Graphene conformal fitting-oriented patterned paper-cut structure and design method thereof

Abstract

The invention discloses a graphene conformal fitting-oriented patterned paper-cut structure and a design method thereof. The design method comprises the following steps: S1, simulating adhesion deformation of a graphene film on the surface of a target substrate with a non-zero Gaussian curvature by adopting a full-atom molecular dynamics method; s2, extracting atomic distribution of an adhesion fitting configuration according to a simulation result of the step S1, and quantitatively calculating the adhesion conformal degree of the graphene film; and S3, designing paper-cut cutting patterns of various graphene films, repeating the steps S1 to S2 until the designed paper-cut cutting patterns reach the target adhesion conformal degree, and taking the patterns as the final patterned paper-cut structure for graphene conformal lamination. According to the method, on the premise that the overall continuity of the graphene is not remarkably damaged, highly conformal attachment of the graphene on a spherical surface and other non-zero Gaussian curvature substrates can be achieved, and therefore the adhesiveness and stability of the film and the substrates are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of two-dimensional nanometer film materials, and particularly relates to a patterned paper-cut structure for conformal attachment of graphene and a design method thereof. BACKGROUND

[0002] In recent years, with the progress of nanometer science and technology, micro-nano materials represented by graphene and other two-dimensional film materials have wide application prospects in the construction of high-performance functional or structural materials and micro-nano mechanical systems. Since the discovery of graphene, it has been explored for designing advanced functional devices, such as field emission devices, nano switches, sensors, flexible electronics, and the like, due to its unique physical and mechanical properties compared to traditional functional materials. However, graphene films need to be adhered to a substrate to suppress the intrinsic wrinkles of independent graphene films. Regardless of the device application, the interface characteristics of the graphene film and the supporting substrate will affect the performance of the functional device, and the adhesion topography will also have a significant impact on the electrical and mechanical properties of the device itself.

[0003] In practice, the supporting substrate surface of the graphene film has rough topography of different scales. The adhesion and attachment of the graphene film on the rough substrate is an important interface mechanics problem. Regarding the influence of the rough substrate surface on the adhesion and attachment behavior of graphene, most current research focuses on one-dimensional sinusoidal, rectangular groove and other developable shapes of the substrate. However, in reality, the substrate surface may have local protrusions and other non-developable topographies with non-Gaussian curvature, and the substrate itself may also have a certain non-Gaussian curvature, and the roughness may even be comparable to the size of the graphene film.

[0004] Efficiently attaching graphene films to target substrate surfaces with non-zero Gaussian curvature (such as spherical surfaces) has been a key technical challenge for a long time. Traditional methods include hot pressing, solution transfer, and soft template-assisted transfer, which can achieve the attachment of graphene in local areas to some extent, but the overall attachment is not good, and problems such as wrinkling, warping, hanging, and cracking often occur, which greatly limits the application of graphene in complex curved surface devices. Therefore, there is an urgent need for a controllable structure design strategy to improve the adhesion and conformal ability of graphene films on substrates with non-zero Gaussian curvature, thereby improving the overall stability and performance of the device. SUMMARY

[0005] In view of the above problems, the present application aims to provide a patterned paper-cut structure for conformal attachment of graphene and a design method thereof.

[0006] The technical solution of the present application is as follows: On the one hand, a design method of a patterned paper-cut structure for conformal attachment of graphene is provided, comprising the following steps: S1: Adhesion deformation of graphene film on a target substrate surface with non-zero Gaussian curvature is simulated by all-atom molecular dynamics method; S2: Atomic distribution of adhesion conformal configuration is extracted according to the simulation result of step S1, and adhesion conformal degree of graphene film is quantitatively calculated; S3: A plurality of paper-cutting cutting patterns of graphene film are designed, steps S1-S2 are repeated until the designed paper-cutting cutting pattern reaches the target adhesion conformal degree, and the pattern is taken as the final patterned paper-cutting structure for graphene conformal adhesion.

