Two-dimensional memristor material screening method and system and two-dimensional memristor material

Abstract

The invention provides a two-dimensional memristive material screening method and system and a two-dimensional memristive material, and relates to the technical field of two-dimensional memristive materials, and the method comprises the steps: obtaining a two-dimensional polar semiconductor material according to the physical and chemical properties of a two-dimensional material; manufacturing defects in the two-dimensional polar semiconductor material to obtain a defect material; first formation energy of the defect is calculated, and first ionization energy of the defect is calculated when the first formation energy is smaller than a formation energy threshold value; when the first ionization energy is smaller than an ionization energy threshold value, polarization overturning operation is carried out on the defect material so as to change the conductive property of the defect material; calculating second ionization energy of the defect after polarization flipping so as to calculate a difference value between the first ionization energy and the second ionization energy; and taking the two-dimensional polar semiconductor material of which the difference value is greater than a difference value threshold value as a two-dimensional memristor material. The two-dimensional memristor material with the resistance change property can be screened out only by calculating the formation energy and ionization energy of different defects, the material screening efficiency can be improved, and the problem that the two-dimensional memristor material is difficult to screen is solved.

Description

Technical Field

[0001] The present application relates to the technical field of two-dimensional memristor materials, and in particular to a two-dimensional memristor material screening method, system and two-dimensional memristor material. Background Art

[0002] A memristor is a non-volatile memory device that can maintain its resistance state after the power is turned off and simultaneously realize computing and storage functions. A two-dimensional memristor is a memristor built on two-dimensional materials. The working principle of a two-dimensional memristor mainly relies on the formation and breaking of conductive filaments, and its core mechanism is the interaction between defects and electrodes. Under an appropriate electric field, the adsorbed atoms on the electrode can be migrated to the vacancies or grain boundaries of the two-dimensional material to form conductive filaments, thereby causing a reversible change in resistance.

[0003] However, these two-dimensional materials do not have the ability to switch resistance by themselves, and resistance switching is also extremely dependent on material defects and the role of metal electrodes. This defect-dependent mechanism can easily damage the material, limiting the durability and performance consistency of the two-dimensional memristor. The cycle life of the two-dimensional memristor formed by the above mechanism is less than 10 2 It is about 10 times, which cannot meet the requirements of long-term stable operation of memristors. Therefore, it is necessary to find a two-dimensional memristor material that can achieve resistance change by changing its own structure.

[0004] When searching for materials suitable for two-dimensional memristors, the trial and error method is often used, that is, the two-dimensional material is selected based on personal experience, and the synthesis and testing are used to verify whether it has memristive characteristics. However, the trial and error process of this method is costly and has a low success rate. It is difficult to obtain two-dimensional memristive materials with suitable memristive characteristics. Moreover, this method is inefficient and lacks systematicity. Summary of the invention

[0005] The present application provides a two-dimensional memristor material screening method, system and two-dimensional memristor material to solve the problem of difficulty in screening two-dimensional memristor materials.

[0006] The first aspect of the present application provides a two-dimensional memristor material screening method, comprising:

[0007] Obtaining a two-dimensional polar semiconductor material according to the physical and chemical properties of the two-dimensional material, wherein the two-dimensional polar semiconductor material is a material having polarization characteristics;

[0008] Creating defects in the two-dimensional polar semiconductor material to obtain a defective material;

[0009] calculating a first formation energy of the defect, and when the first formation energy is less than a formation energy threshold, calculating a first ionization energy of the defect;

[0010] When the first ionization energy is less than an ionization energy threshold, performing a polarization reversal operation on the defective material to change the conductive properties of the defective material;

[0011] Calculating a second ionization energy of the defect after polarization reversal to calculate a difference between the first ionization energy and the second ionization energy;

[0012] The two-dimensional polar semiconductor material whose difference is greater than a difference threshold is used as the two-dimensional memristive material.

[0013] Optionally, the physicochemical properties include space group number and band gap information, and obtaining the two-dimensional polar semiconductor material according to the physicochemical properties of the two-dimensional material includes:

[0014] Determining the inversion symmetry of the two-dimensional material according to the space group number;

[0015] If the two-dimensional material does not have the inversion symmetry, the two-dimensional material is marked as a polar material;

[0016] Acquire material properties of the polar material according to the band gap information, wherein the material properties include metal material, semiconductor material and insulating material;

[0017] When the material property is the semiconductor material, the polar material is marked as the two-dimensional polar semiconductor material.

