Strain field control method for two-dimensional atomic layer material

Abstract

The application provides a two-dimensional atomic layer material strain field control method, comprising the following steps: step 1, preparing a nano light absorption layer and a silicon dioxide nano film on a transparent substrate; step 2, transferring a two-dimensional atomic layer material to the surface of the silicon dioxide nano film; step 3, irradiating the nano light absorption layer with a focused laser beam through the transparent substrate, so as to obtain a silicon dioxide nano bump and apply a local strain to the two-dimensional atomic layer material; and step 4, applying a complex strain field to the two-dimensional atomic layer material by controlling the moving track and energy density of the focused laser beam, so as to complete the control of the strain field of the two-dimensional atomic layer material. The method provided by the embodiment of the application is simple, efficient and green, and has a wide application prospect in the strain regulation and control and device preparation of the two-dimensional atomic layer material.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of materials, and in particular to a two-dimensional atomic layer material strain field control method. BACKGROUND

[0002] For traditional semiconductor materials, strain engineering can weaken inter-valley scattering and improve transistor mobility. In recent years, strain engineering of two-dimensional atomic layer materials has also become an important research direction. Two most typical examples of strain regulation of two-dimensional atomic layer materials are listed as follows: (1) strain can induce graphene to generate a giant pseudo-magnetic field of up to 300 tesla or more, which has an important influence on the electronic properties, and in the absence of an external magnetic field, the quantum Hall effect and other physical properties can also be generated; (2) applying strain to two-dimensional atomic layer materials such as tungsten diselenide can prepare high-quality single-photon sources, which have great application potential in the integration of optical quantum devices. Among them, flexibly designing and controlling the strain field of two-dimensional atomic layer materials is the key and premise of strain regulation and device integration.

[0003] The following briefly introduces the current strain control technology for two-dimensional atomic layer materials. In 2017, Zhang Zhong et al. used a micrometer-sized bubble device to load biaxial tensile strain on double-layer graphene, and measured the interlayer shear force thereof, but this method needs to prepare a silicon oxide substrate with a specific size of micropore in advance. In 2018, M. Goldsche et al. prepared a micro-electro-mechanical device on an SOI substrate, and realized micro-scale stretching on a mechanically exfoliated graphene microparticle, but this method cannot control the strain distribution at present. In 2019, P. Jia et al. used an atomic force probe to apply a bias, induced to generate a graphene nanobubble with controllable position and shape, and observed a three-axis symmetric distribution pseudo-magnetic field on the parabolic bubble. In addition, transferring two-dimensional atomic layer materials such as graphene and tungsten diselenide to a substrate with nano-pillar, nano-pyramid and other structures can realize a specific strain distribution, but this method cannot realize continuous regulation and complex design of spatial strain gradient, and its strain regulation depends on a high-precision template, which is extremely high in cost and cannot be flexibly regulated.

[0004] The existing technology has the following problems and defects:

[0005] (1) The existing strain technology for two-dimensional atomic layer materials cannot realize complex strain field control, especially cannot realize the design and control of spatial strain gradient. A typical example in this regard is that manufacturing a graphene pseudo-magnetic field with uniform strength needs a three-fold symmetric distribution strain field, but the current technology cannot realize the control of the spatial strain gradient.

[0006] (2) The existing strain technology for two-dimensional atomic layer materials cannot realize flexible regulation of local large strain.

[0007] The difficulty of solving the above problems and defects is that the traditional strain loading technology is not applicable to two-dimensional atomic layer materials; there are a large number of atomic-scale interface strain transfer phenomena in the strain loading of two-dimensional atomic layer materials, and a large number of scientific problems have not been solved.

[0008] The significance of solving the above problems and defects is that a general strain field control method is established for hundreds of two-dimensional atomic layer materials, which can provide an accurate scientific research platform for the strain regulation of two-dimensional atomic layer materials in force, heat, light and electricity, and can also provide an integrated manufacturing method for large-scale strain devices. SUMMARY

[0009] The purpose of the present application is to solve the defects of the prior art, and to provide a two-dimensional atomic layer material strain field control method.

