Nonvolatile memory device based on Cr2Cl3S3 / Ga2O3 heterostructure, construction method and application

Abstract

The invention discloses a nonvolatile memory device based on a Cr2Cl3S3 / Ga2O3 heterostructure, a construction method and application, and belongs to the field of nonvolatile memory devices. The construction method comprises the following steps: constructing a single layer of Cr2Cl3S3 and a single layer of Ga2O3; the preparation method comprises the following steps: stacking a single layer of Cr2Cl3S3 and a single layer of Ga2O3 so as to build two kinds of Cr2Cl3S3 / Ga2O3 heterostructures; according to the method, two kinds of Cr2Cl3S3 / Ga2O3 heterostructures are utilized to construct a nonvolatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructures; reversible switching of a ferromagnetic (FM) semiconductor Cr2Cl3S3 from a semiconductor state to a semimetal state can be realized by regulating and controlling the polarization direction of a ferroelectric (FE) material Ga2O3 through an electric field, and the process has a remarkable non-volatile characteristic: once the polarization direction is changed, the state (semiconductor or semimetal) of the Cr2Cl3S3 is kept unchanged until the next polarization direction is changed; this characteristic is particularly important for memory devices because it allows data to be preserved without a continuous electric field, thereby significantly reducing energy consumption and improving data stability.

Description

Technical Field

[0001] The present invention belongs to the field of non-volatile memory devices, and particularly relates to a non-volatile memory device based on a Cr2Cl3S3 / Ga2O3 heterostructure, a construction method, and an application thereof. Background Art

[0002] Due to the rise of two-dimensional materials such as graphene, two-dimensional materials have become a research hotspot in the fields of materials science and condensed matter physics due to their unique physical, chemical, and electronic properties. These materials not only have an atomic thickness, exhibiting excellent mechanical, electrical, and thermal properties, but also provide new possibilities for realizing high-performance electronic devices. In particular, their excellent properties demonstrated in electron transport, optical response, and spin manipulation make them have great application potential in the field of spintronics. Among them, spintronics, as an emerging interdisciplinary discipline, aims to use the spin of electrons rather than charge to achieve information storage and processing.

[0003] However, traditional ferromagnetic materials have problems such as difficult magnetization direction control and unsatisfactory transport properties, which limit their application in spintronics. Currently, certain degrees of magnetic control can be achieved for ferromagnetic materials by means of magnetic fields, electric fields, strain, constructing heterojunctions, etc. to obtain ideal spin transport properties. However, these traditional spin manipulation methods usually have the problems of high energy consumption and volatility. When the external manipulation methods used to achieve the ideal state are withdrawn, an ideal state such as a half-metal bandgap cannot be preserved for a long time and requires continuous external control. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a non-volatile memory device based on a Cr2Cl3S3 / Ga2O3 heterostructure, a construction method, and an application thereof, which solves the problems in the prior art.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A construction method of a non-volatile memory device based on a Cr2Cl3S3 / Ga2O3 heterostructure includes the following steps:

[0007] Build a single layer of Cr2Cl3S3 and a single layer of Ga2O3;

[0008] Stack the single layer of Cr2Cl3S3 and the single layer of Ga2O3 to build two types of Cr2Cl3S3 / Ga2O3 heterostructures;

[0009] Use the two types of Cr2Cl3S3 / Ga2O3 heterostructures to construct a non-volatile memory device based on a Cr2Cl3S3 / Ga2O3 heterostructure.

[0010] Furthermore, when stacking monolayer Cr2Cl3S3 and monolayer Ga2O3, the side of the unit cell Cr2Cl3S3 with Cl atoms is selected to be close to the 2×2×1 supercell Ga2O3 for stacking, obtaining the Cr2Cl3S3 / Ga2O3 van der Waals heterojunction. Ga2O3 is a five-atom layer structure connected in the order of O–Ga–O–Ga–O. By changing the relative position of the middle O atom layer, the direction of ferroelectric polarization can be reversed.

