Superlattice structure for realizing electronic structure transformation and splicing construction method thereof

Abstract

The invention discloses a superlattice structure for realizing electronic structure transformation and a splicing construction method thereof, relates to the field of spintronics, and realizes the electronic structure property transformation of semimetal property, semiconductor property and metal property through three superlattice structures with different configurations. A novel nanobelt superlattice structure is designed on the basis of a transverse and longitudinal splicing structure mode, and on the basis of adopting a transition metal disulfide material and transverse and longitudinal structure design, electronic structure conversion from semimetal to semiconductor to metal can be achieved only through different periodic unit cell splicing modes. Therefore, a theoretical guidance scheme is provided for subsequent design of a nanobelt system of which the electrical properties are easy to regulate and control, and development and application of related devices are further promoted.

Description

Technical Field

[0001] The present invention relates to the field of spin electronics, and in particular to a superlattice structure for realizing electronic structure transformation and a splicing construction method thereof. Background Art

[0002] In the device application of semiconductor materials, people often achieve effective regulation of the electronic structure of materials through doping, electric field, stress or light excitation. For tungsten disulfide, people have found that the transition from semiconductor to metal can be achieved by adjusting the type and concentration of dopants. For zinc oxide, the free transition from semiconductor to metal can be achieved by irradiating light of a specific wavelength and a certain intensity. However, the above methods rely on complex external conditions and uncontrollable factors, such as control of doping concentration, obvious structural distortion and complex production processes. Therefore, exploring simple and efficient means of electronic structure regulation has always been the focus of attention.

[0003] Compared with methods such as doping or photoexcitation, the superlattice structure avoids problems such as lattice defects or impurity scattering introduced by impurities, and does not require complex external conditions. It is expected to be a feasible means of electronic structure regulation. Summary of the invention

[0004] In view of the above-mentioned deficiencies of the prior art, the present invention provides a superlattice structure and a splicing construction method for realizing electronic structure transformation. Based on superlattice structures of different periods, superlattice structures based on different periods in the same transition metal disulfide horizontal and vertical splicing material are designed to realize flexible transformation of electronic structure properties.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] A method for splicing and constructing a superlattice structure for realizing electronic structure transformation comprises the following steps:

[0007] S1: Assuming that the extension direction of the nanobelt is the y-axis direction, 2n MX2 primitive cells are sequentially spliced ​​along the x-axis direction to construct a structural unit A; the metal atom M is one of molybdenum, tungsten or chromium, and the chalcogen atom X is one of sulfur, selenium or tellurium;

[0008] S2: n NY2 primitive cells and n N'Y'2 primitive cells are sequentially spliced ​​along the x-axis direction to construct a structural unit B; N and N' are any one of molybdenum, tungsten or chromium, Y and Y' are any one of sulfur, selenium or tellurium; and N and N' and Y and Y' cannot be the same at the same time;

[0009] S3: Structural unit A and structural unit B are spliced ​​in parallel to obtain a superlattice structure, including three configurations: AB, ABA and BAB. Several superlattice structures of the same configuration are extended and spliced ​​in the y-axis direction to obtain a nanobelt;

[0010] Among them, the nanobelts obtained by extending and splicing the AB-configuration superlattice structure have semi-metallic properties, the nanobelts obtained by extending and splicing the ABA-configuration superlattice structure have semiconductor properties, and the nanobelts obtained by extending and splicing the BAB-configuration superlattice structure have metallic properties.

[0011] Furthermore, step S1 is specifically as follows:

[0012] S101: Obtain the hexagonal unit cell of the NX2 crystal from the relevant database, import it into the software for sectioning, reconstruct the lattice angle to 90°, and obtain the minimum rectangular structural unit of the NX2 crystal;

[0013] S102: Let the extension direction of the superlattice structure be the y-axis direction, and expand the minimum rectangular structure unit obtained in S101 by 2n times along the x-axis direction to obtain a pure rectangular structure unit with a width of 2n;

[0014] S103: Use H atoms and O atoms to passivate both sides of the pure rectangular structural unit respectively to obtain structural unit A.

