Method for realizing dynamic regulation of molar pattern structure of nanomaterials by off-plane vibration

Abstract

The application discloses a method for realizing dynamic regulation of a moire structure of nanometer material through out-of-plane vibration, and steps are as follows: twisted two-dimensional nanometer material is prepared, the twisted two-dimensional nanometer material is transferred to a substrate structure containing an electrode, and a nanometer resonator with the twisted two-dimensional nanometer material as a vibration component is prepared; a direct current bias voltage and an alternating voltage are applied to the nanometer resonator, so that the two-dimensional resonant cavity generates vibration in a direction perpendicular to the plane, and the two-dimensional resonant cavity generates a stable resonance response by changing the size of the input direct current bias voltage; the frequency and amplitude of the input alternating voltage are changed, so that the amplitude and frequency of the twisted two-dimensional nanometer material are changed, and the moire structure changes continuously when the twisted two-dimensional nanometer material vibrates to a certain amplitude. The method associates the regulation of the moire structure with the out-of-plane vibration of the two-dimensional twisted material, accurately regulates the moire structure by adjusting the size and frequency of the out-of-plane excitation force, and is simple and easy to realize.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of micro / nano electromechanical systems, and particularly relates to a method for dynamically regulating a moire structure of a nano material by out-of-plane vibration. BACKGROUND

[0002] Two-dimensional nanomaterials, such as graphene, black phosphorus, and transition metal dichalcogenides, exhibit excellent mechanical, thermal, optical, electrical, and magnetic properties, and have become typical nanomaterials for constructing key components of nanoelectromechanical systems (NEMS). In recent years, van der Waals materials obtained by stacking two-dimensional nanomaterials exhibit many special physical and chemical properties, and due to their controllable structure and customizable function, they provide an ideal research platform for exploring novel physical phenomena at the nanoscale. In particular, the generation of moire structures in van der Waals materials through interlayer twisting further increases the possibility of regulating the physical properties of van der Waals materials, and has attracted great attention from scientists around the world. Nanoscale "moire engineering" is gradually emerging. Moire structures are superlattice structures formed by slightly mismatched or small-angle relative twisting of different atomic layers. The moire structure of two-dimensional nanomaterials has a significant impact on the electronic, thermal, mechanical, optical, and photoelectric properties of the material. Precise control of the various properties of two-dimensional nanomaterials by dynamically regulating their moire structure will bring technological innovation to the control of micro / nano electromechanical systems (M / NEMS).

[0003] Existing methods for dynamically regulating the moire structure of two-dimensional nanomaterials mainly include:

[0004] 1. Changing the relative twisting angle between layers;

[0005] 2. Mismatching the lattices of different atomic layers by applying in-plane strain such as stretching or compression.

[0006] Due to the limitations of the preparation process of van der Waals materials, it is technically difficult to change the moire structure by directly changing the twisting angle. The method of applying in-plane strain by stretching or compression has the problems of limited structural deformation and difficulty in accurately controlling the in-plane strain in the actual application process. SUMMARY

[0007] In view of the above shortcomings of the prior art, the purpose of the present application is to provide a method for dynamically regulating the moire structure of a nano material by out-of-plane vibration, to solve the problem that it is difficult to dynamically regulate the moire structure in the prior art. The method of the present application associates the regulation of the moire structure with the out-of-plane vibration of the two-dimensional twisted material, and precisely regulates the moire structure by adjusting the size and frequency of the out-of-plane excitation force. The regulation method is simple and easy to implement.

[0008] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] A method for dynamic regulation of moire structure of nanomaterials by out-of-plane vibration according to the present application, the steps are as follows:

[0010] 1) Adopting chemical vapor deposition method and mechanical exfoliation method to prepare twisted two-dimensional nanomaterials, transferring the prepared twisted two-dimensional nanomaterials to a substrate structure containing electrodes, and preparing a nanoresonator with the twisted two-dimensional nanomaterials as the vibration component;

[0011] 2) Applying a direct current bias voltage and an alternating voltage to the nanoresonator, so that the two-dimensional resonant cavity of the nanoresonator produces vibration in the direction perpendicular to the plane, and by changing the size of the input direct current bias voltage, the two-dimensional resonant cavity produces stable resonance response;

[0012] 3) Changing the frequency and amplitude of the input alternating voltage to change the amplitude and frequency of the twisted two-dimensional nanomaterials, and when the twisted two-dimensional nanomaterials reach a certain amplitude of vibration, the moire structure changes continuously (i.e. the interlayer van der Waals potential distribution also changes continuously, which changes various physical properties such as thermal conductivity, band gap, etc.).