[0011] Furthermore, the stacking methods corresponding to the two Cr2Cl3S3 / Ga2O3 heterostructures are as follows:

[0012] 1) When the middle O atom layer is closer to the lower Ga atom layer in the Z-axis direction, the ferroelectric material Ga2O3 is polarized upward, denoted as: Cr2Cl3S3 / P↑-Ga2O3;

[0013] 2) When the middle O atom layer is closer to the upper Ga atom layer in the Z-axis direction, the ferroelectric material Ga2O3 is polarized downward, denoted as: Cr2Cl3S3 / P↓-Ga2O3.

[0014] Furthermore, the process of constructing a non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure is as follows: orthogonalize the two Cr2Cl3S3 / Ga2O3 heterostructures and perform a 3×3×1 supercell operation.

[0015] Furthermore, the lattice parameters of Cr2Cl3S3 and Ga2O3 are and

[0016] The non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure is constructed using the above construction method.

[0017] The above application of the non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure in data storage.

[0018] A computer device includes the above non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure.

[0019] A chip includes the above non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure.

[0020] A server includes the above non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure.

[0021] Advantages of the present invention:

[0022] In the memory constructed by the present invention, by regulating the polarization direction of the ferroelectric (FE) material Ga2O3 through an electric field, a reversible switching of the ferromagnetic (FM) semiconductor Cr2Cl3S3 from the semiconductor state to the half-metal state can be achieved. This process has significant non-volatile characteristics: once the polarization direction is changed, the state (semiconductor or half-metal) of Cr2Cl3S3 will remain unchanged until the next polarization direction is changed. This property is particularly important for storage devices because it allows data to be stored without a continuous electric field, thereby significantly reducing power consumption and improving data stability. Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a schematic diagram of the crystal structure of monolayer Cr2Cl3S3 and monolayer Ga2O3 of the present invention;

[0025] Figure 2 It is a schematic diagram of the Cr2Cl3S3 / Ga2O3 heterostructure and its energy band of the present invention;

[0026] Figure 3 It is a schematic diagram of the structure and related performance of a non-volatile storage device based on the Cr2Cl3S3 / Ga2O3 heterostructure of the present invention. Detailed Embodiments

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0028] A method for constructing a non-volatile storage device based on the Cr2Cl3S3 / Ga2O3 heterostructure includes the following steps:

[0029] S1, construct monolayer Cr2Cl3S3 and monolayer Ga2O3;

[0030] Analyze the band structures of Cr2Cl3S3 and Ga2O3 using the Vienna Ab-initio Simulation Package (VASP); first, import the primitive cell structure files of Cr2Cl3S3 and Ga2O3, and use VASP to calculate their band structures. The electron exchange-correlation potential used in the calculation is PBE-GGA, the plane-wave cutoff energy is set to 600 eV, the Brillouin zone integration grid is 9×9×1, and the force convergence criterion is

[0031] Since Cr2Cl3S3 is a ferromagnetic semiconductor, it is necessary to add the magnetic moment and the U value in the input file. According to the reference, the U value is selected to add 2.8 eV to the 3d orbit of Cr. In addition, considering that both Cr2Cl3S3 and Ga2O3 are ferroelectric materials, a dipole correction parameter is also added in the calculation. Through the analysis of the calculation results, it can be obtained that Cr2Cl3S3 is a ferromagnetic material, which is the same as the relevant literature. The constructed Cr2Cl3S3 and Ga2O3 are respectively as Figure 1 shown in (a) and (b) below. The lattice parameters of Cr2Cl3S3 and Ga2O3 are respectively and where, Figure 1 above and below (a) are respectively the top view and the side view of the crystal structure of Cr2Cl3S3; Figure 1 above and below (b) are respectively the top view and the side view of the crystal structure of Ga2O3.