[0010] A two-dimensional atomic layer material strain field control method, comprising the following steps:

[0011] Step 1: preparing a nano light absorbing layer and a silicon dioxide nano film on a transparent substrate;

[0012] Step 2: transferring the two-dimensional atomic layer material to the surface of the silicon dioxide nano film;

[0013] Step 3: irradiating the nano light absorbing layer with a focused laser beam through the transparent substrate, thereby obtaining a silicon dioxide nano bump and applying a local strain to the two-dimensional atomic layer material;

[0014] Step 4: applying a complex strain field to the two-dimensional atomic layer material by controlling the moving track and energy density of the focused laser beam, thereby completing the control of the strain field of the two-dimensional atomic layer material.

[0015] Further, the two-dimensional atomic layer material strain field control method described above, the transparent substrate is a quartz substrate.

[0016] Further, the two-dimensional atomic layer material strain field control method described above, the nano light absorbing layer is a metal nano light absorbing layer or a non-metal nano light absorbing layer.

[0017] Further, the two-dimensional atomic layer material strain field control method described above, the metal nano light absorbing layer is a tin or indium metal nano light absorbing layer; the thickness is 5-30 nm.

[0018] Further, the two-dimensional atomic layer material strain field control method described above, the non-metal nano light absorbing layer is a polystyrene nano light absorbing layer; the thickness is 5-30 nm.

[0019] Further, the two-dimensional atomic layer material strain field control method as described above, the silicon dioxide nanometer film is an aluminum oxide or hafnium dioxide nanometer film, and the thickness is 10-100 nm.

[0020] Further, the two-dimensional atomic layer material strain field control method as described above, the two-dimensional atomic layer material includes graphene, molybdenum disulfide, and tungsten diselenide two-dimensional atomic layers, and the thickness is 1-10 atomic layers.

[0021] When the two-dimensional atomic layer material is a plurality of atomic layers, the angle between the upper and lower adjacent atomic layers is arbitrary, and the upper and lower adjacent atomic layers can be a heterostructure.

[0022] Further, the two-dimensional atomic layer material strain field control method as described above, the wavelength of the focused laser beam is selected according to specific applications in the ultraviolet to infrared band; the size of the focused spot is in the micron or sub-micron range; the incident angle of the focused laser beam is normal incidence; and the incident direction can be from the upper surface or from the lower surface.

[0023] Further, the two-dimensional atomic layer material strain field control method as described above, the movement track of the focused laser beam includes moving the substrate on which the two-dimensional atomic layer material is transferred or being controlled by a scanning galvanometer; the focused laser beam is a continuous laser or a pulsed laser; and the laser power is in the milliwatt range.

[0024] Further, the two-dimensional atomic layer material strain field control method as described above, the complex strain field includes uniform strain distribution, linearly varying strain distribution, quadratic curve strain distribution, and exponentially varying strain distribution.

[0025] Compared with the prior art, the present application can achieve complex strain field design and accurate control on various two-dimensional atomic layer materials by controlling the movement track and energy density of the focused laser beam, thereby achieving flexible regulation and control of super-large strain, and can be completed in one step of laser direct writing without any template, the whole process is simple and efficient, green and environmentally friendly, and has a wide application prospect.

[0026] The control method provided by the present application can be applied in the fields of two-dimensional atomic layer material pseudo-magnetic field control, two-dimensional atomic layer material band gap regulation and semiconductor device preparation, two-dimensional atomic layer material strain-induced quantum light source, and all two-dimensional atomic layer material strain engineering fields.

[0027] The local strain size of the two-dimensional atomic layer material according to the application can exceed 70%. Here, 70% refers to the strain loading capacity, and the higher the better. Large strain loading is conducive to achieving large-scale regulation of the material properties. For example, increasing the strain amount of graphene can increase its semiconductor band gap, which is the basis for using graphene to manufacture semiconductor optoelectronic devices. Here, the laser-induced nanodrum is used to load local tensile strain on graphene. The larger the aspect ratio of the nanodrum, the larger the strain amount that can be loaded. The formula for calculating the strain amount is ε m = f(v) · (h m / R) 2 , where h is the drum height, and R is the drum bottom radius.