[0013] Further, the step 1) specifically includes: preparing single / multi-layer two-dimensional nanomaterials by chemical vapor deposition method, preparing another single / multi-layer two-dimensional material by the same method, and then stacking the two parts of two-dimensional nanomaterials together by mechanical exfoliation and adjusting the twist angle to form twisted two-dimensional nanomaterials, and transferring the prepared twisted two-dimensional nanomaterials to a substrate structure containing electrodes, preparing a nanoresonator on the twisted two-layer two-dimensional nanomaterials by electron beam lithography and metal evaporation process, and finally cleaning the nanoresonator using an oxidizing agent or acid washing method.

[0014] Further, the step 2) specifically includes: numerical modeling according to the size of the nanoresonator, determining the natural frequencies of the nanoresonator by finite element simulation or molecular dynamics simulation, then taking one of the natural frequencies (preferably the first order) as the preset frequency of the input alternating voltage to make the nanoresonator vibrate in the direction perpendicular to the plane (the amplitude of the alternating voltage should not be too large at the beginning, generally a few millivolts), and at the same time, a direct current bias voltage is applied to generate an electric field (the direct current bias voltage needs to be increased slowly from 0 to avoid damage to the nanoresonator, and the size of the direct current bias voltage of the nanoresonator is generally in the order of a few millivolts to a few tens of millivolts), and by adjusting the size of the direct current bias voltage, the nanoresonator reaches the resonance state.

[0015] Further, the step 3) specifically comprises: after reaching the resonant steady state, adjusting the amplitude of the alternating voltage to achieve periodic changes of the moire structure in different degrees, so as to realize continuous adjustment of various physical property parameters of the twisted two-dimensional nanomaterial; then by changing the frequency of the input alternating voltage, taking a frequency different from the natural frequency in step 2), the change frequency of the moire structure is also changed, and then the change frequency of various physical property parameters of the twisted two-dimensional nanomaterial is adjusted.

[0016] Advantages of the present application:

[0017] The present application utilizes the twisted two-dimensional nanomaterial and combines the controllable excitation of the nanoresonator, which can realize accurate dynamic regulation of the moire structure and can be used repeatedly. Compared with the existing method for regulating the moire structure, the present application has the characteristics of high precision, low cost and low operation difficulty, and is suitable for popularization and use in micro-electromechanical systems and nanoelectromechanical systems. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A simple schematic diagram of the nanoresonator exemplified in the method of the present application.

[0019] Figure 2 A schematic diagram of material deformation and moire change.

[0020] Figure 3 A moire change diagram of different excitation forces at different twist angles. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of those skilled in the art, the present application will be further described below in conjunction with the embodiments and the drawings, and the contents mentioned in the embodiments are not limitations of the present application.

[0022] Referring to Figure 1 The method for realizing dynamic regulation of the moire structure of the nanomaterial by out-of-plane vibration of the present application is as follows:

[0023] 1) The twisted two-dimensional nanomaterial is prepared by chemical vapor deposition and mechanical exfoliation method, and the prepared twisted two-dimensional nanomaterial is transferred to a substrate structure containing electrodes to prepare a nanoresonator with the twisted two-dimensional nanomaterial as a vibration component;

[0024] Specifically, the twisted two-dimensional nanomaterial prepared by the chemical vapor deposition method and the mechanical exfoliation method in step 1) is: twisted graphene, twisted molybdenum disulfide or twisted hetero two-dimensional nanomaterial. Taking twisted bilayer graphene as an example, the preparation process is as follows:

[0025] 11) Select a substrate, such as SiO2 or SiC, and prepare a single-crystal metal substrate, such as Ni or Cu, on the surface; the prepared substrate surface is smooth and free of impurities;

[0026] 12) Use chemical vapor deposition (CVD) to deposit a single layer of graphene on the metal (Ni or Cu) surface; place the previously cleaned metal substrate into a CVD reactor, then heat it at high temperature and introduce a precursor gas (such as methane, ethylene, etc.) with high purity and stable concentration, allowing it to decompose and form a single layer of graphene on the metal surface;

[0027] 13) Stack two single layers of graphene together using a mechanical exfoliation method, ensuring that the stacked double-layer graphene surface is flat (without wrinkles, bubbles, damage, etc.) and adjusting the stacking angle to achieve the required twisting of the double-layer graphene, then transfer it to a substrate structure containing electrodes;

[0028] 14) Use micro-nano processing methods (such as lithography and evaporation, etc.) to prepare a nano-resonator of the desired shape, such as a circular plate-shaped nano-resonator, on the twisted double-layer graphene; the prepared nano-resonator is as shown in Figure 1

[0029] 15) Use oxidizing agents and acid washing methods to remove residual organic contaminants and oxide layers.

[0030] In the preferred example, the mechanical exfoliation method in step 13) can use a tape method or an electron beam evaporation method, etc.

