Unipolar diamond memristor with electrical enhancement characteristic and preparation method thereof

Abstract

The invention discloses a unipolar diamond memristor with an electrical enhancement characteristic and a preparation method thereof, and aims to solve the technical problem that an existing memristor based on a transition metal chalcogenide, an oxide heterostructure or a small amount of carbon materials is difficult to be suitable for high-temperature, high-frequency and high-power working conditions. The unipolar diamond memristor comprises a diamond substrate, a resistive layer, a first contact electrode and a second contact electrode, the first contact electrode is arranged on one side of the surface of the diamond substrate, the first contact electrode and the diamond substrate form ohmic contact, the resistive layer is arranged on the other side of the surface of the diamond substrate, and the second contact electrode and the resistive layer form ohmic contact. The resistive layer is an amorphous carbon layer subjected to oxygen enrichment treatment, and a second contact electrode is deposited on the surface of the resistive layer. The rewritable nonvolatile memory is prepared by using diamond and has a stable storage window in a multi-stage resistance state, and a threshold voltage is related to a device area and a bias voltage amplitude, so that the characteristic of interface type unipolarity is shown.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor electronic devices, and in particular relates to a unipolar diamond memristor with electrically enhanced characteristics and a preparation method thereof. Background Art

[0002] With breakthroughs in artificial intelligence (AI) big models, the emergence of embodied AI, and the advent of the Internet of Things (IoT), sensor technology is evolving from single-mode data collection to neuromorphic devices that enable multimodal fusion and high-dimensional perception. Neuromorphic devices deeply integrate perception, storage, and computing by simulating the dynamic characteristics of biological neurons and synapses, achieving integrated sensing, storage, and computing. This architectural innovation transcends the storage bottleneck of the traditional von Neumann architecture, enabling the system to process information in a manner more similar to that of a biological nervous system, significantly improving energy efficiency and parallel processing capabilities. Memristors, a typical example of neuromorphic devices, possess multiple switchable resistance states and are crucial for realizing the next generation of neuromorphic computing and storage-computing integrated chips. The switching behavior of memristors has only been observed in transition metal chalcogenides (Huh W,Lee D, Lee C H. Memristors based on 2D materials as an artificial synapse forneuromorphic electronics[J]. Advanced materials, 2020, 32(51): 2002092.), oxide heterostructures (Strukov DB, Snider GS, Stewart DR, et al. The missing memristor found[J]. nature, 2008, 453(7191): 80-83.) and a small amount of carbon materials (Jeong HY, Kim JY,Kim JW, et al. Graphene oxide thin films for flexible nonvolatile memory applications[J]. Nano letters, 2010, 10(11): 4381-4386.). However, there is almost no research on wide bandgap semiconductors, especially the ultimate semiconductor diamond, which are widely used in extreme environments such as high temperature, high frequency and high power. Summary of the Invention

[0003] The purpose of the present invention is to solve the technical problems that existing memristors based on transition metal chalcogenides, oxide heterostructures or a small amount of carbon materials are difficult to apply to high-temperature, high-frequency and high-power working conditions, and do not have electrically enhanced characteristics, and to provide a unipolar diamond memristor with electrically enhanced characteristics and a preparation method thereof.

[0004] The unipolar diamond memristor with electrically enhanced characteristics of the present invention includes a diamond substrate, a resistive switching layer, a first contact electrode, and a second contact electrode. The first contact electrode is arranged on one side of the surface of the diamond substrate, and the first contact electrode forms an ohmic contact with the diamond substrate. The resistive switching layer is arranged on the other side of the surface of the diamond substrate. The resistive switching layer is an amorphous carbon (aC) layer treated with oxygen enrichment, and the second contact electrode is deposited on the surface of the resistive switching layer.