[0018] Optionally, the step of creating defects in the two-dimensional polar semiconductor material to obtain a defective material comprises:

[0019] Identifying inequivalent atoms in the two-dimensional polar semiconductor material to obtain inequivalent atomic sites;

[0020] Expanding the two-dimensional polar semiconductor material to obtain a supercell structure;

[0021] The inequivalent atomic sites in the supercell structure are traversed, and one of the inequivalent atoms is deleted each time to create defects, thereby obtaining the defective material. The defective material has a single vacancy defect, and different defective materials have different defect positions.

[0022] Optionally, the physical and chemical properties further include a crystal structure, and the identifying of inequivalent atoms in the two-dimensional polar semiconductor material to obtain inequivalent atomic sites includes:

[0023] performing space group operations on the two-dimensional polar semiconductor material according to the crystal structure to identify inequivalent atoms;

[0024] The Wyckoff positions of the inequivalent atoms are obtained according to the space group operation to obtain the inequivalent atomic sites.

[0025] Optionally, after the step of traversing the inequivalent atomic sites in the supercell structure and deleting one inequivalent atom at a time to create defects and obtain the defective material, the step further includes:

[0026] Optimizing the defects in the defect material by first principles so that the unit cell energy of the defect material is the lowest after the defect optimization;

[0027] The vacuum layer thickness of the defect is changed to calculate the unit cell energy of the defect material according to the defect with different vacuum layer thicknesses.

[0028] Optionally, the optimizing the defects in the defective material by first principles includes:

[0029] Setting parameters for the first principle calculation, including pseudopotential, cutoff energy and k-point mesh;

[0030] The defects are optimized by an iterative convergence criterion.

[0031] Optionally, the first formation energy is the formation energy under the gel background charge model, and the first formation energy of the defect is calculated by the following formula:

[0032] ΔH f (q,w)=E tot (q,w)-E tot (host)+∑ i n i (E i +μ i )+q(ε VBM +ε F );

[0033] Where w is the defect, q is the charge state of the defect, ΔH f (q,w) is the first formation energy, E tot (q,w) is the total energy of the unit cell when the defect charge is q, E tot (host) is the unit cell energy without defects, i is the inequivalent atom, n i is the number of inequivalent atoms deleted, E i is the chemical potential of non-equivalent atoms at normal temperature and pressure, μ i is the environmental chemical potential, ε F is the Fermi level, ε VBM is the valence band top energy.

[0034] Optionally, when the first formation energy is less than a formation energy threshold, calculating the first ionization energy of the defect includes:

[0035] calculating the transition energy levels of the defect in different charged states, so as to calculate the initial ionization energy of the defect according to the transition energy levels;

[0036] The initial ionization energy is corrected to obtain the first ionization energy.

[0037] The second aspect of the present application provides a two-dimensional memristor material screening system, which applies the two-dimensional memristor material screening method provided in the first aspect, and the system comprises:

[0038] An acquisition module: used to acquire a two-dimensional polar semiconductor material according to the physical and chemical properties of the two-dimensional material, wherein the two-dimensional polar semiconductor material is a material having polarization characteristics;

[0039] A first building block is used to create defects in the two-dimensional polar semiconductor material to obtain a defect material;

[0040] A first calculation module: used to calculate a first formation energy of the defect, and when the first formation energy is less than a formation energy threshold, calculate a first ionization energy of the defect;

[0041] A second building block: configured to perform a polarization reversal operation on the defective material when the first ionization energy is less than an ionization energy threshold, so as to change the conductive properties of the defective material;

[0042] A second calculation module: used to calculate a second ionization energy of the defect after polarization reversal, so as to calculate a difference between the first ionization energy and the second ionization energy;

[0043] A result output module is used to use the two-dimensional polar semiconductor material whose difference is greater than a difference threshold as the two-dimensional memristor material.

[0044] The third aspect of the present application provides a two-dimensional memristor material, which is screened by applying the two-dimensional memristor material screening method provided in the first aspect. The two-dimensional memristor material includes: Al 2 S 3 , Al 2 Se 3 , Al 2 Te 3 , Ga 2 S 3 , Ga 2 Se 3 , Ga 2 Te 3 ,In 2 S 3 andIn 2 Te 3 .