[0032] The spin-resolved band of monolayer Cr2Cl3S3 is as Figure 1 shown in (c) below. Among them, the red dots and the green dots represent the spin-up band and the spin-down band respectively; it can be seen that neither the spin-up band nor the spin-down band of Cr2Cl3S3 crosses the Fermi level, and Cr2Cl3S3 is a semiconductor material.

[0033] S2, stack monolayer Cr2Cl3S3 and monolayer Ga2O3 to construct the Cr2Cl3S3 / Ga2O3 heterostructure:

[0034] Perform a 2×2×1 cell expansion operation on Ga2O3 to make the lattice mismatch rate between the two only 2.6%, which is much less than 5%, so as to ensure that the heterostructure will not deform. Based on this, two van der Waals heterostructures of Cr2Cl3S3 / Ga2O3 are stacked, which are respectively denoted as: Cr2Cl3S3 / P↑-Ga2O3 and Cr2Cl3S3 / P↓-Ga2O3. As Figure 2 shown in (a) below, the stacking method corresponding to Cr2Cl3S3 / P↑-Ga2O3 is to stack the Cl atom layer of Cr2Cl3S3 on one side with the Ga2O3 with upward polarization after 2×2×1 cell expansion; as Figure 2As shown in (b) of [relevant context], the stacking mode corresponding to Cr2Cl3S3 / P↓-Ga2O3 is to stack the Cl atomic layer side of Cr2Cl3S3 with the polarization-down Ga2O3 after a 2×2×1 supercell.

[0035] Construct different configurations using the ferroelectric polarization directions of the two materials, and calculate the binding energy using the following formula:

[0036] E b = E Cr2Cl3S3 / Ga2O3 - E Cr2Cl3S3 - E Ga2O3

[0037] In the formula, E b is the binding energy, E Cr2Cl3S3 / Ga2O3 is the total energy after the interface between Cr2Cl3S3 and Ga2O3 is formed, E Cr2Cl3S3 is the energy of the individual Cr2Cl3S3 material, and E Ga2O3 is the energy of the individual Cr2Cl3S3 material;

[0038] The binding energies of the Cr2Cl3S3 / Ga2O3 structures under different stackings are shown in Table 1:

[0039] Table 1 Binding energies of Cr2Cl3S3 / Ga2O3 structures under different stackings

[0040] <![CDATA[E b (eV)]]> <![CDATA[Cr2Cl3S3 / P↑-Ga2O3]]> -0.5916600 <![CDATA[Cr2Cl3S3 / P↓-Ga2O3]]> -0.5381820

[0041] It can be seen from the data in Table 1 that the binding energies of both Cr2Cl3S3 / P↑-Ga2O3 and Cr2Cl3S3 / P↓-Ga2O3 are less than 0 eV, ensuring the stability of the heterojunction.

[0042] In this embodiment, all calculations are based on the density functional theory (DFT) in the Vienna Ab-initio Simulation Package (VASP). To accurately describe the electron exchange interaction, the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) functional is adopted. To accurately describe the van der Waals (vdW) interaction, the semi-empirical dispersion correction D3 scheme (DFT-D3) proposed by Grimme is introduced. To ensure sufficient separation between adjacent layers along the c-axis, a vacuum region is introduced. During the structure relaxation process, a 5×5×1 Monkhorst-Pack k-point mesh is used; while in the static self-consistent calculation, density of states (DOS) calculation, and band structure analysis, a 9×9×1 k-point mesh is used. To improve the calculation accuracy, the plane wave cut-off energy is set to 600 eV, and all structures are optimized until the forces and energies converge to and below 0.001 eV. In addition, a Hubbard U value of 2.8 eV is added to the 3d orbitals of Cr, and a dipole correction parameter is added.

