WO2024026785A1

WO2024026785A1 - Two-dimensional nanosheet and preparation method therefor

Info

Publication number: WO2024026785A1
Application number: PCT/CN2022/110357
Authority: WO
Inventors: 耿凤霞; 嵇锦鹏; 蒋坤
Original assignee: 苏州大学
Priority date: 2022-08-04
Filing date: 2022-08-04
Publication date: 2024-02-08

Abstract

A preparation method for a two-dimensional nanosheet. The method comprises: performing a calendering treatment on non-Van der Waals layered crystal particles, and then performing mechanical exfoliation, so as to obtain a two-dimensional nanosheet. Mechanical exfoliation is commonly referred to as a scotch tape method, and mechanical exfoliation may only be performed by using an adhesive tape (sometimes, the assistance of an interposer is required) when the interlayer interaction of a bulk material is dominated by a weak van der Waals force; however, there is significant electron density overlapping between layers of many functional materials with layered stacked crystal structures, and the electron density overlapping forms a non-Van der Waals structure, which cannot be directly exfoliated by using the adhesive tape. In the present method, few-layer or even single-layer structures of various non-Van der Waals layered crystal materials are successfully obtained for the first time by means of a calendering pretreatment combined with mechanical exfoliation; in addition, a new physical phenomenon can be observed in an exfoliated two-dimensional crystal.

Description

一种二维纳米片及其制备方法Two-dimensional nanosheet and preparation method thereof

技术领域Technical field

本发明属于纳米技术，具体涉及一种二维纳米片及其制备方法。The invention belongs to nanotechnology, and specifically relates to a two-dimensional nanosheet and a preparation method thereof.