[0005] The preparation method of the unipolar diamond memristor with electrically enhanced characteristics of the present invention is achieved by the following steps:

[0006] 1. Ultrasonic cleaning is performed on the diamond substrate to obtain a cleaned diamond substrate;

[0007] 2. Performing surface termination treatment on the cleaned diamond substrate using a wet chemical method or a plasma method to obtain a terminal-treated diamond;

[0008] 3. Preparing an amorphous carbon (aC) layer on one side of the surface of the terminal-treated diamond by in-situ high-temperature catalysis of the transition metal metallized diamond to obtain a diamond with an amorphous carbon (aC) layer;

[0009] 4. Depositing a first contact electrode on the other side of the diamond surface with the amorphous carbon layer, and metallizing the diamond surface by high-temperature treatment at 750-850°C in an inert atmosphere or vacuum environment, so that the first contact electrode forms a low-resistance ohmic contact with the diamond substrate;

[0010] 5. Performing oxygen enrichment treatment on the diamond with the amorphous carbon (aC) layer to form a resistive switching layer, thereby obtaining a diamond with a resistive switching layer;

[0011] 6. depositing a second contact electrode on the resistive switching layer, thereby obtaining a unipolar diamond memristor with electrically enhanced characteristics;

[0012] The oxygen-enriched treatment in step five is oxygen plasma surface treatment, ultraviolet / ozone environment surface treatment or (high concentration) oxygen environment surface treatment.

[0013] The present invention provides a unipolar diamond memristor with electrically enhanced characteristics. A first metal contact layer is provided on the upper surface of a diamond substrate. The first metal contact layer has low-resistance ohmic contact characteristics. A resistive switching layer is provided on the other surface of the diamond substrate. The resistive switching layer is composed of an aC layer treated with oxygen enrichment. A second metal contact layer is deposited on the resistive switching layer. The resistive switching mechanism is that under the action of an electric field, the interface oxygen causes the aC layer to undergo an oxidation-reduction reaction, and the low-resistance sp 2 Carbon transforms into high-resistance sp 3 Carbon. Under cyclic bias sweeps, this invention uses diamond to fabricate a rewritable nonvolatile memory with a stable storage window of multi-level resistance states. The threshold voltage is correlated with the device area and bias amplitude, exhibiting interface-type unipolarity. The electrically enhanced unipolar diamond memristor described in this invention provides new ideas and methods for constructing efficient, high-performance integrated storage and computing hardware neural networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the structure of the unipolar diamond memristor with electrically enhanced characteristics of the present invention, wherein 1 is a diamond substrate, 2 is a resistive switching layer, 3 is a first contact electrode, and 4 is a second contact electrode;

[0015] Figure 2 The IV characteristic curve and device photo of the unipolar diamond memristor with electrically enhanced characteristics in the embodiment;

[0016] Figure 3 1 is a test diagram of the low-resistance state and high-resistance state distribution of the unipolar diamond memristor with electrically enhanced characteristics under multiple bias cycle scans in the embodiment;

[0017] Figure 4 This is a time response test diagram of the unipolar diamond memristor with electrically enhanced characteristics under current pulse stimulation in the embodiment. DETAILED DESCRIPTION

[0018] Specific embodiment 1: The unipolar diamond memristor with electrically enhanced characteristics in this embodiment includes a diamond substrate 1, a resistive layer 2, a first contact electrode 3 and a second contact electrode 4. The first contact electrode 3 is provided on one side of the surface of the diamond substrate 1, and the first contact electrode 3 forms an ohmic contact with the diamond substrate 1. The resistive layer 2 is provided on the other side of the surface of the diamond substrate 1. The resistive layer 2 is an amorphous carbon (aC) layer treated with oxygen enrichment, and the second contact electrode 4 is deposited on the surface of the resistive layer 2.

[0019] In this embodiment, the amorphous carbon (aC) layer can be formed by in-situ high-temperature catalysis of transition metal metallized diamond, or by in-situ transformation of diamond by laser heat treatment, or by deposition on diamond by common vacuum coating methods such as PVD and CVD.

[0020] This embodiment has a unipolar diamond memristor structure with electrically enhanced characteristics, including a diamond substrate, an oxygen-rich aC resistive switching layer, a low-resistance ohmic contact electrode, and an electrode in contact with the resistive switching layer. The surface terminal type is a chemical terminal such as a hydrogen terminal, an oxygen terminal, a nitrogen terminal, and a fluorine terminal that have been surface-treated; the ohmic contact has extremely low contact resistance and a low load voltage in the circuit loop, which can reduce interface losses during device operation; the oxygen-rich aC resistive switching layer can undergo an oxidation-reduction reaction caused by interface oxygen under the action of an electric field, which can be converted from a low-resistance sp 2 Carbon transforms into high-resistance sp 3 Carbon enables the device to exhibit a stable storage window with multiple resistance states. Compared to other resistance-changing materials, carbon offers advantages such as simple chemical composition, low cost, high stability, and compatibility with CMOS processes. It provides a new approach and method for building integrated storage and computing hardware neural networks.

