon substrate (11) and a silicon dioxide layer (12) formed on its surface.

9. The heterojunction memristor based on two-dimensional material CrPS4 according to claim 8, wherein, The single-crystalline silicon substrate (11) is a highly doped P-type silicon with a resistivity of 0.001 - 0.005 Ω·cm.

10. A preparation method of a heterojunction memristor based on two-dimensional material CrPS4, characterized in that, Including the following steps: Substrate pretreatment: Immerse the substrate in acetone, ethanol, and deionized water in sequence for ultrasonic cleaning, and blow dry with nitrogen after cleaning; Two-dimensional material peeling and transfer: Fold and tear CrPS4 and another two-dimensional material with tape repeatedly until a spotted thin layer is obtained, transfer the two spotted thin layers to the surface of polydimethylsiloxane, and complete mechanical peeling by tearing off the tape after heating; Heterostructure construction: Vertically stack the CrPS4 layer on the dimethylsiloxane and another two-dimensional material layer under a microscope to form a heterojunction, where the CrPS4 layer serves as the resistive switching functional layer; Electrode preparation: Define the electrode pattern in the overlapping area of the heterojunction through a photolithography process, and evaporate the active metal to form the top electrode. The top electrode is in contact with the CrPS4 layer and another two-dimensional material layer respectively to form a vertical-structure heterojunction memristor.

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