[0007] As preferred, in step S1, modeling and molecular dynamics simulation are performed by using molecular dynamics simulation software.

[0008] As preferred, the molecular dynamics simulation software uses LAMMPS software.

[0009] As preferred, in step S1, the target substrate with non-zero Gaussian curvature uses a spherical silicon substrate.

[0010] As preferred, in step S2, the adhesion conformal degree is calculated by the following formula: (1) In the formula, C is the adhesion conformal degree; n conform is the total number of carbon atoms in the conformal part; n initial is the total number of carbon atoms in the initial state of the graphene film; The total number of carbon atoms in the conformal part is obtained by the following steps: First, the interatomic distance between the carbon atoms of the graphene film and the element atoms of the substrate is calculated by the following formula: (2) In the formula, d fg is the interatomic distance between the carbon atom f of the graphene film and the element atom g of the substrate; x f , y f , z f are the three-dimensional coordinates of the carbon atom f of the graphene film; x g , y g , z g are the three-dimensional coordinates of the element atom g of the substrate; Then, it is judged whether the interatomic distance is less than or equal to the target interatomic distance. If yes, the graphene film carbon atom is marked as a conformal part; Finally, all atoms are traversed to obtain the total number of carbon atoms in the conformal part.

[0011] As preferred, when the target substrate is a silicon substrate, the target interatomic distance is 6 angstroms.

[0012] As preferred, in step S3, when designing the cutting pattern, if the target substrate with non-zero Gaussian curvature is a spherical substrate, a circular graphene film is adopted, slits are introduced along the radial direction of the circular graphene film, the radial length of the slits is l c , the width of the slits is w, and the circular graphene film is cut M times along the circumferential direction at equal angles, and the rotation angle between adjacent slits is 360° / M.

[0013] As preferred, the width of the slits needs to satisfy the following conditions: (3) (4) In the formula: is the change amount of the circumference of the film in the equilibrium configuration; r is the radius of the circular graphene film; R sub is the radius of the spherical substrate.

[0014] As preferred, the width of the slits w is taken as .

[0015] On the other hand, the application also provides a patterned cutting structure for graphene conformal attachment, which is designed by using the design method of the patterned cutting structure for graphene conformal attachment according to any one of the above.

[0016] The application has the following beneficial effects: The application realizes the highly conformal attachment of graphene on a spherical surface or other substrates with non-zero Gaussian curvature by introducing a controllable two-dimensional cutting pattern, without significantly damaging the overall continuity of graphene, thereby significantly improving the adhesion and stability of the film and the substrate. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0018] Figure 1 The flowchart for calculating the conformal degree of graphene film adhesion; Figure 2 The cutting design schematic diagram of graphene film in one specific embodiment; Figure 3 The molecular dynamics model schematic diagram of graphene film-spherical surface silicon substrate in one specific embodiment; Figure 4 The energy change and the change process of the film configuration with the molecular simulation time step in the graphene film adhesion conformal process in one specific embodiment; Figure 5 Fig. 3 is a schematic diagram of the variation of the adhesive conformal degree of a non-cut graphene film on a spherical substrate with geometric size in one specific embodiment; wherein A is the radius R of the spherical substrate sub Fig. 4 is the equilibrium adhesive configuration of graphene films with different radii R of 20 nm, B is the radius R of the spherical substrate sub Fig. 5 is the variation of the conformal degree C of graphene films with different radii R of 10 nm, 15 nm and 20 nm with the radius ratio r / R sub Figure 6 Fig. 6 is a schematic diagram of a molecular dynamics model of a cut graphene-spherical substrate in one specific embodiment; Figure 7 Fig. 7 is a schematic diagram of the wrinkle situation of different cutting times in one specific embodiment; Figure 8 Fig. 8 is a schematic diagram of the adhesive state and conformal degree of cut graphene with different cutting times and cutting lengths in one specific embodiment; Figure 9 Fig. 9 is a schematic diagram of the quantitative relationship between the adhesive conformal degree and the cutting times M and the cutting length l in one specific embodiment. c DETAILED DESCRIPTION

[0019] The present application will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments in the present application and the technical features in the embodiments can be combined with each other without conflict. It should be noted that all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs, unless otherwise specified. The present application discloses that the "including" or "containing" and similar words mean that the elements or objects before the word cover the elements or objects listed after the word and their equivalents, and do not exclude other elements or objects.