[0015] Furthermore, step S2 is specifically as follows:

[0016] S201: Obtain the hexagonal unit cells of NY2 and N'Y'2 crystals from the relevant database, import them into the software for sectioning, reconstruct the lattice angle to 90°, and obtain the minimum rectangular structural unit of NY2 crystal and N'Y'2 crystal;

[0017] S202: Let the extension direction of the superlattice structure be the y-axis direction, and expand the minimum rectangular structural units of the NY2 crystal and the N'Y'2 crystal obtained in S101 by n times along the x-axis direction to obtain a first pure rectangular structural unit and a second pure rectangular structural unit with a width of n;

[0018] S203: connecting the first pure rectangular structure unit and the second pure rectangular structure unit along the x-axis to form a transversely spliced ​​rectangular structure unit with a width of 2n;

[0019] S204: Use H atoms and O atoms to passivate both sides of the transversely spliced ​​rectangular structural unit to obtain structural unit B.

[0020] Furthermore, n is an integer greater than or equal to 3.

[0021] Furthermore, the superlattice structures AB, ABA and BAB obtained by splicing the structure unit A and the structure unit B are provided with of vacuum layer.

[0022] The present invention also provides a superlattice structure that realizes electronic structure transformation by adopting the above-mentioned splicing construction method. The superlattice structure spliced ​​horizontally and vertically with three different periods realizes the electronic structure property transformation of semi-metallic properties, semiconductor properties and metallic properties by constructing nanobelts.

[0023] The beneficial effects of the present invention are:

[0024] The present invention designs a new type of nanobelt superlattice structure based on the horizontal and vertical splicing structure. Based on a type of transition metal disulfide material and the horizontal and vertical structure design, the electronic structure transformation from semimetal to semiconductor to metal can be achieved only through different periodic unit cell splicing methods. This will provide a theoretical guidance for the subsequent design of nanobelt systems with easily adjustable electrical properties, thereby promoting the development and application of related devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a superlattice structure for realizing electronic structure transformation in an embodiment;

[0026] Figure 2 Schematic diagram of the minimum rectangular structural unit of the initial MoS2 crystal;

[0027] Figure 3 Schematic diagram of the structure of the structural unit A constructed for MoS2;

[0028] Figure 4 Schematic diagram of the structure of building block B constructed for MoSe2 and WSe2;

[0029] Figure 5 Schematic diagram of the structure of three different periodic horizontal and vertical splicing superlattice structures;

[0030] Figure 6 The band diagrams of three different periodic horizontal and vertical spliced ​​superlattice structures. DETAILED DESCRIPTION

[0031] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0032] In this embodiment, the structural unit A constructed by MoS2 and the structural unit B constructed by MoSe2 and WSe2 are taken as examples. When n is less than 3, the structural unit A and the structural unit B are prone to affect the performance of the superlattice structure. Therefore, n should be greater than or equal to 3. In this embodiment, n=3 is selected to realize the superlattice structure of the electronic structure transformation. Figure 1 As shown, the splicing construction method includes the following steps:

[0033] S1: Construct structural unit A using the software Materials Studio: Assume that the extension direction of the nanobelt is the y-axis direction, and 6 MoS2 primitive cells are sequentially spliced ​​along the x-axis direction to construct structural unit A; specifically:

[0034] S101: Import the hexagonal cell of MoS2 crystal, cut it along the (001) direction, and reconstruct the lattice angle to 90° to obtain the following Figure 2 The smallest rectangular structural unit of the MoS2 crystal shown; Figure 2 a. Figure 2 b is the front view and side view of the minimum rectangular structural unit of the initial MoS2 crystal, in which the blue atoms are Mo atoms and the yellow atoms are S atoms; it is a conventional technique in the art to cut the crystal and reconstruct the surface, so no further description is given;

[0035] S102: expand the rectangular structure unit described in S101 by 6 times along the x-axis direction to obtain a pure rectangular structure unit with a width of 6; S103: passivate the two sides of the pure rectangular structure unit using H atoms and O atoms respectively to obtain a new structure unit A. The selection of passivation atoms refers to the content disclosed in the technology Zheng F, Guo W, Sun S, et al. Tuning the Magnetic and Electronic Properties of Janus MoSSe Nanoribbon by Edge Modification: A First-Principles Study [J]. physica status solidi (b), 2019. DOI: 10.1002 / pssb.201900106., so no further details are given.