[0021] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the diamond substrate 1 is single crystal diamond, polycrystalline diamond, intrinsic diamond or doped diamond.

[0022] Specific embodiment three: This embodiment is different from specific embodiment one or two in that the surface of the diamond substrate 1 has hydrogen terminations, oxygen terminations, nitrogen terminations or fluorine terminations.

[0023] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the material of the first contact electrode 3 is a transition metal from group IIIB (third subgroup) to group VIII (eighth group).

[0024] In this embodiment, when the diamond substrate has a hydrogen terminal, the first metal film layer is composed of one or more metal films such as Au / Pt with a work function higher than 5 eV.

[0025] Specific embodiment 5: This embodiment is different from any one of specific embodiments 1 to 4 in that the second contact electrode 4 is made of a laminated electrode formed of one or more metals selected from the group consisting of Al, Ag, Pt, and Ti.

[0026] Specific embodiment 6: This embodiment is different from any one of specific embodiments 1 to 5 in that the thickness of the first contact electrode 3 and the second contact electrode 4 is 10-1000 nm.

[0027] Specific embodiment seven: The preparation method of the unipolar diamond memristor with electrically enhanced characteristics in this embodiment is implemented according to the following steps:

[0028] 1. Ultrasonic cleaning is performed on the diamond substrate 1 to obtain a cleaned diamond substrate;

[0029] 2. Performing surface termination treatment on the cleaned diamond substrate using a wet chemical method or a plasma method to obtain a terminal-treated diamond;

[0030] 3. Preparing an amorphous carbon (aC) layer on one side of the surface of the terminal-treated diamond by in-situ high-temperature catalysis of the transition metal metallized diamond to obtain a diamond with an amorphous carbon (aC) layer;

[0031] 4. Depositing a first contact electrode 3 on the other side of the diamond surface with the amorphous carbon layer, and metallizing the diamond surface by high-temperature treatment at 750-850°C in an inert atmosphere or vacuum environment, so that the first contact electrode 3 forms a low-resistance ohmic contact with the diamond substrate 1;

[0032] 5. Performing oxygen enrichment treatment on the diamond with the amorphous carbon (aC) layer to form a resistive switching layer 2, thereby obtaining a diamond with a resistive switching layer;

[0033] 6. depositing a second contact electrode 4 on the resistive switching layer 2, thereby obtaining a unipolar diamond memristor with electrically enhanced characteristics;

[0034] The oxygen-enriched treatment in step five is oxygen plasma surface treatment, ultraviolet / ozone environment surface treatment or (high concentration) oxygen environment surface treatment.

[0035] Specific embodiment eight: This embodiment differs from specific embodiment seven in that in step one, the diamond substrate 1 is immersed in aqua regia for boiling treatment, and then ultrasonically cleaned using deionized water, alcohol, and acetone in sequence.

[0036] Specific embodiment nine: The difference between this embodiment and specific embodiment seven or eight is that the wet chemical method used in step two is to place the diamond substrate 1 in a mixed oxidizing strong acid and boil it at 350°C for 2 hours. The mixed oxidizing strong acid is a mixture of H2SO4 with a mass concentration of 98% and HNO3 with a mass concentration of 68% in a volume ratio of 3:1, so that the diamond substrate has oxygen terminals.

[0037] Specific embodiment 10: The difference between this embodiment and any one of specific embodiments 7 to 9 is that the plasma method used in step 2 is to perform surface termination treatment on the cleaned diamond substrate in a hydrogen, nitrogen, fluorine or oxygen plasma environment.

[0038] Specific embodiment 11: The difference between this embodiment and specific embodiments 7 to 10 is that the preparation process of the amorphous carbon (aC) layer in step 3 is as follows:

[0039] The Fe layer is deposited on one side of the surface of the terminal treated diamond by magnetron sputtering, and treated at 900℃ in an inert atmosphere or vacuum environment. The Fe layer catalyzes the diamond to produce sp2 The amorphous carbon layer is then washed away using hydrochloric acid.