[0045] The present application provides a two-dimensional memristor material screening method, system and two-dimensional memristor material, the method comprising: obtaining a two-dimensional polar semiconductor material according to the physicochemical properties of the two-dimensional material; creating defects in the two-dimensional polar semiconductor material to obtain a defect material; calculating the first formation energy of the defect, and when the first formation energy is less than the formation energy threshold, calculating the first ionization energy of the defect; when the first ionization energy is less than the ionization energy threshold, performing a polarization reversal operation on the defect material to change the conductive properties of the defect material; calculating the second ionization energy of the defect after the polarization reversal to calculate the difference between the first ionization energy and the second ionization energy; using the two-dimensional polar semiconductor material whose difference is greater than the difference threshold as a two-dimensional memristor material. The method only needs to calculate the formation energy and ionization energy of different defects, and can systematically and massively screen out two-dimensional memristor materials that have resistive properties. Compared with the experimental trial and error method, it can improve the efficiency of material screening and optimization, and solve the problem of difficulty in screening two-dimensional memristor materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0047] Figure 1 A schematic diagram of a two-dimensional memristor material screening method provided in an embodiment of the present application;

[0048] Figure 2 A schematic diagram of the entire process of the two-dimensional memristor material screening method provided in an embodiment of the present application;

[0049] Figure 3 A schematic diagram of the structure of a two-dimensional memristive material screening system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0050] The following embodiments are described in detail, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following embodiments do not represent all implementations consistent with the present application. They are only examples of systems and methods consistent with some aspects of the present application as detailed in the claims.

[0051] When constructing a two-dimensional memristor using two-dimensional materials, it is necessary to find suitable two-dimensional materials. In some embodiments, a trial-and-error method is used, that is, the two-dimensional material is selected based on personal experience, and it is verified through synthesis and testing whether it has memristive characteristics. However, the trial-and-error process of this method is costly and has a low success rate. It is difficult to obtain a two-dimensional memristive material with suitable memristive characteristics. In addition, this method is inefficient and lacks systematicity.

[0052] In order to solve the problem of difficulty in screening two-dimensional memristor materials, some embodiments of the present application first provide a two-dimensional memristor material screening method, see Figure 1 , methods include:

[0053] S100: Obtaining a two-dimensional polar semiconductor material according to the physical and chemical properties of the two-dimensional material.

[0054] Two-dimensional polar semiconductor materials are materials with polarization properties. Polarization properties refer to the asymmetric structure of the upper and lower surfaces of the two-dimensional material, which leads to asymmetric charge distribution, so that the material has an electric dipole moment. Such materials with polarization properties are polar materials. In some embodiments, the physicochemical properties of the two-dimensional material can be obtained through a two-dimensional material database such as 2DmatPedia. The obtained physicochemical properties may include space group number and band gap information. Obtaining a two-dimensional polar semiconductor material according to the physicochemical properties of the two-dimensional material includes the following steps:

[0055] S110: Determine the inversion symmetry of two-dimensional materials based on the space group number.

[0056] Inversion symmetry is one of the key factors in determining whether a two-dimensional material is a polar material. Therefore, before obtaining a two-dimensional polar semiconductor material, the inversion symmetry of the two-dimensional material should be determined first. The space group number is a classification method used to describe the symmetry of the atomic arrangement in the crystal. Each space group has specific symmetry characteristics. By querying the space group number of the two-dimensional material, the symmetry of the two-dimensional material can be analyzed, and then it can be determined whether the two-dimensional material has inversion symmetry.

[0057] S120: If the two-dimensional material does not have inversion symmetry, the two-dimensional material is marked as a polar material.

[0058] When a two-dimensional material does not have inversion symmetry, the two-dimensional material may have polarization properties. Therefore, the two-dimensional material that does not have inversion symmetry is marked as a polar material.

[0059] S130: Obtaining material properties of the polar material according to the band gap information.

[0060] Material properties include metal materials, semiconductor materials and insulating materials. The band gap information provided by the two-dimensional material database can be used to determine whether the two-dimensional material is a semiconductor. For example, the material properties of polar materials can be determined by the size of the band gap. When the band gap of the polar material is within the two-dimensional semiconductor range (approximately 0eV to 8eV), the material property of the polar material can be determined to be a semiconductor material.

[0061] S140: When the material property is a semiconductor material, marking the polar material as a two-dimensional polar semiconductor material.

[0062] S200: creating defects in a two-dimensional polar semiconductor material to obtain a defective material.

[0063] The steps include:

[0064] S210: Identify inequivalent atoms in the two-dimensional polar semiconductor material to obtain inequivalent atomic sites.

[0065] In some embodiments, the physical and chemical properties further include a crystal structure, and identifying inequivalent atoms in the two-dimensional polar semiconductor material to obtain inequivalent atomic sites includes the following steps:

[0066] S211: Perform space group manipulations on two-dimensional polar semiconductor materials based on their crystal structures to identify inequivalent atoms.