[0020] In one aspect, the present application provides a design method of a patterned cut paper structure for graphene conformal fitting, comprising the following steps: S1: using a full-atom molecular dynamics method to simulate the adhesive deformation of a graphene film on a target substrate surface with a non-zero Gaussian curvature.

[0021] In one specific embodiment, a molecular dynamics simulation software is used for modeling and molecular dynamics simulation. Optionally, the molecular dynamics simulation software uses LAMMPS software.

[0022] ​​In one specific embodiment, the target substrate with non-zero Gaussian curvature adopts a spherical silicon substrate. It should be noted that the spherical non-zero Gaussian curvature structure is a relatively common substrate structure, and in addition to this structure, other non-zero Gaussian curvature structures such as hyperboloid and concave-convex polyhedron in the prior art can also be applicable to the present application.

[0023] S2: Extracting the atomic distribution of the adhesion conformal configuration according to the simulation result of step S1, and quantitatively calculating the adhesion conformal degree of the graphene film.

[0024] In one specific embodiment, as shown in Figure 1 the adhesion conformal degree is calculated by the following formula: (1) In the formula, C is the adhesion conformal degree; n conform is the total number of carbon atoms in the conformal part; n initial is the total number of carbon atoms in the initial state of the graphene film; The total number of carbon atoms in the conformal part is obtained by the following steps: First, the interatomic distance between the carbon atoms of the graphene film and the element atoms of the substrate is calculated by the following formula: (2) In the formula, d fg is the interatomic distance between the carbon atom f of the graphene film and the element atom g of the substrate; x f , y f , z f are the three-dimensional coordinates of the carbon atom f of the graphene film; x g , y g , z g are the three-dimensional coordinates of the element atom g of the substrate; Then, it is judged whether the interatomic distance is less than or equal to the target interatomic distance. If yes, the graphene film carbon atom is marked as a conformal part; Finally, all atoms are traversed to obtain the total number of carbon atoms in the conformal part.

[0025] In one specific embodiment, when the target substrate is a silicon substrate, the target interatomic distance is 6 angstroms.

[0026] S3: Designing various paper-cutting patterns of graphene films, repeating steps S1-S2 until the designed paper-cutting pattern reaches the target adhesion conformal degree, and taking this pattern as the final patterned paper-cutting structure for graphene conformal adhesion.

[0027] The wrinkles will reduce the conformality of the graphene film, and the wrinkles are caused by geometric incompatibility. In the case of non-full conformality, the wrinkles generally appear at the edge of the film and extend along the radial direction. The paper-cutting technology is a subtractive method, which realizes the structural flexibility by cutting and hollowing the plane material. The paper-cutting design idea is introduced into the graphene film in the application, and the molecular dynamics simulation is used for research, so that the adhesion conformality between the graphene film and the substrate with non-zero Gaussian curvature is enhanced.

[0028] In a specific embodiment, as shown in Figure 2 , when designing the paper-cutting pattern, if the target substrate with non-zero Gaussian curvature is a spherical substrate, a circular graphene film is used, a slit is introduced along the radial direction of the graphene film, the radial length of the slit is l c , the width of the slit is w, and M times of cutting is performed along the ring direction at equal angles, and the rotation angle between adjacent slits is 360° / M.