[0031] 2) Apply a direct current bias voltage and an alternating voltage to the nano-resonator, causing the two-dimensional resonant cavity of the nano-resonator to vibrate in a direction perpendicular to the plane and produce a stable resonance response by changing the size of the input direct current bias voltage;

[0032] Specifically, the input alternating voltage is a sine wave, U = Asin(ωt), where A is the input alternating voltage amplitude, ω is the alternating voltage frequency, U is the real-time alternating voltage, and t is the time; the stable state response of the two-dimensional resonant cavity is in the form of where X is the real-time amplitude of the two-dimensional resonant cavity, ω0 is the resonant cavity vibration frequency, x is the maximum amplitude, is the phase difference, adjusting the values of A and ω changes the size of x; it should be noted that the preset frequency ω of the input voltage can be obtained through finite element simulation or molecular dynamics simulation, and the intrinsic frequency of the nano-resonator will be different in actual arrangement, so the direct current bias voltage needs to be adjusted to make the intrinsic frequency of the actual material match the preset excitation frequency of the alternating voltage, so as to excite the resonator to resonate and achieve a stable state response.

[0033] ​3) By changing the amplitude A of the input alternating voltage to increase the response amplitude of the nanoresonator, so that the moire structure changes more obviously. In this example, the full-scale excitation force is given to the 10 nm diameter twisted bilayer graphene perpendicular to the plane, and the relationship between the deformation and the moire change is shown in Figure 2 After the nanoresonator reaches a steady-state vibration by changing the amplitude of the alternating voltage, the moire structure will change periodically at a frequency of ω0. Note that when resonating, ω0 will be equal to the preset frequency, and various physical properties of the twisted bilayer graphene will also change periodically at the same frequency. These physical property parameters can be precisely controlled by controlling the amplitude of the alternating voltage. Figure 3 is the moire change of the nanoresonator under different excitation forces at different twist angles.

[0034] In addition, by changing ω and repeating steps 2) and 3), different frequency changes of the moire structure can be achieved, and the frequency of the change of various physical properties of the twisted bilayer graphene can be precisely controlled. When the excitation of the alternating voltage is removed, the resonator returns to its original state for the next use.

[0035] The present application has many specific application approaches, and the above description is only the preferred embodiment of the present application. It should be pointed out that for ordinary skilled persons in the technical field, some improvements can be made without departing from the principles of the present application, and these improvements should also be considered as the protection scope of the present application.

Claims

1. A method for dynamic regulation of moire structure of nanomaterials by out-of-plane vibration, characterized in that, The steps are as follows: 1) twist two-dimensional nanomaterials are prepared by chemical vapor deposition and mechanical exfoliation, and the prepared twist two-dimensional nanomaterials are transferred to a substrate structure containing electrodes to prepare a nanoresonator with twist two-dimensional nanomaterials as a vibrating component; 2) a direct current bias voltage and an alternating voltage are applied to the nanoresonator, so that the two-dimensional resonant cavity of the nanoresonator produces vibration in the direction perpendicular to the plane, and the two-dimensional resonant cavity produces stable resonance response by changing the size of the input direct current bias voltage; 3) change the frequency and amplitude of the input alternating voltage to change the amplitude and frequency of the twist two-dimensional nanomaterials, and when the twist two-dimensional nanomaterials reach a certain amplitude of vibration, the moire structure changes continuously.

2. The method of claim 1, wherein the in-plane vibration is achieved by a piezoelectric actuator. The step 1) specifically comprises: preparing single / multilayer two-dimensional nanomaterials by chemical vapor deposition, preparing another single / multilayer two-dimensional nanomaterials by the same method, and then stacking the two parts of two-dimensional nanomaterials together by mechanical exfoliation and adjusting the twist angle to form twist two-dimensional nanomaterials, and transferring the prepared twist two-dimensional nanomaterials to a substrate structure containing electrodes, preparing a nanoresonator on the twist two-layer two-dimensional nanomaterials by electron beam lithography and metal evaporation process, and cleaning the nanoresonator by using an oxidizing agent or acid washing method.

3. The method of claim 1, wherein the in-plane vibration is applied to the nanomaterial to dynamically control the moire structure of the nanomaterial. The step 2) specifically comprises: numerical modeling according to the size of the nanoresonator, determining the natural frequency of the nanoresonator by finite element simulation or molecular dynamics simulation, then taking one of the natural frequencies as the preset frequency of the input alternating voltage to make the nanoresonator vibrate in the direction perpendicular to the plane, and at the same time, applying a direct current bias voltage to generate an electric field, and adjusting the size of the direct current bias voltage to make the nanoresonator reach a resonance state.

4. The method of claim 3, wherein the in-plane vibration is achieved by a piezoelectric actuator. The step 3) specifically comprises: after reaching a stable resonance state, adjusting the amplitude of the alternating voltage to achieve periodic changes of the moire structure to different degrees, thereby achieving continuous adjustment of various physical property parameters of the twist two-dimensional nanomaterials; then by changing the frequency of the input alternating voltage, taking a frequency different from the natural frequency in step 2), the change frequency of the moire structure also changes, and then the change frequency of the various physical property parameters of the twist two-dimensional nanomaterials is adjusted.

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