[0040] The mass concentration of the hydrochloric acid described in this embodiment is 20%.

[0041] Example 1: The preparation method of the unipolar diamond memristor with electrically enhanced characteristics in this embodiment is implemented according to the following steps:

[0042] 1. Using aqua regia to wash away impurities on the surface of the diamond substrate 1, and then using deionized water, alcohol, and acetone to perform ultrasonic cleaning in sequence, and drying to obtain a cleaned diamond substrate;

[0043] Second, the surface of the cleaned diamond substrate was oxygen-terminated using a wet chemical method. The cleaned diamond substrate was placed in a mixed oxidizing strong acid and boiled at 350°C for 2 hours. The mixed oxidizing strong acid was a mixture of 98% H2SO4 and 68% HNO3 in a volume ratio of 3:1. This allowed the diamond substrate to be oxygen-terminated, resulting in a terminated diamond.

[0044] 3. Prepare an amorphous carbon (aC) layer on one side of the surface of the terminal treated diamond, and use magnetron sputtering technology to prepare (pattern) Fe layer on the diamond surface. Treat it at 900℃ under inert atmosphere, and Fe catalyzes the diamond to produce sp 2 aC in the state, and then Fe is washed away with hydrochloric acid to obtain diamond with an amorphous carbon (aC) layer;

[0045] 4. Depositing a first contact electrode 3 on the other side of the diamond surface with the amorphous carbon layer, and subjecting the diamond surface to a high-temperature treatment at 800° C. for 30 minutes in an inert atmosphere to metallize the diamond surface, so that the first contact electrode 3 forms a low-resistance ohmic contact with the diamond substrate 1;

[0046] 5. The diamond with the amorphous carbon (aC) layer is subjected to oxygen enrichment treatment to form a resistive switching layer 2. The oxygen enrichment treatment is carried out by introducing O2 at a flow rate of 5 sccm to form an oxygen plasma for oxygen enrichment treatment, thereby obtaining a diamond with a resistive switching layer;

[0047] 6. Depositing Pt with a thickness of 100 nm on the resistive layer 2 as the second contact electrode 4, thereby obtaining a unipolar diamond memristor with electrically enhanced characteristics;

[0048] The first contact electrode 3 is a Ti / Pt / Au laminated metal, and the thicknesses of the Ti / Pt / Au laminated layers are 30 nm / 30 nm / 70 nm respectively.

[0049] The unipolar diamond memristor with electrically enhanced characteristics described in this embodiment is formed by preparing an aC layer on the diamond surface and performing an oxygen-enriched treatment, and utilizing the redox reaction of the interface oxygen on the aC layer under the action of an electric field to generate a low-resistance sp 2 Carbon transforms into high-resistance sp 3 Carbon, thus showing the pinch hysteresis loop characteristics of the memristor under different amplitude bias sweeps, as shown in the attached Figure 2 As shown, Figure 2 In the figure, #1, #2 and #3 represent samples with different electrode areas. During the test, the ohmic contact electrode was grounded, while a bias voltage was applied to the resistive layer electrode. The device maintained a high resistance state at the initial state of 0 V. After applying a certain threshold voltage, the device entered a low resistance state with a large current. After the device returned to 0 V from the low resistance state, it underwent a reset operation and was reset to a high resistance state with a small current. The resistive threshold voltage is directly related to the device area, indicating that the resistive switching mechanism depends on the interface rather than the resistor wire, and the characteristic that it is related to the bias amplitude but not to the polarity indicates that the device is a unipolar memristor. After 10 bias cycle scans, the present invention used a read voltage of 29 V to read the resistance of the memristor in the low resistance and high resistance states, as shown in the attached figure. Figure 3 As shown in the figure, LRS represents the low resistance state and HRS represents the high resistance state. After multiple cycles, both resistance states of the device remain stable, indicating good repeatability. In addition, the low resistance state that depends on the limiting current shows that the device can achieve multi-level resistance state storage. When a 1000 Hz voltage pulse is applied to the diamond memristor of the present invention, the device current increases exponentially, showing the "non-associative learning-electrical enhancement sensitization reaction" in the neural synaptic response, such as Figure 4 shown.