[0029] In a specific embodiment, the width of the slit needs to satisfy the following condition: (3) (4) In the formula: is the change amount of the circumference of the film in the equilibrium configuration; r is the radius of the circular graphene film; R sub is the radius of the spherical substrate.

[0030] When the formula (3) is equal, the material damage of the graphene film is the smallest; in order to minimize the material loss of the graphene film, the width of the slit w is taken as .

[0031] When the formula (3) is not satisfied, the edge part of the graphene film will overlap after conforming, so when designing the paper-cutting pattern, the width of the slit needs to satisfy the condition of the formula.

[0032] On the other hand, the application also provides a patterned paper-cut structure for graphene conformal fitting, which is designed by using the design method of the patterned paper-cut structure for graphene conformal fitting according to any one of the above.

[0033] In a specific embodiment, taking a spherical silicon substrate as an example, the pattern of the graphene film is designed by using the design method of the patterned paper-cut structure for graphene conformal fitting according to the application.

[0034] In this embodiment, the open source molecular dynamics simulation software LAMMPS is used for modeling and molecular dynamics simulation, and OVITO is used for visualization processing.

[0035] The molecular dynamics model of the graphene film-spherical substrate adhesion is shown in the accompanying Figure 3Graphene film and spherical silicon substrate were constructed by Atomsk. The lattice constant of silicon substrate is 5.431 A, and the unit cell is a cubic cell with diamond structure. The outer diameter of the silicon substrate is 20 nm. The lattice constant of graphene is 0.246 nm, and each carbon atom forms a covalent bond with three surrounding carbon atoms.

[0036] Since the distance between carbon atoms and silicon atoms is greater than 10 A, the interaction between them is very small. Reduce the thickness of the substrate without affecting the final result, that is, establish a hollow spherical cap with a thickness greater than 10 A, thereby reducing the amount of calculation.

[0037] The unit is set to the metal system. The x, y, and z directions are set to non-periodic boundary conditions. Verlet algorithm is used for time integration, and the time step is set to 1 femtosecond.

[0038] The carbon atoms in the graphene film interact through the AIREBO potential, and the silicon atoms in the substrate interact through the TERSOFF potential. The interaction between the two atoms is described by the 12-6 Lennard-Jones potential function (zero potential equilibrium distance is 4.0669 A, potential well depth is 0.00428 eV), and the cutoff distance is 10.0 A, which better represents the van der Waals interaction between graphene and the substrate.

[0039] The film keeps the x and y coordinates of the center of mass unchanged and can move and deform in the z direction, while the substrate atoms are fixed. Initially, the distance between the film and the substrate is set to 20 A, and the carbon atoms in the film and the silicon atoms in the substrate have little interaction due to the distance greater than the cutoff distance.

[0040] The NVT ensemble is used, and the initial temperature of the system is set to 1 K. The graphene film is moved as a whole to be within the Lennard-Jones potential cutoff distance, and the interaction with the substrate atoms begins, while the substrate atoms are still in a rigid fixed state. Due to the influence of the interaction between the film atoms and the substrate atoms, the graphene film moves towards the substrate until it is fully relaxed and reaches an equilibrium configuration. The total energy difference between the initial state and the fully relaxed state gives the sum of the graphene adhesion energy, tensile energy, and bending energy.

[0041] After the simulation is completed, the output data dump file is imported into the OVITO visualization software, and the deformation process of the graphene film and the fully relaxed adhesion configuration are observed. As Figure 4 shown, the adhesion system has reached a stable state at 200,000 steps.

[0042] The molecular dynamics simulation outputs a file containing the atom types, atom numbers, and atom coordinates in the equilibrium adhesion state. The atom types, atom numbers, and atom coordinates are then imported into MATLAB. For each carbon atom f in the graphene film, all substrate silicon atoms g are traversed, and the interatomic spacing d... fg If the carbon atom label of the graphene film is ≤6 Å, then the carbon atom label of the graphene film is stored in the conformal portion. The adhesion conformity of the graphene film is calculated by equation (1). The adhesion conformity of the uncut graphene film on the spherical substrate varies with the geometric dimensions as follows: Figure 5 As shown.