[0028] The strain field of the two-dimensional atomic layer material according to the application can be flexibly controlled by laser energy and trajectory parameters, and does not require any template. That is, the application realizes complex strain field control, and only needs to use an ordinary laser direct writing system, a typical system including a computer-controlled laser (pulsed or continuous) and a moving platform (linear motor or piezoelectric ceramic drive). The laser can be used to mark points at a certain position, or can be used to mark points on any trajectory by means of the moving platform. By controlling the energy and spot size of a single laser pulse, the local strain field size and spatial distribution of the two-dimensional material can be controlled. If the laser beam is moved along a predetermined trajectory, the designed superposition of local strain can be further realized in the two-dimensional material, so that a more complex strain field can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a flow chart of a two-dimensional atomic layer material strain field control method based on laser-induced nanodrums provided by an embodiment of the application.

[0030] Figure 2 is a schematic diagram of an experiment of embodiment 1;

[0031] In the figure: 1, two-dimensional atomic layer material; 2, silicon dioxide nanofilm; 3, nanometer light absorption layer; 4, transparent substrate; 5, laser;

[0032] Figure 3 is an atomic force microscope characterization diagram of the experimental results of embodiment 1 of the application;

[0033] Figure 4 is an atomic force microscope characterization diagram of the experimental results of embodiment 2 of the application. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0035] As shown in the accompanying drawings, Figure 1 The present application provides a two-dimensional atomic layer material strain field control method, comprising the following steps:

[0036] Step 1: preparing a nano light-absorbing layer 3 and a silicon dioxide nano film 2 on a transparent substrate 4;

[0037] The transparent substrate 4 is a quartz substrate, and the nano light-absorbing layer 3 can be selected from metals or non-metals. The nano light-absorbing layer can be selected from low-melting-point metals such as tin and indium, and can be prepared by a magnetron sputtering or electron beam evaporation technology. The preferred thickness is 5-30 nm. The nano light-absorbing layer can also be selected from non-metal materials such as polystyrene, and can be prepared by a spin coating method. The preferred thickness is 5-30 nm.

[0038] The silicon dioxide nano film can also be replaced by transparent nano films such as aluminum oxide and hafnium dioxide. The silicon dioxide nano film can be prepared by a magnetron sputtering or electron beam evaporation technology. The preferred thickness is 10-100 nm.

[0039] Step 2: transferring a two-dimensional atomic layer material 1 to the surface of the silicon dioxide nano film 2;

[0040] The two-dimensional atomic layer material includes graphene, molybdenum disulfide, tungsten diselenide and various atomic layer materials. The thickness is 1-10 atomic layers. If it is a multi-layer atomic layer, the angle between the upper and lower adjacent atomic layers is arbitrary, and the upper and lower adjacent atomic layers can be a heterostructure (for example, the upper layer is graphene, and the lower layer is molybdenum disulfide).

[0041] Step 3: allowing a focused laser beam to irradiate the nano light-absorbing layer through the transparent substrate, so as to obtain a silicon dioxide nano bump and simultaneously apply a local strain to the two-dimensional atomic layer material;

[0042] The wavelength of the focused laser beam can be selected according to the absorption characteristics of different two-dimensional atomic layer materials to avoid damage to the material. The wavelength range is selected from the ultraviolet to infrared band. Since the detection and debugging of visible light are more convenient and safer, the present application preferably selects the visible band.

[0043] In order to improve the spatial accuracy of the strain field regulation, the optimal size of the focused laser beam of the present application is in the micron or sub-micron range.

[0044] In order to facilitate the control of the spatial distribution of the single-point local strain, and further control the spatial strain gradient, the laser incidence angle is preferably normal incidence.

[0045] The laser incidence direction can be flexibly selected, that is, the incidence direction can be incident from the upper surface where the two-dimensional atomic layer material is located, or incident from the lower surface where the transparent substrate is located, thereby facilitating the reduction of the complexity of the equipment and the device, simplifying the strain field regulation process, and improving the reliability of the strain field control.