背景技术Background technique

二维材料具有几个原子层甚至单原子层的厚度，近年来引起了人们极大的兴趣。将厚度限制在亚纳米级将赋予该材料大量与维度相关的新异物理特性和应用（Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric Field Effect in Atomically Thin Carbon Films. Science 2004, 306, 666−669. Tan, C.; Cao, X.; Wu, X.; He, Q.; Yang, J.; Zhang, X.; Chen, J.; Zhao, W.; Han, S.; Nam, G.-H.; Sindoro, M.; Zhang, H. Recent Advances in Ultrathin Two-Dimensional Nanomaterials. Chem. Rev. 2017, 117, 6225−6331.Butler, S. Z.; Hollen, S. M.; Cao, L.; Cui, Y.; Gupta, J. A.; Gutierrez, H. R.; Heinz, T. F.; Hong, S. S.; Huang, J.; Ismach, A. F.; Johnston-Halperin, E.; Kuno, m.; Plashnitsa, V. V.; Robinson, R. D.; Ruoff, R. S.; Salahuddin, S.; Shan, J.; Shi, L.; Spencer, M. G.; Terrones, M.; et al. Progress, Challenges, and Opportunities in Two Dimensional Materials beyond Graphene. ACS Nano 2013, 7, 2898−2926.Zhou, J.; Lin, J.; Huang, X.; Zhou, Y.; Chen, Y.; Xia, J.; Wang, H.; Xie, Y.; Yu, H.; Lei, J.; Wu, D.; Liu, F.; Fu, Q.; Zeng, Q.; Hsu, C.-H.; Yang, C.; Lu, L.; Yu, T.; Shen, Z.; Lin, H.; Yakobson, B.; Liu, Q.; Suenaga, K.; Liu, G.; Liu, Z. A Library of Atomically Thin Metal Chalcogenides. Nature 2018, 556, 355−361.）。机械剥离，通常又被称为透明胶带法，因为过程中不涉及化学反应，被认为是获得高质量二维材料，并保留其本征结构和特性的最佳方法。引入辅助中介层（例如，Au、Al ₂O ₃等）可用于增强基板与目标晶体的粘附性并增加接触面积，从而剥离大尺寸纳米薄片。但是该方法针对不同剥离对象需要选择不同中介材料，尤其是剥离后还需要通过复杂的方法去除中介材料，且引入的杂质会极大限制二维材料的本征性质。此外，只有当块体材料中的层间相互作用由弱范德华（vdW）力主导时，才可能使用胶带（有时在中介层的协助下）进行机械剥离（Deng, Y.; Yu, Y.; Song, Y.; Zhang, J.; Wang, N.; Sun, Z.; Yi, Y.; Wu, Y.; Wu, S.; Zhu, J.; Wang, J.; Chen X.; Zhang, Y. Gate-Tunable Room-Temperature Ferromagnetism in Two-Dimensional Fe ₃GeTe ₂. Nature 2018, 563, 94−99）。在首次成功机械剥离石墨烯后，六方氮化硼（h-BN）、过渡金属二卤化物（TMD）、金属有机骨架（MOF）、黑磷（BP）等层状材料的单层结构也相继被报道。值得注意的是，有许多功能材料具有层状堆垛晶体结构，但层与层之间存在显著的电子密度重叠。例如，一些金属氧化物可以被视为刚性层的堆叠，其中每层由通过边缘或角连接并以二维方式延伸的金属-氧多面体组成。这些结构中的相邻层之间通常具有金属或静电吸引力，称为非范德华结构（non-vdW），其层间相互作用明显高于范德华层状结构。由于相邻层之间存在强烈的电子耦合，无法将这些材料直接机械剥离成单层或少层。从结构-性能关系和新二维类似物的潜在应用角度来看，这类非范德华材料的机械剥离薄层是有趣和重要的。因此，开发一种机械剥离非范德华层状结构的方法是非常必要的。 Two-dimensional materials, which are several atomic layers or even single atomic layers thick, have attracted great interest in recent years. Limiting the thickness to the subnanometer scale will endow the material with a host of novel dimensionally relevant physical properties and applications (Novoselov, KS; Geim, AK; Morozov, SV; Jiang, D.; Zhang, Y.; Dubonos, SV; Grigorieva , IV; Firsov, AA Electric Field Effect in Atomically Thin Carbon Films. Science 2004 , 306 , 666−669. Tan, C.; Cao, X.; Wu, X.; He, Q.; Yang, J.; Zhang , X.; Chen, J.; Zhao, W.; Han, S.; Nam, G.-H.; Sindoro, M.; Zhang, H. Recent Advances in Ultrathin Two-Dimensional Nanomaterials. Chem. Rev. 2017 , 117 , 6225−6331.Butler, SZ; Hollen, SM; Cao, L.; Cui, Y.; Gupta, JA; Gutierrez, HR; Heinz, TF; Hong, SS; Huang, J.; Ismach, AF; Johnston-Halperin, E.; Kuno, m.; Plashnitsa, VV; Robinson, RD; Ruoff, RS; Salahuddin, S.; Shan, J.; Shi, L.; Spencer, MG; Terrones, M.; et al . Progress, Challenges, and Opportunities in Two Dimensional Materials beyond Graphene. ACS Nano 2013 , 7 , 2898−2926. Zhou, J.; Lin, J.; Huang, X.; Zhou, Y.; Chen, Y.; Xia , J.; Wang, H.; Xie, Y.; Yu, H.; Lei, J.; Wu, D.; Liu, F.; Fu, Q.; Zeng, Q.; Hsu, C.-H .; Yang, C.; Lu, L.; Yu, T.; Shen, Z.; Lin, H.; Yakobson, B.; Liu, Q.; Suenaga, K.; Liu, G.; Liu, Z . A Library of Atomically Thin Metal Chalcogenides. Nature 2018 , 556 , 355−361.). Mechanical peeling, often called the Scotch tape method because no chemical reaction is involved in the process, is considered the best method to obtain high-quality 2D materials while retaining their intrinsic structure and properties. The introduction of auxiliary interposers (e.g., Au, Al ₂ O _3, etc.) can be used to enhance the adhesion between the substrate and the target crystal and increase the contact area, thereby exfoliating large-sized nanoflakes. However, this method requires the selection of different intermediary materials for different stripping objects. In particular, complex methods need to be used to remove the intermediary materials after stripping, and the introduced impurities will greatly limit the intrinsic properties of the two-dimensional material. Furthermore, mechanical exfoliation using tape (sometimes with the assistance of an interposer) is only possible when the interlayer interactions in the bulk material are dominated by weak van der Waals (vdW) forces (Deng, Y.; Yu, Y.; Song, Y.; Zhang, J.; Wang, N.; Sun, Z.; Yi, Y.; Wu, Y.; Wu, S.; Zhu, J.; Wang, J.; Chen X.; Zhang , Y. Gate-Tunable Room-Temperature Ferromagnetism in Two-Dimensional Fe ₃ GeTe ₂ . Nature 2018 , 563 , 94−99). After the first successful mechanical exfoliation of graphene, single-layer structures of layered materials such as hexagonal boron nitride (h-BN), transition metal dichalcogenide (TMD), metal organic framework (MOF), black phosphorus (BP), etc. also followed. was reported. It is worth noting that there are many functional materials with layered stacking crystal structures, but with significant electron density overlap between layers. For example, some metal oxides can be viewed as stacks of rigid layers, where each layer consists of metal-oxygen polyhedra connected by edges or corners and extending in two dimensions. There are usually metallic or electrostatic attractions between adjacent layers in these structures, called non-van der Waals structures (non-vdW), and their interlayer interactions are significantly higher than those in van der Waals layered structures. These materials cannot be directly mechanically exfoliated into single or few layers due to the strong electronic coupling between adjacent layers. The mechanical exfoliation of thin layers of this class of non-van der Waals materials is interesting and important from the perspective of structure-property relationships and potential applications of new 2D analogs. Therefore, it is highly necessary to develop a method to mechanically exfoliate non-van der Waals layered structures.