[0043] Using the optimized heterojunction structure, the properties of the ferromagnetic state and the antiferromagnetic state are calculated respectively. To fully discuss all possible antiferromagnetic states, three antiferromagnetic states, namely Neel-AFM, stripe-AFM, and zigzag-AFM, are set, and the energy magnitudes of the ferromagnetic state and the antiferromagnetic state are compared. The obtained data results are shown in Table 2, and finally it is determined that the heterojunction is a ferromagnetic semiconductor.

[0044] Table 2 Energy differences between FM and AFM of Cr2Cl3S3 / Ga2O3 structures under different stackings

[0045] ΔFM (eV) ΔnAFM (eV) ΔsAFM (eV) ΔzAFM (eV) <![CDATA[Cr2Cl3S3 / P↑-Ga2O3]]> 0 2.85718 1.81033 0.81918 <![CDATA[Cr2Cl3S3 / P↓-Ga2O3]]> 0 2.77192 1.82599 0.78009

[0046] Further calculate its self-consistent band structure, as Figure 2 shown; among them, Figure 2 (c) and (d) in are the spin-up band and the spin-down band of Cr2Cl3S3 / P↑-Ga2O3 respectively. It can be seen that the spin-up band of Cr2Cl3S3 / P↑-Ga2O3 crosses the Fermi level, while the spin-down band does not cross the Fermi level, and the Cr2Cl3S3 / P↑-Ga2O3 heterojunction exhibits half-metallicity.

[0047] Figure 2 (e) and (f) in are the spin-up band and the spin-down band of Cr2Cl3S3 / P↓-Ga2O3 respectively; it can be seen that neither the spin-up nor the spin-down band of Cr2Cl3S3 / P↓-Ga2O3 crosses the Fermi level, and the Cr2Cl3S3 / P↓-Ga2O3 heterojunction exhibits semiconductivity.

[0048] Since the structure Cr2Cl3S3 / P↑-Ga2O3 is a half-metal, while the structure Cr2Cl3S3 / P↓-Ga2O3 maintains semiconductor characteristics, it is therefore analyzed that by regulating the ferroelectric polarization direction, the transformation from a ferromagnetic semiconductor to a ferromagnetic half-metal can be achieved.

[0049] S3, construct a non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure;

[0050] To avoid differences in calculations by different software, the two structures optimized by VASP are further used to perform band calculations by combining the density functional theory and the non-equilibrium Green's function method with the calculation software Quantum ATK. The same parameter settings as in VASP are maintained in the calculation, that is, the cutoff energy is 600 eV, and the force and energy converge to and below 0.001 eV, with a Hubbard U value of 2.8 eV added to the 3d orbitals of Cr. In the Initial State of the Cr atom, set the Spin Type to linear, the Scaled Spin to 1, and use the SG15 pseudo potential. The calculation results show that the band structure is basically consistent with the VASP calculation results. The structure Cr2Cl3S3 / P↑-Ga2O3 is still a half-metal, while Cr2Cl3S3 / P↓-Ga2O3 maintains semiconductor characteristics;

[0051] Orthogonalize the two structures (the Cr2Cl3S3 / P↑-Ga2O3 heterostructure and the Cr2Cl3S3 / P↓-Ga2O3 heterostructure) with the VASP structure optimization completed, and perform a 3×3×1 supercell operation to construct an atomic-thickness multiferroic memory as shown in (a) of Figure 3 (i.e., a non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure) for high-density data storage, where the two states of "1" and "0" can be achieved through the signal difference generated by magnetoelectric coupling. The data writing process of the multiferroic memory device inherits the advantages of the ferroelectric memory and can be achieved by switching the polarization state; while the data reading depends on the obvious electrical signal generated by magnetoelectric coupling, effectively avoiding the destructive influence of detecting the polarization state in an independent ferroelectric memory. Under the two configurations, calculate and analyze their transmission spectra through the transmission coefficient formula respectively:

[0052]

[0053] Among them, the transmission coefficient τ σ (E) represents the probability that an electron travels from one electrode (the left electrode) through the scattering region to another electrode (the right electrode) at energy E and spin σ. σ represents the spin index, σ =↑ / ↓, ↑ represents the state where the material has spin up, and ↓ represents the state where the material has spin down. Γ L and Γ R are the coupling matrices of the left and right electrodes respectively, represents the response of the system to the initial excitation, represents the response of the system to the final state, and Tr sums over all possibilities.