[0043] from Figure 5 It can be seen that when the radius (r) of the graphene film is equal to the radius (R) of the spherical substrate... sub The ratio of r / R sub When the radius is less than 0.4, the graphene film is in the fully conformal stage. As the radius of the graphene film increases, wrinkles form, causing the conformity degree C to continuously decrease. The conformity degree C increases with r / R. sub The trend is roughly linearly decreasing. When the graphene radius is smaller than the substrate radius, the conformality of the film is greater than 75%. A paper-cutting pattern is designed using a graphene film radius of r = 14 nm, and the seam width w is taken as... .

[0044] Molecular dynamics model of paper-cut graphene-spherical substrate as follows Figure 6 As shown, the folds appear as follows with different cutting counts. Figure 7 As shown, the adhesion state and conformity results for different cutting times and different radial lengths are as follows: Figure 8 As shown, the quantitative relationship between the degree of conformal adhesion and the number of cuts M and the seam length lc is as follows: Figure 9 As shown.

[0045] from Figure 7 It can be seen that the degree of conformity increases with the increase of the number of cuttings M and the seam length l. c As the length increases, the wrinkles also increase. If the number of cuts is too small, wrinkles will appear not only at the cut but also at the intact edges; when the cut length is long enough and the number of cuts is large enough, the wrinkles in the graphene film will be eliminated.

[0046] from Figure 8 It can be seen that for a tailor's length of l c Graphene cut to 8nm diameter can achieve complete conformality when cut twice or more. When the seam length is l... c At a thickness of 4nm, all graphene cuts exhibited wrinkles, but the degree of conformal adhesion increased with the number of cuts. When uncut, the conformal degree of the graphene film was 86.53%, and the seam length l cThe conformality of the cut graphene with a cutting length of 4 nm and a cutting number of M = 2 is more than 90%. When M = 8, the conformality reaches about 97%.

[0047] Figure 9 In the figure, the blue lines are the contour lines of the conformality of 99.5% fitted by the data, and when the conformality is greater than or equal to 99.5%, the graphene and the spherical substrate are considered to be completely conformal. From the figure, it can be seen that the more the cutting number is, and the longer the cutting length is, the higher the adhesive conformality is. Figure 9 It can be seen that the more the cutting number is, and the longer the cutting length is, the higher the adhesive conformality is. Through the simulation, the cutting pattern design scheme of the graphene can be obtained. Figure 9 It can guide the cutting pattern design scheme of the graphene to obtain a larger adhesive conformality. If the graphene film is completely adhered to the spherical substrate, the cutting length needs to be at least 7 nm. When the cutting length is 8 nm, the cutting number needs to be 5 to achieve complete conformality, and the cutting number does not need to be 6 or even 8. Further constraint programming method can further consider reducing material loss and cutting number to achieve the target conformality.

[0048] It should be noted that the above-mentioned embodiment of the present application is only a preferred embodiment of the present application, and the long and wide form of the cutting used is only a general cutting design idea. The design concept and simulation method are also applicable to other forms of paper-cut structure, such as grid-shaped, scale-shaped and other two-dimensional paper-cut pattern design. These patterns will also help to improve the conformality of graphene on the non-zero Gaussian curvature substrate.

[0049] The molecular dynamics simulation framework and the index system for quantitatively calculating the adhesive conformality of the present application have good universality and reference value, and can provide theoretical support and method guidance for the paper-cut design and performance optimization of other two-dimensional nanomaterials.

[0050] In actual operation, the cutting of graphene can be realized through laser etching, focused ion beam etching and other technologies according to the designed paper-cut pattern. In addition, the path of cutting and transferring can also be used to realize the overall transfer and conformal attachment of the paper-cut pattern.