技术问题technical problem

本发明的方法包括一种简单的压延预处理，然后使用透明胶带进行机械剥离以获得薄层；成功剥离多种材料，包括金属（Bi、Sb）、半导体金属氧化物和硫族化合物（SnO、V ₂O ₅、Bi ₂O ₂Se）以及超导化合物（KV ₃Sb ₅）。电子密度理论计算验证了这些结构层间存在强电子耦合，且剥离能通常比石墨的剥离能高出几倍，这自然会使这些材料的常规剥落变得困难，甚至不可行。 The method of the present invention includes a simple calendering pretreatment, followed by mechanical peeling using transparent tape to obtain thin layers; successfully peeling off a variety of materials, including metals (Bi, Sb), semiconductor metal oxides and chalcogenides (SnO, V ₂ O ₅ , Bi ₂ O ₂ Se) and superconducting compounds (KV ₃ Sb ₅ ). Electron density theoretical calculations have verified the existence of strong electronic coupling between the layers of these structures, and the exfoliation energy is usually several times higher than that of graphite, which naturally makes routine exfoliation of these materials difficult or even unfeasible.

技术解决方案Technical solutions

本发明采用如下技术方案：一种二维纳米片的制备方法，将晶体颗粒压延处理，然后机械剥离，得到二维纳米片；优选的，将晶体颗粒平铺后进行压延处理，然后通过机械剥离，得到二维纳米片。The present invention adopts the following technical solution: a method for preparing two-dimensional nanosheets. The crystal particles are rolled and then mechanically peeled off to obtain two-dimensional nanosheets. Preferably, the crystal particles are flattened and then rolled and then mechanically peeled off. , obtaining two-dimensional nanosheets.

本发明中，晶体颗粒为非范德华层状结构晶体颗粒，比如金属颗粒、半导体金属氧化物颗粒、硫族化合物颗粒、超导化合物颗粒等，作为示例，晶体颗粒为金属（Bi、Sb）、半导体金属氧化物和硫族化合物（SnO、V ₂O ₅、Bi ₂O ₂Se）以及超导化合物（KV ₃Sb ₅）晶体颗粒；优选的，晶体颗粒的粒径为微米级至毫米级，比如1μm～5mm，优选1～500μm，进一步的，为10～200μm。 In the present invention, the crystal particles are non-van der Waals layered structure crystal particles, such as metal particles, semiconductor metal oxide particles, chalcogenide particles, superconducting compound particles, etc. As an example, the crystal particles are metal (Bi, Sb), semiconductor Metal oxides and chalcogen compounds (SnO, V ₂ O ₅ , Bi ₂ O ₂ Se) and superconducting compounds (KV ₃ Sb ₅ ) crystal particles; preferably, the particle size of the crystal particles is from micron to millimeter, such as 1 μm to 5 mm, preferably 1 to 500 μm, and further, 10 to 200 μm.

本发明中，采用滚轮或者棒进行压延处理，优选的，压延荷重为0.5～10Kg，速度为10～300mm/min。对于范德华结构的晶体，比如石墨，可通过常规的机械剥离得到二维纳米片，但是对于具有层间强相互作用的非范德华结构晶体颗粒，无法通过常规的机械剥离得到二维纳米片，本发明创造性的提出压延后进行常规的机械剥离，得到二维纳米片，厚度在0.1nm～50nm，尤其在0.1nm～30nm，特别是0.3nm～10nm，更重要的是0.5 nm～5nm。In the present invention, rollers or rods are used for rolling processing. Preferably, the rolling load is 0.5-10Kg and the speed is 10-300mm/min. For crystals with a van der Waals structure, such as graphite, two-dimensional nanosheets can be obtained through conventional mechanical exfoliation. However, for crystal particles with a non-van der Waals structure with strong interlayer interactions, two-dimensional nanosheets cannot be obtained through conventional mechanical exfoliation. The present invention It is creatively proposed to perform conventional mechanical peeling after rolling to obtain two-dimensional nanosheets with a thickness of 0.1nm~50nm, especially 0.1nm~30nm, especially 0.3nm~10nm, and more importantly, 0.5nm~5nm.

本发明中，机械剥离为胶带剥离，采用胶带粘住颗粒对折按压然后撕开，薄层材料会粘在胶带上，此方法具体操作为常规技术，现有技术利用此进行石墨剥离得到石墨烯，但是直接采用胶带剥离无法使得非范德华层状结构晶体减薄或者得到纳米级薄片，更不会得到单层或者少层二维纳米片。In the present invention, mechanical peeling is tape peeling. The tape is used to stick the particles by folding, pressing and then tearing apart. The thin layer of material will stick to the tape. The specific operation of this method is conventional technology. The existing technology uses this to peel off graphite to obtain graphene. However, direct tape peeling cannot thin non-van der Waals layered crystals or obtain nanoscale flakes, let alone single-layer or few-layer two-dimensional nanosheets.