[0067] It can be understood that equivalent atoms are atoms with the same local environment, and inequivalent atoms are atoms in asymmetric positions in the crystal structure. Space group operations include operations such as translation, rotation, mirroring and inversion. Through these space group operations, it can be determined which atoms have the same local environment, that is, equivalent atoms can be identified. Inequivalent atoms cannot be transformed into each other through the above-mentioned space group operations such as translation, rotation, mirroring and inversion, that is, inequivalent atoms can be identified.

[0068] S212: Obtain the Wyckoff positions of inequivalent atoms according to space group operations to obtain inequivalent atomic sites.

[0069] The Wyckoff position is used to describe the equivalent position that an atom may occupy in a given space group. After performing space group operations on a two-dimensional polar semiconductor material, each Wyckoff position corresponds to a set of equivalent points generated by the space group operation, that is, the atomic sites can be determined when the Wyckoff position is known, and these atomic sites include equivalent atomic sites and inequivalent atomic sites. The process of obtaining inequivalent atomic sites based on the Wyckoff position can be obtained through the prior art and is not described in detail in this application.

[0070] S220: Expand the two-dimensional polar semiconductor material to obtain a supercell structure.

[0071] In some embodiments, the cell expansion direction can be selected according to the dimensional characteristics of the material. For two-dimensional materials, the a and b directions are preferentially expanded, while a larger vacuum layer is retained in the c direction to avoid interlayer interactions. The a, b, and c directions refer to the three main axis directions in the crystal structure. For two-dimensional materials, the a and b directions are usually located in the plane of the material, while the c direction is perpendicular to the plane. Secondly, the cell expansion multiple (for example, 3×3, 4×4, etc.) is dynamically adjusted according to the number of atoms or lattice constant of the original cell so that the number of atoms of the two-dimensional polar semiconductor material after cell expansion is within a reasonable range (for example, 100 to 200 atoms). After cell expansion, a supercell structure is obtained. By expanding the cell, the defect concentration can be made as low as possible during subsequent defect manufacturing.

[0072] S230: traverse the inequivalent atomic sites in the supercell structure, and delete one inequivalent atom each time to create defects and obtain defective materials.

[0073] When manufacturing defects, the embodiments of the present application only construct defective materials through point defects, which are the most common in materials and easy to implement in calculations. It can be understood that since only one non-equivalent atom is deleted each time, the resulting defective material has a single vacancy defect, and the defect positions of different defective materials are different.

[0074] Since the charge distribution near the defect will change significantly with the change of valence state, and even the atomic structure may have a great impact, the structure needs to be re-optimized for each defect valence state. Therefore, in some embodiments, the inequivalent atomic sites in the supercell structure are traversed, and one inequivalent atom is deleted each time to create defects. After the step of obtaining the defective material, the following steps are also included:

[0075] S240: Optimizing defects in the defective material by first principles, so that the unit cell energy of the defective material is the lowest after the defect optimization.

[0076] The optimization of defects in defective materials by first principles specifically includes the following steps:

[0077] S241: Set the parameters for first-principles calculations, including pseudopotential, plane wave cutoff energy, and k-point mesh.

[0078] In the process of first-principles calculation of defect structure optimization, choosing a suitable pseudopotential is a key step. The pseudopotential should match the element type of the two-dimensional polar semiconductor material and include the number and distribution of valence electrons. The setting of the plane wave cutoff energy will affect the calculation accuracy and efficiency. The plane wave cutoff energy should be further improved on the basis of the primitive cell so that the total energy and force of the defect material can reach the required convergence accuracy. By gradually increasing the plane wave cutoff energy and observing the change in material energy, a balance point can be found to optimize between accuracy and computing resources. The choice of k-point grid is particularly important for the calculation of electronic structure. For two-dimensional materials, a dense k-point grid is used in the material plane, and only a single k-point is required in the vertical direction.

[0079] S242: Optimizing defects through iterative convergence criteria.

[0080] The optimization of defective structures should follow the iterative convergence criterion. The convergence criterion of force can be set at After the defect optimization is completed, the unit cell energy is minimized. By optimizing the defects, the accuracy can be improved while improving the efficiency and repeatability of the calculation, providing a reliable basis for subsequent calculation analysis.

[0081] S250: changing the vacuum layer thickness of the defect to calculate the unit cell energy of the defect material according to the defects with different vacuum layer thicknesses.