[0054] Taking the hole-stacked Cr2Cl3S3 / Ga2O3 heterostructure device as an example, the spin-dependent transport spectrum at zero bias was calculated. As shown in (b) of Figure 3 , for the Ga2O3 polarization state P↑, due to the half-metal property of the heterostructure, there is a significant transmission coefficient near the Fermi level in the spin-up channel; while as shown in Figure 3As shown in (c) therein, the transmission coefficient of the spin-down channel is almost zero, thus achieving a spin polarization transmittance close to 100%. On the contrary, when the polarization state of Ga2O3 is switched to P↓, the semiconductor characteristics of the heterostructure make the transmission coefficients of the spin-up and spin-down channels near the Fermi level almost zero. It can be seen that such a multiferroic device exhibits an obvious valve effect: when the polarization state is P↑, current is allowed to flow through the device; while when the polarization state is P↓, the current is cut off.

[0055] In the description of this specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. 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 present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0056] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A method for constructing a non-volatile memory device based on a Cr2Cl3S3 / Ga2O3 heterostructure, characterized in that, Including the following steps: Construct a single-layer Cr2Cl3S3 and a single-layer Ga2O3; Stack the single-layer Cr2Cl3S3 and the single-layer Ga2O3 to construct two types of Cr2Cl3S3 / Ga2O3 heterostructures; Utilize the two types of Cr2Cl3S3 / Ga2O3 heterostructures to construct a non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure.

2. The construction method of the non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure according to claim 1, characterized in that, When stacking the single-layer Cr2Cl3S3 and the single-layer Ga2O3, select the side of the unit cell Cr2Cl3S3 with Cl atoms to be close to the 2×2×1 supercell Ga2O3 for stacking to obtain a Cr2Cl3S3 / Ga2O3 van der Waals heterojunction. Ga2O3 is a five-atom layer structure connected in the order of O–Ga–O–Ga–O. By changing the relative position of the middle O atom layer, the direction of ferroelectric polarization is reversed.

3. The construction method of the non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure according to claim 1, characterized in that, The stacking methods corresponding to the two types of Cr2Cl3S3 / Ga2O3 heterostructures are as follows: 1) When the middle O atom layer is closer to the lower Ga atom layer in the Z-axis direction, the ferroelectric material Ga2O3 is polarized upward, denoted as: Cr2Cl3S3 / P↑-Ga2O3; 2) When the middle O atom layer is closer to the upper Ga atom layer in the Z-axis direction, the ferroelectric material Ga2O3 is polarized downward, denoted as: Cr2Cl3S3 / P↓-Ga2O3.

4. The method for constructing a non-volatile memory device based on a Cr2Cl3S3 / Ga2O3 heterostructure according to claim 1, characterized in that, The process of constructing a non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure is: orthogonalize the two types of Cr2Cl3S3 / Ga2O3 heterostructures and perform a 3×3×1 supercell operation.

5. The construction method of the non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure according to claim 1, characterized in that, The lattice parameters of Cr2Cl3S3 and Ga2O3 are and 6. A non-volatile memory device based on a Cr2Cl3S3 / Ga2O3 heterostructure, characterized in that, Constructed by using the construction method described in any one of claims 1-5.

7. Application of the non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure described in claim 6 in data storage.

8. A computer device, characterized in that, Including the non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure described in claim 6.

9. A chip, characterized in that, Including the non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure described in claim 6.

10. A server, characterized in that, Including the non-volatile memory device based on the Cr2Cl3S3 / Ga2O3 heterostructure described in claim 6.

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