[0046] The formation mechanism of the silicon dioxide nanobulge is that the intermediate nanometer light-absorbing layer is heated by laser, causing thermal expansion or phase change expansion, so that the surface layer silicon dioxide film of the nanometer light-absorbing layer is lifted to form a surface bulge (protrusion) structure. The lateral size of the silicon dioxide nanobulge is controlled by the laser spot diameter and the laser energy density; under a sub-micron spot, due to the mechanical self-limiting process of the multilayer film, the lateral size of the bulge can be less than 100 nm. The height of the silicon dioxide nanobulge can be mainly controlled by the laser energy density and can be adjusted in the range of 1 nm to 500 nm. Since the two-dimensional atomic layer material is attached to the surface of the silicon dioxide by van der Waals force, the formation of the silicon dioxide bulge can exert local tensile strain on the two-dimensional atomic layer material on the surface layer. The local strain size is mainly determined by the height of the bulge; the local strain distribution is mainly determined by the bulge morphology; and the spatial resolution of the local strain is mainly determined by the lateral size of the bulge.

[0047] The local strain size and spatial resolution of the two-dimensional atomic layer material can be precisely controlled by the morphology of the silicon dioxide bulge, and finally determined by the energy and spatial distribution of the focused laser spot.

[0048] The laser power of the focused laser beam in the application is in the order of milliwatt, which will not cause damage to the two-dimensional atomic layer material.

[0049] Step 4: A complex strain field is exerted on the two-dimensional atomic layer material by controlling the moving track and energy density of the focused laser beam, so as to complete the control of the strain field of the two-dimensional atomic layer material.

[0050] The track of the focused laser beam is controlled by a two-dimensional nanometer moving stage or a scanning galvanometer. The laser can be continuous output or pulsed output; preferably pulsed output, so as to realize more abundant strain field control. The complex strain field mainly refers to the complex change of the spatial strain gradient, such as realizing uniform strain distribution, linear change type strain distribution, quadratic curve type strain distribution, exponential change type strain distribution and other common spatial strain gradients.

[0051] Embodiment:

[0052] The graphite crystal used in the embodiment of the application is purchased from Pioneer Nanometer Company.

[0053] The electron beam evaporation system in the embodiment of the application is Torr International, Inc.

[0054] The laser power data in the application is measured by a high-precision laser power meter (model THORLABS PM100A) of nanowatt level.

[0055] The brand and model of the 488nm used in the embodiment of the application are Coherent Sapphire.

[0056] The brand and model of the nanometer mobile station used in the embodiment of the application are Physik Instrumente P-563.3CD.

[0057] The technical solutions of the application are further described below in combination with specific embodiments.

[0058] Embodiment 1:

[0059] This embodiment shows the construction of a grid-type complex strain field in a graphene two-dimensional atomic layer material (few-layer graphene, a few graphene atomic layers), and the specific process includes:

[0060] (1) As shown in FIG. 1, a 5nm-thick metal tin light-absorbing layer and a 30nm-thick silicon dioxide layer are prepared in sequence on a clean quartz substrate by using an electron beam evaporation system. Figure 2

[0061] (2) Few-layer graphene is peeled off from a graphite crystal by using a mechanical peeling method, and transferred to the surface of the silicon dioxide layer, as shown in FIG. 2. Figure 2

[0062] (3) As shown in FIG. 3, a focused laser beam is incident from one side of the quartz substrate to the metal tin light-absorbing layer, and a local strain field is constructed in the few-layer graphene. Figure 2

[0063] (4) The movement of the graphene sample (equivalent to the movement of the laser beam) is controlled by using a nanometer mobile station, a grid-type complex strain field is constructed in the graphene, and the complex strain field distribution can be characterized by using an atomic force microscope, and the characterization result is shown in FIG. 4. Figure 3

[0064] Embodiment 2:

[0065] This embodiment shows the construction of a sinusoidal continuous variation strain field in silicon dioxide, and the specific process includes:

[0066] (1) A 5nm-thick metal tin light-absorbing layer and a 30nm-thick silicon dioxide layer are prepared in sequence on a clean quartz substrate by using an electron beam evaporation system.