[0082] Different vacuum layer thicknesses will affect the charge distribution and electrostatic potential of the defect material. In the process of calculating the ionization energy of the defect, the unit cell energy of the defect material at different vacuum layer thicknesses is needed for fitting, so the vacuum layer thickness of the defect needs to be changed. In some embodiments, the vacuum layer thickness can be increased directly on the optimized defect without re-optimizing the entire crystal structure to save calculation time and maintain the integrity of the optimized structure. For two-dimensional materials, the vacuum layer thickness can be gradually increased, for example, from Start by increasing each time To ensure complete shielding of the interlayer interaction. At the same time, the vacuum layer thickness should not be too large, otherwise it will lead to the "ghost state" phenomenon, that is, the charge is no longer evenly distributed on both sides of the material, but at both ends of the z-axis of the supercell structure, that is, an abnormal charge distribution is formed on the contact surface of the vacuum layer. This phenomenon will affect the accuracy of the calculation results and lead to calculation errors of ionization energy or other electronic properties. For example, in the calculation of the ionization energy of two-dimensional hexagonal boron nitride, the vacuum thickness is greater than Afterwards, ghostly phenomena will appear.

[0083] S300: Calculate a first formation energy of a defect, and when the first formation energy is less than a formation energy threshold, calculate a first ionization energy of the defect.

[0084] When subsequently calculating the first ionization energy of the defect, it is necessary to calculate the energy of the defect in different valence states. In the first principle calculation, this can be achieved by adjusting the total number of electrons in the defect material. At the same time, the compensation background charge is automatically introduced to maintain the electrical neutrality of the defect material. This is the gel background charge model approximation. The first formation energy is the formation energy under the gel background charge model approximation. In some embodiments, the first formation energy of the defect can be calculated by the following formula:

[0085] ΔH f (q,w)=E tot (q,w)-E tot (host)+∑ i n i (E i +μ i )+q(ε VBM +ε F );

[0086] Where w is the defect, q is the charge state of the defect, ΔH f (q,w) is the first formation energy, E tot (q,w) is the total energy of the unit cell when the defect charge is q, E tot (host) is the unit cell energy without defects, i is the inequivalent atom, n i is the number of inequivalent atoms deleted, E i is the chemical potential of non-equivalent atoms at normal temperature and pressure, μ i is the environmental chemical potential, ε F is the Fermi level, ε VBM is the valence band top energy. According to step S230, in the implementation of this application, n i =1.

[0087] In order to screen out two-dimensional materials with defect-polarization coupling characteristics, at least one defect should have a small formation energy, that is, when the first formation energy is less than the formation energy threshold, it means that the defect is easier to form in the material, and the two-dimensional polar semiconductor material can be preliminarily determined to be an effective two-dimensional memristor. If the first formation energy is greater than the formation energy threshold, the two-dimensional polar semiconductor material is an invalid material. When the first formation energy of the defect is less than the formation energy threshold, the first ionization energy of the defect is calculated.

[0088] When the first formation energy is less than the formation energy threshold, calculating the first ionization energy of the defect comprises the following steps:

[0089] S310: Calculating transition energy levels of defects in different charged states, so as to calculate initial ionization energy of the defects according to the transition energy levels.

[0090] Ionization energy is the energy required to ionize the electrons or holes of impurities from the defect energy level to the corresponding band edge state to become free carriers. The transition energy level represents the Fermi energy level of the defect material when the defect is ionized. Therefore, the ionization energy of the defect can be calculated from the transition energy level. When the same defect has the same formation energy in different charged states, the Fermi energy level at this time is called the transition energy level. The transition energy level can be calculated by the following formula:

[0091] ε(q / q′)+ε VBM =[E tot (q,w)-E tot (q ′ ,w)] / (q ′ -q);

[0092] Among them, ε(q / q′) is the transition energy level, E tot (q ′ ,w) is the defect charge q ′ The total energy of the unit cell is , and q and q′ are the different charged states of the defect.

[0093] The initial ionization energy of the defect can be the donor ionization energy or the acceptor ionization energy. When q is (+1 / 0), the transition energy level of the donor is ε(+1 / 0). From the defect state ionization electron to the bottom of the conduction band, the donor ionization energy of the defect can be calculated by the following formula:

[0094] IE a =ε CBM -ε(+1 / 0);

[0095] Among them, IE 1 is the donor ionization energy, ε CBM is the conduction band bottom energy, and ε(+1 / 0) is the transition energy level of the donor.

[0096] q ′ When the value is (0 / -1), the transition energy level of the acceptor ionizing a hole is ε(0 / -1), from the defect state ionizing the hole to the valence band top, so the acceptor ionization energy of the defect can be calculated by the following formula:

[0097] IE b =ε(0 / -1)-ε VBM ;

[0098] Among them, IE b is the acceptor ionization energy, and ε(0 / -1) is the acceptor transition energy level. a and IE b is the initial ionization energy of the defect.

[0099] S320: Correcting the initial ionization energy to obtain a first ionization energy.