本发明中，压延为单向压延，此为常规理解，比如滚轮压着晶体颗粒的行进方向为单向，不是来回压着晶体颗粒行进。In the present invention, rolling is unidirectional rolling, which is a conventional understanding. For example, the roller presses the crystal particles in one direction and does not press the crystal particles back and forth.

作为示例，将晶体颗粒平铺在电动压延滚轮设备的底板上，然后单向单轮压延，得到压延颗粒；再使用透明胶带粘压延颗粒，然后剥离，得到薄层，即本发明的产品二维纳米片，可制备二维纳米片组装体材料，比如超导材料、光学材料、电极材料、导热材料、导电材料等。As an example, the crystal particles are laid flat on the bottom plate of the electric calendering roller equipment, and then calendered in one direction and in one wheel to obtain the calendered particles; then a transparent tape is used to stick the calendered particles, and then peeled off to obtain a thin layer, that is, the two-dimensional product of the present invention Nanosheets can prepare two-dimensional nanosheet assembly materials, such as superconducting materials, optical materials, electrode materials, thermally conductive materials, conductive materials, etc.

有益效果beneficial effects

本发明使用压延预处理，然后进行透明胶带剥离，首次成功地获得了几种材料的少层甚至单层结构，并且能够在剥离的二维材料中观察到令人兴奋的新现象。金属锑变成了带隙为2.01 eV的半导体；半导体SnO的光吸收范围能够从红外区（IR）调控到紫外区，带隙从块体的0.60 eV调控为单层的3.65 eV。此外，KV ₃Sb ₅薄片是一种非常有前景的二维超导材料。因此，本发明的新结果为非范德华层状材料的机械解理提出了一个通用方法，并提供了多种新的2D材料。 The present invention uses calendering pretreatment followed by transparent tape peeling to successfully obtain few-layer or even single-layer structures of several materials for the first time, and is able to observe exciting new phenomena in the peeled two-dimensional materials. Metal antimony becomes a semiconductor with a band gap of 2.01 eV; the light absorption range of the semiconductor SnO can be adjusted from the infrared region (IR) to the ultraviolet region, and the band gap is adjusted from 0.60 eV in the bulk to 3.65 eV in the single layer. In addition, KV ₃ Sb ₅ flakes are a very promising two-dimensional superconducting material. Therefore, the new results of the present invention propose a general method for the mechanical cleavage of non-van der Waals layered materials and provide a variety of new 2D materials.

附图说明Description of drawings

图1（a）为对于本发明中研究的非范德华层状材料的剥离能（meVÅ ^-2）；还列出了石墨的值，以供参考。非范德华层状结构的剥离能通常是石墨（其在vdW力范围内）的1.3-3.6倍。根据参考文献（Nano Lett. 2018, 182759-2765），剥离能计算为块体材料（每个原子层）和单个偏差层之间基态能量的差值。（b）为计算出的本发明材料代表性结构的电荷密度差等高线图，显示出强烈的层间耦合；红色和蓝色等值面分别代表电子积累和耗尽。（c）为相应的AFM图像，显示了这些材料为单层或少层。 Figure 1(a) shows the exfoliation energy (meV Å ^-2 ) for the non-van der Waals layered materials studied in this invention; the values for graphite are also listed for reference. The exfoliation energy of non-van der Waals layered structures is typically 1.3-3.6 times that of graphite (which is in the vdW force range). According to the reference (Nano Lett. 2018, 182759-2765), the exfoliation energy is calculated as the difference in ground state energy between the bulk material (each atomic layer) and the individual deviation layers. (b) is a calculated contour diagram of the charge density difference of a representative structure of the material of the present invention, showing strong interlayer coupling; the red and blue isosurfaces represent electron accumulation and depletion respectively. (c) is the corresponding AFM image, showing these materials as single or few layers.

图2为剥离单层SnO的理论稳定性预测。（a）SnO的侧视图和俯视图。（b）SnO晶体结构的电荷密度差的计算等值线图，显示层间电子密度降低和层间相互作用衰减；红色和蓝色区域分别代表电子积累和耗尽。（c）单层SnO的谐波声子色散谱。（d）温度（左上角）和总能量（左下角）随轨迹时间的变化，从300和600 K下单层SnO的分子动力学模拟中获得；右图：分子动力学模拟结束时的相应快照。（e）使用密度泛函计算的爬坡弹性带（CI-NEB）方法计算了SnO层上O ₂离解的最小能量路径。插图：沿路径具有代表性的CI-NEB构型，包括分子氧稳定吸附的初始状态、过渡状态和游离原子氧的最终状态。计算出的O ₂解离势垒为0.58 eV，表明SnO薄片在正常条件下对O ₂攻击具有良好的稳定性。 Figure 2 shows the theoretical stability prediction of exfoliated monolayer SnO. (a) Side view and top view of SnO. (b) Calculated contour plot of the charge density difference of the SnO crystal structure, showing the decrease in interlayer electron density and the decay of interlayer interactions; the red and blue areas represent electron accumulation and depletion, respectively. (c) Harmonic phonon dispersion spectrum of a single layer of SnO. (d) Temperature (top left) and total energy (bottom left) as a function of trajectory time, obtained from molecular dynamics simulations of a single layer of SnO at 300 and 600 K; right: corresponding snapshots at the end of the molecular dynamics simulation. . (e) The _minimum energy path for O dissociation on the SnO layer is calculated using the climbing elastic band (CI-NEB) method of density functional calculations. Inset: Representative CI-NEB configurations along the path, including the initial state of stable adsorption of molecular oxygen, the transition state, and the final state of free atomic oxygen. The calculated O _dissociation barrier is 0.58 eV, indicating that SnO flakes have good stability against _O attack under normal conditions.