[0067] ​​​​(2) Using a focused laser beam to irradiate the metal tin light-absorbing layer from the quartz side, and constructing a local strain field in the silicon dioxide layer.

[0068] (3) Using a nano-moving stage to control the sample movement (equivalent to laser beam movement), constructing a sinusoidal continuous variation strain field in the silicon dioxide layer, and using an atomic force microscope to characterize the complex strain field distribution, and the characterization results are as shown in Figure 4

[0069] As can be seen from the embodiments 1 and 2, the method based on laser-induced nano-bulge can be used to construct a complex strain field in a two-dimensional atomic layer material such as graphene, to realize the design and control of a complex spatial strain gradient, and the local strain can be flexibly adjusted, and can be completed by one-step laser direct writing.

[0070] The method provided by the embodiments of the present application is simple and efficient, green and environmentally friendly, and has a broad application prospect in the strain regulation and device preparation of two-dimensional atomic layer materials.

[0071] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.​

Claims

1. A method for controlling the strain field of a two-dimensional atomic layer material, characterized in that, Includes the following steps: Step 1: Prepare a light-absorbing nanolayer and a silica nanofilm on a transparent substrate; the silica nanofilm is an aluminum oxide or hafnium dioxide nanofilm; Step 2: Transfer the two-dimensional atomic layer material onto the surface of the silica nanofilm; Step 3: A focused laser beam is passed through the transparent substrate and irradiates the nano-absorbing layer. The laser beam heats the intermediate nano-absorbing layer, causing thermal expansion or phase transition expansion, which pushes up the silica film on the surface of the nano-absorbing layer, forming a surface bulge. The lateral size of the bulge is controlled by the laser spot diameter and laser energy density. At the same time, local strain is applied to the two-dimensional atomic layer material. The magnitude of the local strain is determined by the height of the bulge. The distribution of the local strain is determined by the morphology of the bulge. The spatial resolution of the local strain is determined by the lateral size of the bulge. Step 4: By controlling the movement trajectory and energy density of the focused laser beam, a complex strain field is applied to the two-dimensional atomic layer material, thereby completing the control of the strain field of the two-dimensional atomic layer material; When a two-dimensional atomic layer material consists of multiple atomic layers, the angle between adjacent atomic layers is arbitrary, and the adjacent atomic layers are heterogeneous structures.

2. The strain field control method for two-dimensional atomic layer materials according to claim 1, characterized in that, The transparent substrate is a quartz substrate.

3. The strain field control method for two-dimensional atomic layer materials according to claim 1, characterized in that, The nano-absorbing layer can be a metallic nano-absorbing layer or a non-metallic nano-absorbing layer.

4. The strain field control method for two-dimensional atomic layer materials according to claim 3, characterized in that, The metal nano-absorbing layer is a tin or indium metal nano-absorbing layer with a thickness of 5–30 nm.

5. The strain field control method for two-dimensional atomic layer materials according to claim 3, characterized in that, The non-metallic nano-absorbing layer is a polystyrene nano-absorbing layer with a thickness of 5–30 nm.

6. The strain field control method for two-dimensional atomic layer materials according to claim 1, characterized in that, The two-dimensional atomic layer material includes graphene, molybdenum disulfide, and tungsten diselenide two-dimensional atomic layers with a thickness of 1 to 10 atoms.

7. The strain field control method for two-dimensional atomic layer materials according to claim 1, characterized in that, The wavelength of the focused laser beam is selected in the ultraviolet to infrared band; the size of the focused spot is in the micrometer or submicrometer range; the incident angle of the focused laser beam is normal incidence; and the incident direction is either from the upper surface or from the lower surface.

8. The strain field control method for two-dimensional atomic layer materials according to claim 1, characterized in that, The substrate with two-dimensional atomic layer material is moved or the trajectory of the focused laser beam is controlled by a scanning galvanometer; the focused laser beam is a continuous laser or a pulsed laser; the laser power is on the order of milliwatts.

9. The strain field control method for two-dimensional atomic layer materials according to claim 1, characterized in that, The complex strain field includes: uniform strain distribution, linear strain distribution, quadratic strain distribution, and exponential strain distribution.

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