[0100] Since the background charge distribution area of ​​3D materials coincides with the distribution area of ​​free charges after real ionization, the above method can be used to accurately calculate the ionization energy of defects in 3D materials. However, for 2D materials, the background charge distribution of the gel background charge model extends to the entire vacuum layer, which is different from the localization of free electrons near the 2D plane after actual ionization. This leads to a large Coulomb interaction between the background charge and the charged defects. At the same time, the thickness of the vacuum layer will also affect the background charge density, thereby changing the Coulomb interaction, causing the defect ionization energy and formation energy in the 2D material to diverge as the size of the vacuum layer increases. Therefore, unlike 3D materials, the accurate ionization energy of 2D materials cannot be calculated with arbitrary size, nor can the interaction between defects be ignored by simply expanding the lateral size.

[0101] In order to improve the accuracy of the calculation results, the WLZ method is used in the embodiment of the present application to correct the initial ionization energy of the defect. The WLZ method corrects the problem of divergence of the ionization energy of the two-dimensional material so that the ionization energy can converge. The initial ionization energy of the defect can be corrected by the following formula:

[0102]

[0103] Among them, IE(S,L Z ) is the initial ionization energy of the defect, and its value is similar to IE a or IE b Equal;IE 1 is the true ionization energy of the defect, i.e., the first ionization energy; S is the transverse cross-sectional area of ​​the defect material; L Z is the vacuum layer thickness of the defect; α is the Madelung constant, which can be obtained by fitting the unit cell energy of the defect material at different vacuum layer thicknesses in step S250; β is the coefficient phase, β=e 2 / (24ε 0 ), e is the amount of charge changed during the ionization process, ε 0 is the dielectric constant of vacuum; is the electrostatic Coulomb energy between periodically charged defects; is the Coulomb energy between the uniformly charged plane and the gel background charge. Since the two-dimensional material is a very thin material, it can be considered that the dielectric constant of the defect material is close to the vacuum dielectric constant ε 0 In the process of correcting the initial ionization energy, different L Z The fitting result is Z Approach IE 1 .

[0104] S400: When the first ionization energy is less than the ionization energy threshold, a polarization reversal operation is performed on the defective material to change the conductive property of the defective material.

[0105] When the first ionization energy is less than the ionization energy threshold, it means that the defect is easy to ionize, and the two-dimensional polar semiconductor material is again determined to be an effective two-dimensional memristive material. If the first ionization energy is greater than the ionization energy threshold, the two-dimensional polar semiconductor material is an invalid material. When the first ionization energy of the defect is less than the ionization energy threshold, the defect material is subjected to a polarization reversal operation. It can be understood that the polarization reversal of the ferroelectric material can be achieved by applying a reverse electric field, thereby regulating the conductive properties of the material. In the process of polarization reversal, the position of the defect in the defect material with a supercell structure remains almost unchanged before and after the polarization reversal, so the polarization direction can be reversed by adjusting the position of atoms outside the defect without making significant changes to the defect position. This operation can reflect the change in the type of defects caused by the polarization reversal of the material, thereby changing the conductive properties of the material.

[0106] S500: calculating a second ionization energy of the defect after polarization reversal to calculate a difference between the first ionization energy and the second ionization energy.

[0107] The calculation method of the second ionization energy is the same as the calculation method of the first ionization energy, and will not be described in this step. After the second ionization energy is calculated, the difference between the two ionization energies can be calculated based on the first ionization energy and the second ionization energy.

[0108] S600: Using the two-dimensional polar semiconductor material whose difference is greater than the difference threshold as a two-dimensional memristor material.

[0109] In addition to the formation energy of the defect, it is also necessary to compare the ionization energy of the defect in the two polarization states of upper polarization and lower polarization, that is, before and after the polarization reversal, because the change in ionization energy directly affects the conductivity of the material. Only when there is a large difference in the ionization energy of the defect in the two polarization states will it lead to a significant change in the conductivity of the material. Especially in memristors, the difference in ionization energy will cause the material to switch between high and low resistance states, thereby reversing the polarization under the action of an external electric field or voltage, producing an adjustable conductivity state, and realizing the memristive properties of the material. Therefore, when screening two-dimensional memristive materials, two-dimensional polar semiconductor materials with a difference greater than the difference threshold are used as two-dimensional memristive materials. This type of material can show changes in conductive properties under the drive of an electric field, and the conductivity state can be adjusted by controlling the external electric field to realize the functions of information storage and processing.

[0110] It should also be noted that, for the defective material formed by deleting the inequivalent atoms in the above step S230, as long as one of the defects satisfies the calculation result in step S600, the two-dimensional polar semiconductor material is a two-dimensional memristive material. In the embodiment of the present application, the formation energy threshold, the ionization energy threshold and the difference threshold can be set according to the specific selected materials, and no examples are given in the embodiment of the present application.