[0036] Specifically, the main body of the pure rectangular structural unit of MoS2 is adjusted to be in the middle of the lattice, one Mo atom exposed on one edge is passivated with O atoms, and two S atoms exposed on the other edge are passivated with H atoms to obtain the following: Figure 3 The structural unit A shown, wherein Figure 3 a is the main view of structural unit A, Figure 3 b is a side view of the structural unit A; the red atoms in the figure are O atoms and the white atoms are H atoms.

[0037] S2: 3 MoSe2 primitive cells and 3 WSe2 primitive cells are sequentially spliced ​​along the x-axis direction to construct structural unit B; specifically:

[0038] S201: Obtain MoSe2 and WSe2 rectangular structural units with a width of 3 according to steps S101 and S102;

[0039] S202: connecting the two along the x-axis to form a transversely spliced ​​rectangular structural unit with a width of 2n;

[0040] S203: Use H atoms and O atoms to passivate both sides of the transversely spliced ​​rectangular structural unit to obtain structural unit B.

[0041] In specific implementation, the construction of structural unit B can also be obtained by replacing atoms, specifically: copy the constructed structural unit A, replace half of MoS2 with MoSe2, and replace the other half of MoS2 with WSe2.

[0042] S203: Use H atoms and O atoms to passivate the two sides of the transversely spliced ​​rectangular structural unit to obtain structural unit B. Figure 4 The structural unit B shown, wherein Figure 4 a is the main view of structural unit B, Figure 4 b is a side view of the structural unit B, in which the blue atoms are Mo atoms, the gray atoms are W atoms, the orange atoms are Se atoms, the red atoms are O atoms, and the white atoms are H atoms.

[0043] S3: The superlattice structure is obtained by parallel splicing of the structural unit A and the structural unit B, including three configurations: AB, ABA and BAB, among which: Figure 5 a is the front view of the superlattice structure of AB configuration; Figure 5 b is the front view of the superlattice structure of ABA configuration; Figure 5 c is the front view of the BAB-configured superlattice structure.

[0044] The nanoribbons constructed from the three types of superlattice structures are all zigzag-type nanoribbons.

[0045] Based on the first principle method of density functional theory, the three periodic models (i.e., three superlattice structures) constructed above are used as the basis, and the VASP software package is used for system structure optimization, static self-consistency and energy band calculation. In the calculation process, the exchange correlation functional uses the GGA-PBE functional, and the interaction between electrons and ions is described by the projected augmented wave method. The plane wave cutoff energy is set to 550eV, and the structure optimization is performed under a 1×9×1 k-grid. The self-consistent calculation energy convergence standard is 10 -4eV, when the force on each atom converges to an accuracy less than The optimization was stopped when , and a relatively stable structure was obtained. By analyzing the output structure file, it can be seen that the optimized structure has no obvious changes compared with the previous one, which proves the stability of the structure. A 1×15×1 k-grid was used in the static self-consistent calculation, and the electronic step convergence accuracy was set to 10 -6 eV;

[0046] The energy band calculation is performed using static self-consistent charge density and wave function. The k-point distribution runs through the entire Brillouin zone, and an average of 70 k-points are selected for sampling in each Brillouin zone. The following is obtained: Figure 6 The energy band diagrams of the three configurations shown are given by Figure 6 It can be seen that in the AB configuration, the upper spin state passes through the Fermi level, and the lower spin state has a direct band gap of 0.07eV at the Γ point, showing semi-metallic properties; in the ABA configuration, at the Γ point, the upper and lower spin states have direct band gaps of 0.29eV and 0.07eV, respectively, showing semiconductor properties as a whole; in the BAB configuration, there is no band gap, and both the upper and lower spin states pass through the Fermi level, showing metallic properties as a whole. In general, the electronic structure of the periodic horizontal and vertical splicing system nanoribbons obeys the electronic structure change from semi-metal to semiconductor to metal.