图3为压延前后晶体结构的表征。（a）SnO晶体的XRD图谱和（b）拉曼光谱。压延处理后的SnO晶体表示为M-SnO。SnO晶体（c）在压延处理之前和（d）在压延处理之后的SEM图像。每个图中的插图显示了堆叠平面的示意图。（e）通过AFM测量SnO上的侧向力。插图：实验示意图。（f） SnO和M-SnO晶体的横截面STEM图像。Figure 3 shows the characterization of the crystal structure before and after rolling. (a) XRD pattern and (b) Raman spectrum of SnO crystal. The rolled SnO crystal is represented as M-SnO. SEM images of SnO crystals (c) before rolling treatment and (d) after rolling treatment. The inset in each figure shows a schematic representation of the stacked plane. (e) Measurement of lateral force on SnO by AFM. Inset: Schematic of the experiment. (f) Cross-sectional STEM images of SnO and M-SnO crystals.

图4为不同厚度SnO薄片的特征。（a）玻璃基板上剥离的SnO层的典型光学显微镜图像。（b-f）厚度为1-5层的SnO薄片的代表性AFM图像。（g） SnO薄片的高分辨率TEM图像。（h）将单层SnO的拉曼光谱与块体SnO进行比较，并与暴露于空气中3个月并在空气中额外加热至200℃后的拉曼光谱进行比较；激光波长：532 nm。Figure 4 shows the characteristics of SnO flakes with different thicknesses. (a) Typical optical microscope image of an exfoliated SnO layer on a glass substrate. (b–f) Representative AFM images of SnO flakes with a thickness of 1–5 layers. (g) High-resolution TEM image of SnO flakes. (h) Comparison of the Raman spectrum of a single layer of SnO to that of bulk SnO and to that after exposure to air for 3 months and additional heating to 200°C in air; laser wavelength: 532 nm.

图5为（a）SnO薄片的拉曼光谱；插图：纳米片的光学图像。（b）A _1g和（c）E _g是在15×15μm ²面积上收集的拉曼强度mapping图，步长为500 nm。结果表明，厚度均匀性高，局部键合结构良好。 Figure 5 shows (a) Raman spectrum of SnO flakes; inset: optical image of nanosheets. (b) A _1g and (c) E _g are Raman intensity mapping images collected on ^an area of 15 × 15 μm with a step size of 500 nm. The results show high thickness uniformity and good local bonding structure.

图6为Si/SiO ₂衬底上SnO片在暴露于环境空气中3个月前后以及在200℃空气中额外加热后的AFM图像。 Figure 6 shows AFM images of SnO flakes on Si/SiO _substrate before and after exposure to ambient air for 3 months and after additional heating in air at 200°C.

图7为单层SnO薄片与SnO块体的物理性能比较。（a）能带结构，（b）通过绘制（Ahv） ^1/2与hv的关系来实验估计带隙，实验值和拟合值分别以实线和虚线绘制。带隙调控覆盖了从红外到紫外的整个光谱范围。（c）锑的能带结构和（d）带隙的实验估计。当减薄到单层时，金属块体材料转化为带隙为2.01 eV的半导体。（e）从块体到单层SnO和Sb的带隙调控范围与其他已报道二维半导体的比较。 Figure 7 shows a comparison of the physical properties of single-layer SnO flakes and SnO bulk. (a) Energy band structure, (b) Experimental estimation of the band gap by plotting (Ahv) ^1/2 versus hv, with experimental and fitted values plotted as solid and dashed lines, respectively. Bandgap regulation covers the entire spectral range from infrared to ultraviolet. (c) Energy band structure of antimony and (d) experimental estimation of the band gap. When thinned to a single layer, the bulk metal material transforms into a semiconductor with a band gap of 2.01 eV. (e) Comparison of the band gap control range from bulk to single-layer SnO and Sb with other reported two-dimensional semiconductors.