[0111] See also Figure 2The screening process of the two-dimensional memristor material provided in this application can be Figure 2 To express. The screening method provided in the embodiment of the present application uses a first-principles calculation method and is based on the defect polarization coupling principle to determine whether a two-dimensional material can achieve resistance change through its own structural transformation. It only needs to calculate the formation energy and ionization energy of different defects to systematically and massively screen out two-dimensional memristive materials that have resistive properties. Compared with the experimental trial and error method, the theoretical simulation method is easier to screen two-dimensional memristive materials, which can improve the efficiency of material screening and optimization and solve the problem of difficulty in screening two-dimensional memristive materials.

[0112] Through the screening method provided in the above embodiment, the following two-dimensional memristor materials can be screened out, including: Al 2 S 3 , Al 2 Se 3 , Al 2 Te 3 , Ga 2 S 3 , Ga 2 Se 3 , Ga 2 Te 3 ,In 2 S 3 andIn 2 Te 3 .

[0113] Based on the above method, some embodiments of the present application also provide a two-dimensional memristor material screening system, which is applied to the two-dimensional memristor material screening method provided in the above embodiment, see Figure 3 , the system includes:

[0114] Acquisition module: used to obtain two-dimensional polar semiconductor materials based on the physical and chemical properties of two-dimensional materials.

[0115] Among them, the two-dimensional polar semiconductor material is a material with polarization properties.

[0116] The first building block is used to create defects in two-dimensional polar semiconductor materials to obtain defective materials.

[0117] The first calculation module is used to calculate the first formation energy of the defect, and when the first formation energy is less than the formation energy threshold, calculate the first ionization energy of the defect.

[0118] The second building block is used to perform a polarization reversal operation on the defective material when the first ionization energy is less than the ionization energy threshold, so as to change the conductive properties of the defective material.

[0119] The second calculation module is used to calculate the second ionization energy of the defect after the polarization reversal, so as to calculate the difference between the first ionization energy and the second ionization energy.

[0120] Result output module: used for treating the two-dimensional polar semiconductor material whose difference is greater than the difference threshold as a two-dimensional memristor material.

[0121] It can be seen from the above technical solutions that the embodiments of the present application provide a two-dimensional memristor material screening method, system and two-dimensional memristor material, the method comprising: obtaining a two-dimensional polar semiconductor material according to the physicochemical properties of the two-dimensional material; creating defects in the two-dimensional polar semiconductor material to obtain a defective material; calculating the first formation energy of the defect, and when the first formation energy is less than the formation energy threshold, calculating the first ionization energy of the defect; when the first ionization energy is less than the ionization energy threshold, performing a polarization reversal operation on the defective material to change the conductive properties of the defective material; calculating the second ionization energy of the defect after the polarization reversal to calculate the difference between the first ionization energy and the second ionization energy; using the two-dimensional polar semiconductor material whose difference is greater than the difference threshold as a two-dimensional memristor material. The method only needs to calculate the formation energy and ionization energy of different defects, and can systematically and massively screen out two-dimensional memristor materials that have resistive properties. Compared with the experimental trial and error method, it can improve the efficiency of material screening and optimization, and solve the problem of difficulty in screening two-dimensional memristor materials.

[0122] Similar parts between the embodiments provided in this application can be referenced to each other. The specific implementation methods provided above are only a few examples under the general concept of this application and do not constitute a limitation on the protection scope of this application. For those skilled in the art, any other implementation methods expanded based on the scheme of this application without creative work belong to the protection scope of this application.

Claims

1. A two-dimensional memristor material screening method, characterized in that: include: Obtaining a two-dimensional polar semiconductor material according to the physical and chemical properties of the two-dimensional material, wherein the two-dimensional polar semiconductor material is a material having polarization characteristics; Creating defects in the two-dimensional polar semiconductor material to obtain a defective material; calculating a first formation energy of the defect, and when the first formation energy is less than a formation energy threshold, calculating a first ionization energy of the defect; When the first ionization energy is less than an ionization energy threshold, performing a polarization reversal operation on the defective material to change the conductive properties of the defective material; Calculating a second ionization energy of the defect after polarization reversal to calculate a difference between the first ionization energy and the second ionization energy; The two-dimensional polar semiconductor material whose difference is greater than a difference threshold is used as the two-dimensional memristive material.