Claims

1. A unipolar diamond memristor with electrically enhanced characteristics, characterized in that The unipolar diamond memristor with electrically enhanced characteristics comprises a diamond substrate (1), a resistive switching layer (2), a first contact electrode (3), and a second contact electrode (4); the first contact electrode (3) is provided on one side of the surface of the diamond substrate (1); the first contact electrode (3) forms an ohmic contact with the diamond substrate (1); the resistive switching layer (2) is provided on the other side of the surface of the diamond substrate (1); the resistive switching layer (2) is an amorphous carbon layer subjected to an oxygen-enriched treatment; and the second contact electrode (4) is deposited on the surface of the resistive switching layer (2).

2. The unipolar diamond memristor with electrically enhanced characteristics according to claim 1, characterized in that The diamond substrate (1) is single crystal diamond, polycrystalline diamond, intrinsic diamond or doped diamond.

3. The unipolar diamond memristor with electrically enhanced characteristics according to claim 1, characterized in that The surface of the diamond substrate (1) has hydrogen terminations, oxygen terminations, nitrogen terminations or fluorine terminations.

4. The unipolar diamond memristor with electrically enhanced characteristics according to claim 1, characterized in that The material of the first contact electrode (3) is a transition metal from group IIIB to group VIII.

5. The unipolar diamond memristor with electrically enhanced characteristics according to claim 1, characterized in that The material of the second contact electrode (4) is a laminated electrode formed by one or more metals selected from the group consisting of Al, Ag, Pt, and Ti.

6. The unipolar diamond memristor with electrically enhanced characteristics according to claim 1, characterized in that The thickness of the first contact electrode (3) and the second contact electrode (4) is 10-1000 nm.

7. The method for preparing a unipolar diamond memristor with electrically enhanced characteristics according to claim 1, characterized in that The preparation method of the unipolar diamond memristor with electrically enhanced characteristics is achieved by the following steps:

1. ultrasonically cleaning the diamond substrate (1) to obtain a cleaned diamond substrate; 2. Performing surface termination treatment on the cleaned diamond substrate using a wet chemical method or a plasma method to obtain a terminal-treated diamond; 3. Preparing an amorphous carbon layer on one side of the surface of the terminal-treated diamond by in-situ high-temperature catalysis of the transition metal metallized diamond to form the amorphous carbon layer, thereby obtaining a diamond with an amorphous carbon layer; 4. depositing a first contact electrode (3) on the other side of the surface of the diamond with the amorphous carbon layer, and metallizing the diamond surface by high temperature treatment at 750-850° C. in an inert atmosphere or vacuum environment, so that the first contact electrode (3) forms a low-resistance ohmic contact with the diamond substrate (1); 5. Performing oxygen enrichment treatment on the diamond with the amorphous carbon layer to form a resistive switching layer (2), thereby obtaining a diamond with a resistive switching layer; 6. depositing a second contact electrode (4) on the resistive layer (2), thereby obtaining a unipolar diamond memristor with electrically enhanced characteristics; The oxygen-enriched treatment in step five is oxygen plasma surface treatment, ultraviolet / ozone environment surface treatment or oxygen environment surface treatment.

8. The method for preparing a unipolar diamond memristor with electrically enhanced characteristics according to claim 7, characterized in that In step 2, the wet chemical method is to place the diamond substrate (1) in a mixed oxidizing strong acid and boil it at 350°C for 2 hours. The mixed oxidizing strong acid is a mixture of H2SO4 with a mass concentration of 98% and HNO3 with a mass concentration of 68% in a volume ratio of 3:1, so that the diamond substrate has oxygen terminals.

9. The method for preparing a unipolar diamond memristor with electrically enhanced characteristics according to claim 7, characterized in that The plasma method used in step 2 is to perform surface termination treatment on the cleaned diamond substrate in a hydrogen, nitrogen, fluorine or oxygen plasma environment.

10. The method for preparing a unipolar diamond memristor with electrically enhanced characteristics according to claim 7, characterized in that The preparation process of the amorphous carbon layer in step 3 is as follows: The Fe layer is deposited on one side of the surface of the terminal treated diamond by magnetron sputtering, and treated at 900℃ in an inert atmosphere or vacuum environment. The Fe layer catalyzes the diamond to produce sp 2 The amorphous carbon layer is then washed away using hydrochloric acid.

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