图8为（a）通过紫外-可见（UV-Vis）吸收分析SnO纳米片的光学透过率和（b）吸光度。使用紫外-可见光谱仪在透明石英板基板上沉积的单个薄片上收集光谱，激光光斑半径为2μm；插图（a）：单个薄片和大块SnO晶体的光学照片。箭头表示厚度增加。（c）带隙随厚度的变化图。Figure 8 shows (a) optical transmittance and (b) absorbance of SnO nanosheets analyzed by ultraviolet-visible (UV-Vis) absorption. Spectra were collected using a UV-visible spectrometer on individual flakes deposited on a transparent quartz plate substrate with a laser spot radius of 2 μm; inset (a): optical photographs of individual flakes and bulk SnO crystals. Arrows indicate increased thickness. (c) Band gap as a function of thickness.

图9为Bi材料的特性。（a-b）代表性SEM图像和（c）X射线衍射图谱。铋粉购自阿拉丁实业有限公司。微晶的横向尺寸约为50μm。Figure 9 shows the characteristics of Bi material. (a-b) Representative SEM images and (c) X-ray diffraction patterns. Bismuth powder was purchased from Aladdin Industrial Co., Ltd. The lateral size of the crystallites is approximately 50 μm.

图10为Sb材料的特性。（a-b）代表性SEM图像和（c）X射线衍射图谱。Sb粉末购自阿拉丁实业有限公司。微晶的横向尺寸约为60-80μm。Figure 10 shows the characteristics of Sb material. (a-b) Representative SEM images and (c) X-ray diffraction patterns. Sb powder was purchased from Aladdin Industrial Co., Ltd. The lateral size of the crystallites is approximately 60-80 μm.

图11为V ₂O ₅材料的特性。（a-b）不同放大倍数的代表性SEM图像和（c）X射线衍射图谱。五氧化二钒粉末购自阿拉丁实业有限公司。微晶的横向尺寸约为150的μm。 Figure 11 shows the characteristics of V ₂ O ₅ material. (ab) Representative SEM images at different magnifications and (c) X-ray diffraction patterns. Vanadium pentoxide powder was purchased from Aladdin Industrial Co., Ltd. The lateral size of the crystallites is approximately 150 μm.

图12为Bi ₂O ₂Se材料的表征。（a-b）不同放大倍数的代表性SEM图像和（c） X射线衍射图谱。Bi ₂O ₂Se粉末购自阿拉丁实业有限公司。微晶的横向尺寸约为50μm。 Figure 12 shows the characterization of Bi ₂ O ₂ Se material. (ab) Representative SEM images at different magnifications and (c) X-ray diffraction patterns. Bi ₂ O ₂ Se powder was purchased from Aladdin Industrial Co., Ltd. The lateral size of the crystallites is approximately 50 μm.

图13为单晶KV ₃Sb ₅材料的特性。（a-b）不同放大倍数的代表性SEM图像。（c） X射线衍射图谱。 Figure 13 shows the characteristics of single crystal KV ₃ Sb ₅ material. (ab) Representative SEM images at different magnifications. (c) X-ray diffraction pattern.

图14为（a）Si/SiO ₂衬底上Sb纳米片的AFM图像；从左到右：刚剥离的薄片，暴露在空气中3个月后的薄片，以及在200℃空气中额外加热10分钟后的薄片，以及（b）相应的拉曼光谱。在薄片形态、厚度或光谱特征方面未观察到明显变化，表明其具有良好的抗O ₂稳定性。 Figure 14 is (a) AFM image of Sb nanosheets on Si/SiO _substrate ; from left to right: freshly peeled flakes, flakes after 3 months of exposure to air, and additional heating in air at 200°C for 10 Minutes later, and (b) the corresponding Raman spectrum. No obvious changes were observed in flake morphology, thickness or spectral characteristics, indicating good stability against _O2 .

图15为（a）Si/SiO ₂衬底上Bi纳米片的AFM图像；从左到右：刚剥离的薄片，暴露在空气中3个月后的薄片，以及在150℃和200℃的空气中额外加热10分钟后的薄片，以及（b）相应的拉曼光谱。在高达150℃的温度下，未观察到纳米片形态、厚度或光谱特征的明显变化，表明Bi纳米片具有良好的抗O ₂稳定性。 Figure 15 shows (a) AFM images of Bi nanosheets on Si/SiO _substrate ; from left to right: freshly peeled flakes, flakes after exposure to air for 3 months, and air at 150°C and 200°C The flake after additional heating for 10 minutes, and (b) the corresponding Raman spectrum. No obvious changes in nanosheet morphology, thickness or spectral characteristics were observed at temperatures up to 150°C, indicating that Bi nanosheets have good stability against _O2 .

图16为（a）Si/SiO ₂衬底上Bi ₂O ₂Se片的AFM图像；从左到右：刚剥落的薄片，暴露在空气中3个月后的薄片，以及在200℃空气中加热10分钟后的薄片，以及（b）相应的拉曼光谱。未观察到薄片形态、厚度或光谱特征的明显变化，表明Bi纳米片具有良好的抗O ₂稳定性。 Figure 16 shows (a) AFM images of Bi ₂ O ₂ Se flakes on Si/SiO ₂ substrate; from left to right: freshly peeled flakes, flakes after exposure to air for 3 months, and in air at 200°C The flake after heating for 10 minutes, and (b) the corresponding Raman spectrum. No obvious changes in flake morphology, thickness or spectral characteristics were observed, indicating that the Bi nanosheets have good stability against _O2 .