2. The two-dimensional memristor material screening method according to claim 1, characterized in that: The physicochemical properties include space group number and band gap information, and obtaining the two-dimensional polar semiconductor material according to the physicochemical properties of the two-dimensional material includes: Determining the inversion symmetry of the two-dimensional material according to the space group number; If the two-dimensional material does not have the inversion symmetry, the two-dimensional material is marked as a polar material; Acquire material properties of the polar material according to the band gap information, wherein the material properties include metal material, semiconductor material and insulating material; When the material property is the semiconductor material, the polar material is marked as the two-dimensional polar semiconductor material.

3. The two-dimensional memristor material screening method according to claim 1, characterized in that: The step of creating defects in the two-dimensional polar semiconductor material to obtain a defective material comprises: Identifying inequivalent atoms in the two-dimensional polar semiconductor material to obtain inequivalent atomic sites; Expanding the two-dimensional polar semiconductor material to obtain a supercell structure; The inequivalent atomic sites in the supercell structure are traversed, and one of the inequivalent atoms is deleted each time to create defects, thereby obtaining the defective material. The defective material has a single vacancy defect, and different defective materials have different defect positions.

4. The two-dimensional memristor material screening method according to claim 3, characterized in that: The physical and chemical properties also include crystal structure, and the identifying of inequivalent atoms in the two-dimensional polar semiconductor material to obtain inequivalent atomic sites includes: performing space group operations on the two-dimensional polar semiconductor material according to the crystal structure to identify inequivalent atoms; The Wyckoff positions of the inequivalent atoms are obtained according to the space group operation to obtain the inequivalent atomic sites.

5. The two-dimensional memristor material screening method according to claim 3, characterized in that: After the step of traversing the inequivalent atomic sites in the supercell structure and deleting one inequivalent atom at a time to create defects and obtain the defective material, the step further includes: Optimizing the defects in the defect material by first principles so that the unit cell energy of the defect material is the lowest after the defect optimization; The vacuum layer thickness of the defect is changed to calculate the unit cell energy of the defect material according to the defect with different vacuum layer thicknesses.

6. The two-dimensional memristor material screening method according to claim 5, characterized in that: The optimizing the defects in the defective material by first principles includes: Setting parameters for the first principle calculation, including pseudopotential, cutoff energy and k-point mesh; The defects are optimized by an iterative convergence criterion.

7. The two-dimensional memristor material screening method according to claim 3, characterized in that: The first formation energy is the formation energy under the gel background charge model, and the first formation energy of the defect is calculated by the following formula: ΔH f (q,w)=E tot (q,w)-E tot (host)+∑ i n i (E i +μ i )+q(ε VBM +ε F ); Where w is the defect, q is the charge state of the defect, ΔH f (q,w) is the first formation energy, E tot (q,w) is the total energy of the unit cell when the defect charge is q, E tot (host) is the unit cell energy without defects, i is the inequivalent atom, n i is the number of inequivalent atoms deleted, E i is the chemical potential of non-equivalent atoms at normal temperature and pressure, μ i is the environmental chemical potential, ε F is the Fermi level, ε VBM is the valence band top energy.

8. The two-dimensional memristor material screening method according to claim 1, characterized in that: When the first formation energy is less than a formation energy threshold, calculating the first ionization energy of the defect comprises: calculating the transition energy levels of the defect in different charged states, so as to calculate the initial ionization energy of the defect according to the transition energy levels; The initial ionization energy is corrected to obtain the first ionization energy.

9. A two-dimensional memristive material screening system, characterized in that: The two-dimensional memristive material screening method applied to any one of claims 1 to 8, wherein the system comprises: An acquisition module: used to acquire a two-dimensional polar semiconductor material according to the physical and chemical properties of the two-dimensional material, wherein the two-dimensional polar semiconductor material is a material having polarization characteristics; A first building block is used to create defects in the two-dimensional polar semiconductor material to obtain a defect material; A first calculation module: used to calculate a first formation energy of the defect, and when the first formation energy is less than a formation energy threshold, calculate a first ionization energy of the defect; A second building block: configured to perform a polarization reversal operation on the defective material when the first ionization energy is less than an ionization energy threshold, so as to change the conductive properties of the defective material; A second calculation module: used to calculate a second ionization energy of the defect after polarization reversal, so as to calculate a difference between the first ionization energy and the second ionization energy; A result output module is used to use the two-dimensional polar semiconductor material whose difference is greater than a difference threshold as the two-dimensional memristor material.

10. A two-dimensional memristive material, characterized in that: The two-dimensional memristive material screening method described in any one of claims 1 to 8 is used for screening, and the two-dimensional memristive material includes: Al2S3, Al2Se3, Al2Te3, Ga2S3, Ga2Se3, Ga2Te3, In2S3 and In2Te3.

Images