Claims

1. A method for constructing a superlattice structure by splicing to achieve electronic structure transformation, characterized in that: The steps include: S1: Assuming that the extension direction of the nanobelt is the y-axis direction, 2n MX2 primitive cells are sequentially spliced ​​along the x-axis direction to construct a structural unit A; the metal atom M is one of molybdenum, tungsten or chromium, and the chalcogen atom X is one of sulfur, selenium or tellurium; S2: n NY2 primitive cells and n N'Y'2 primitive cells are sequentially spliced ​​along the x-axis direction to construct a structural unit B; N and N' are any one of molybdenum, tungsten or chromium, Y and Y' are any one of sulfur, selenium or tellurium; and N and N' and Y and Y' cannot be the same at the same time; S3: Structural unit A and structural unit B are spliced ​​in parallel to obtain a superlattice structure, including three configurations: AB, ABA and BAB. Several superlattice structures of the same configuration are extended and spliced ​​in the y-axis direction to obtain a nanobelt; Among them, the nanobelts obtained by extending and splicing the AB-configuration superlattice structure have semi-metallic properties, the nanobelts obtained by extending and splicing the ABA-configuration superlattice structure have semiconductor properties, and the nanobelts obtained by extending and splicing the BAB-configuration superlattice structure have metallic properties.

2. The splicing construction method according to claim 1, characterized in that: The step S1 is specifically as follows: S101: Obtain the hexagonal unit cell of the NX2 crystal from the relevant database, import it into the software for sectioning, reconstruct the lattice angle to 90°, and obtain the minimum rectangular structural unit of the NX2 crystal; S102: Let the extension direction of the superlattice structure be the y-axis direction, and expand the minimum rectangular structure unit obtained in S101 by 2n times along the x-axis direction to obtain a pure rectangular structure unit with a width of 2n; S103: Use H atoms and O atoms to passivate both sides of the pure rectangular structural unit respectively to obtain structural unit A.

3. The splicing construction method according to claim 1, characterized in that: The step S2 is specifically as follows: S201: Obtain the hexagonal unit cells of NY2 and N'Y'2 crystals from the relevant database, import them into the software for sectioning, reconstruct the lattice angle to 90°, and obtain the minimum rectangular structural unit of NY2 crystal and N'Y'2 crystal; S202: Let the extension direction of the superlattice structure be the y-axis direction, and expand the minimum rectangular structural units of the NY2 crystal and the N'Y'2 crystal obtained in S101 by n times along the x-axis direction to obtain a first pure rectangular structural unit and a second pure rectangular structural unit with a width of n; S203: connecting the first pure rectangular structure unit and the second pure rectangular structure unit along the x-axis to form a transversely spliced ​​rectangular structure unit with a width of 2n; S204: Use H atoms and O atoms to passivate both sides of the transversely spliced ​​rectangular structural unit to obtain structural unit B.

4. The splicing construction method according to claim 1, characterized in that: The three different periodic horizontal and vertical splicing superlattice structures of AB, ABA and BAB obtained by splicing the structural unit A and the structural unit B, if the extension direction of the superlattice structure is the y-axis direction, then the x-axis and z-axis directions of the superlattice structure are both provided with of vacuum layer.

5. The splicing construction method according to claim 1, characterized in that: n is an integer greater than or equal to 3.

6. A superlattice structure for achieving electronic structure transformation constructed by the splicing construction method according to any one of claims 1 to 5, characterized in that: The three different periodic horizontal and vertical spliced ​​superlattice structures achieve the transformation of electronic structure properties into semi-metallic properties, semiconductor properties and metallic properties by constructing nanobelts.

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