图17为厚度小于2 nm（一层或两层）的KV ₃Sb ₅的代表性AFM图像。 Figure 17 is a representative AFM image of KV ₃ Sb ₅ with a thickness less than 2 nm (one or two layers).

图18为的载玻片基板上直接胶带剥离的SnO片的光学显微代表性图像（在透射模式下采集），可看出这些分层晶体仍然很厚且不透明。Figure 18 is a representative optical microscopy image (acquired in transmission mode) of directly tape-stripped SnO flakes on a glass slide substrate. It can be seen that these layered crystals are still thick and opaque.

本发明的实施方式Embodiments of the invention

非范德华层状结构的剥离能通常比石墨的高出几倍（图1a），这自然会使这些材料的剥落变得困难。本发明的方法包括一种简单的压延预处理，然后使用透明胶带进行机械剥离以获得薄层，成功剥离多种材料，包括金属（Bi、Sb）、半导体金属氧化物和硫族化合物（SnO、V ₂O ₅、Bi ₂O ₂Se）以及超导化合物（KV ₃Sb ₅），电子密度计算验证了这些结构层之间存在强电子耦合（图1 b-c）。本发明使用压延预处理，然后进行透明胶带剥离，首次成功地获得了多种材料的少层甚至单层结构，并且能够在剥离的2D材料中观察到令人兴奋的新现象。金属锑变成了带隙为2.01 eV的半导体；半导体SnO的光吸收范围能够从红外区（IR）调控到紫外区，带隙从块体的0.60 eV调控为单层的3.65 eV。此外，薄KV ₃Sb ₅是一种有潜力的二维超导体。因此，本发明的新结果为非范德华层状材料的机械分层提出了一个通用方法，并提供了多种新的2D材料。 The exfoliation energy of non-van der Waals layered structures is usually several times higher than that of graphite (Figure 1a), which naturally makes exfoliation of these materials difficult. The method of the present invention involves a simple calendering pretreatment, followed by mechanical peeling using transparent tape to obtain thin layers, successfully peeling off a variety of materials, including metals (Bi, Sb), semiconducting metal oxides and chalcogenides (SnO, V ₂ O ₅ , Bi ₂ O ₂ Se) and superconducting compounds (KV ₃ Sb ₅ ), electron density calculations verified the existence of strong electronic coupling between these structural layers (Figure 1 bc). The present invention uses calendering pretreatment followed by transparent tape peeling to successfully obtain few-layer or even single-layer structures of a variety of materials for the first time, and is able to observe exciting new phenomena in the peeled 2D materials. Metal antimony becomes a semiconductor with a band gap of 2.01 eV; the light absorption range of the semiconductor SnO can be adjusted from the infrared region (IR) to the ultraviolet region, and the band gap is adjusted from 0.60 eV in the bulk to 3.65 eV in the single layer. Furthermore, thin KV ₃ Sb ₅ is a potential two-dimensional superconductor. Therefore, the new results of the present invention propose a general method for the mechanical delamination of non-van der Waals layered materials and provide a variety of new 2D materials.

SnCl ₂•2H ₂O（AR，98%）和NaOH（AR，96%）购自国药集团化学试剂有限公司。V ₂O ₅（金属基，99.99%）、Bi（金属基，99.99%）和Sb（金属基，99.99%）的晶体购自阿拉丁实业有限公司（中国上海）。Bi ₂O ₂Se（金属基，99.99%）购自南京米牧科科技有限公司（有限公司）。所有试剂无需纯化。透明胶带购自泰州巨纳新能源有限公司。热释放胶带（单面，热释放温度120℃）购自江苏先丰纳米材料科技有限公司。聚二甲基硅氧烷薄膜（0.5 mm厚）购自洛阳艾特梅尔商贸有限公司。Si/SiO ₂衬底（SiO ₂厚度：300 nm）由北京中镜科仪技术有限公司提供。 SnCl ₂ •2H ₂ O (AR, 98%) and NaOH (AR, 96%) were purchased from Sinopharm Chemical Reagent Co., Ltd. Crystals of V ₂ O ₅ (metal-based, 99.99%), Bi (metal-based, 99.99%), and Sb (metal-based, 99.99%) were purchased from Aladdin Industrial Co., Ltd. (Shanghai, China). Bi ₂ O ₂ Se (metal base, 99.99%) was purchased from Nanjing Mimuke Technology Co., Ltd. (Co., Ltd.). All reagents require no purification. Transparent tape was purchased from Taizhou Juna New Energy Co., Ltd. Thermal release tape (single-sided, heat release temperature 120°C) was purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd. Polydimethylsiloxane film (0.5 mm thick) was purchased from Luoyang Atmel Trading Co., Ltd. Si/ _SiO substrate ( _SiO thickness: 300 nm) was provided by Beijing Zhongjing Keyi Technology Co., Ltd.