[0051] The above-mentioned is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above-mentioned disclosed technical content without departing from the scope of the technical solution of the present application to obtain equivalent embodiments with equivalent changes. Any simple modification, equivalent change and modification made to the above-mentioned embodiments according to the technical essence of the present application still belongs to the scope of the technical solution of the present application.

Claims

1. A design method for patterned paper-cut structures oriented towards graphene conformal bonding, characterized in that, Includes the following steps: S1: The adhesion and deformation of graphene films on a target substrate surface with non-zero Gaussian curvature were simulated using all-atom molecular dynamics. S2: Extract the atomic distribution of the adhesion and bonding configuration based on the simulation results of step S1, and quantitatively calculate the degree of adhesion conformity of the graphene film. S3: Design various paper-cutting patterns for graphene films, repeat steps S1-S2 until the designed paper-cutting patterns achieve the target degree of conformal adhesion, and use this pattern as the final patterned paper-cutting structure for conformal bonding to graphene.

2. The design method for patterned paper-cut structures oriented towards graphene conformal bonding according to claim 1, characterized in that, In step S1, molecular dynamics simulation software is used for modeling and molecular dynamics simulation.

3. The design method for patterned paper-cut structures oriented towards graphene conformal bonding according to claim 2, characterized in that, The molecular dynamics simulation software used is LAMMPS.

4. The design method for patterned paper-cutting structures oriented towards graphene conformal bonding according to claim 1, characterized in that, In step S1, the target substrate with non-zero Gaussian curvature is a spherical silicon substrate.

5. The design method for patterned paper-cut structures oriented towards graphene conformal bonding according to claim 1, characterized in that, In step S2, the degree of adhesion conformity is calculated using the following formula: （1） In the formula: C represents the degree of conformal adhesion; n conform n represents the total number of carbon atoms in the conformal portion. initial This represents the total number of carbon atoms in the initial state of the graphene film. The total number of carbon atoms in the conformal portion is obtained through the following steps: First, the interatomic distance between carbon atoms in the graphene film and atoms in the substrate element is calculated using the following formula: （2） In the formula: d fg x represents the interatomic distance between carbon atoms f in the graphene film and atoms g in the substrate element; f y f z f Let x be the three-dimensional coordinates of a carbon atom f in the graphene film; g y g z g Let g be the three-dimensional coordinates of the atom g, which is the base element. Then determine whether the interatomic spacing is less than or equal to the target interatomic spacing. If so, mark the carbon atoms of the graphene film as conformal portions. Finally, by iterating through all atoms, the total number of carbon atoms in the conformal portion is obtained.

6. The design method for patterned paper-cut structures oriented towards graphene conformal bonding according to claim 5, characterized in that, When the target substrate is a silicon substrate, the target atomic spacing is 6 Å.

7. The design method for patterned paper-cutting structures oriented towards graphene conformal bonding according to claim 1, characterized in that, In step S3, when designing the paper-cutting pattern, if the target substrate with non-zero Gaussian curvature is a spherical substrate, a circular graphene film is used, and a seam is introduced along its radial direction, with a seam radial length of l. c The seam width is w, and the seams are cut M times at equal angles along the circumference. The rotation angle between adjacent seams is 360° / M.

8. The design method for patterned paper-cut structures oriented towards graphene conformal bonding according to claim 7, characterized in that, The seam width must meet the following conditions: （3） （4） In the formula: R is the change in film perimeter at equilibrium configuration; r is the radius of the circular graphene film; sub Let be the radius of the spherical base.

9. The design method for patterned paper-cut structures oriented towards graphene conformal bonding according to claim 8, characterized in that, The width of the tailor, w, is taken as .

10. A patterned paper-cutting structure for conformal bonding with graphene, characterized in that, It was designed using the patterned paper-cut structure design method for conformal bonding to graphene as described in any one of claims 1-9.

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