材料测试。使用粉末X射线衍射***（XRD，X'Pert-Pro MPD）配备Cu/Kα1靶（λ=1.5418Å）研究了样品的晶体结构。通过扫描电子显微镜（SEM，Hitachi SU8010）研究样品形态。在超高真空条件下，使用Escalab 250Xi X射线光电子能谱仪（Thermo Fisher Scientific Inc.）上的X射线光电子能谱仪（XPS）的Al/Kα靶测试样品的表面化学态，结合能的标准偏差为0.1 eV。原子力显微镜（AFM；Bruker Instruments Dimension ion）用于表征硅衬底上薄片的横向尺寸和厚度。使用FEI Tecnai G2 F20 S-TWIN TMP进行高分辨率透射电镜（HR-TEM），该TMP配备了在200 kV加速电压下工作的场发射枪。机械剥离的薄片直接转移到铜栅极上，使用Themis像差校正扫描透射电子显微镜（STEM，HF5000）采集原子图像，并通过聚焦离子束（FIB）制备样品，其中使用高电流镓离子束剥离表面原子以完成微纳表面形貌加工。在20/30 PV上记录了透明石英载玻片上剥离薄片的紫外-可见近红外透射光谱，环境温度下的微分光光度计（Craic Technologies Inc.），从中使用Tauc图计算带隙值，测量波长范围为350-2000 nm，使用配备UHTS 300光谱仪（每毫米光栅600行）和CCD检测器（DU401A-BV-352）的共聚焦拉曼光谱仪（WITec Alpha 300R），在532 nm激光激发（功率：1 mW）下收集拉曼光谱，光斑半径为2μm。使用100×物镜聚焦激光束并采集拉曼信号，将剥离薄片转移到Si/SiO ₂基板上。 Material testing. The crystal structure of the samples was studied using a powder X-ray diffraction system (XRD, X'Pert-Pro MPD) equipped with a Cu/Kα1 target (λ = 1.5418 Å). The sample morphology was studied by scanning electron microscopy (SEM, Hitachi SU8010). The surface chemical state of the sample was measured using an Al/Kα target of an X-ray photoelectron spectrometer (XPS) on an Escalab 250Xi X-ray photoelectron spectrometer (Thermo Fisher Scientific Inc.) under ultra-high vacuum conditions, and the binding energy standard The deviation is 0.1 eV. Atomic force microscopy (AFM; Bruker Instruments Dimension ion) was used to characterize the lateral dimensions and thickness of flakes on silicon substrates. High-resolution transmission electron microscopy (HR-TEM) was performed using an FEI Tecnai G2 F20 S-TWIN TMP equipped with a field emission gun operating at an accelerating voltage of 200 kV. Mechanically exfoliated flakes were transferred directly to a copper grid, atomic images were collected using a Themis aberration-corrected scanning transmission electron microscope (STEM, HF5000), and samples were prepared by focused ion beam (FIB), in which a high-current gallium ion beam was used to exfoliate the surface. atoms to complete micro-nano surface topography processing. UV-visible near-infrared transmission spectra of exfoliated flakes on clear quartz slides were recorded on a 20/30 PV microspectrophotometer (Craic Technologies Inc.) at ambient temperature, from which band gap values were calculated using Tauc plots, and wavelengths were measured Range 350-2000 nm, using a confocal Raman spectrometer (WITec Alpha 300R) equipped with a UHTS 300 spectrometer (600 lines per mm grating) and a CCD detector (DU401A-BV-352), with laser excitation at 532 nm (power: Raman spectra were collected at 1 mW) with a spot radius of 2 μm. Use a 100× objective lens to focus the laser beam and collect the Raman signal, and transfer the exfoliated flake to the Si/SiO _substrate .

合成例：SnO晶体颗粒的制备。在典型过程中，搅拌下将0.02 mol（4.50 g）SnCl ₂•2H ₂O溶解在70 mL超纯水中，然后添加NaOH，直到混合物的pH值达到9。进一步搅拌30分钟后，将混合物转移到100 mL聚四氟乙烯内衬高压釜中，密封，并在150℃下加热15小时。然后让自然冷却至室温。通过离心混合物收集产品，用蒸馏水和无水乙醇交替洗涤3次，然后在真空中干燥过夜，得到蓝黑色SnO晶体。 Synthesis example: Preparation of SnO crystal particles. In a typical procedure, 0.02 mol (4.50 g) SnCl ₂ •2H ₂ O is dissolved in 70 mL of ultrapure water with stirring, and then NaOH is added until the pH of the mixture reaches 9. After a further 30 min of stirring, the mixture was transferred to a 100 mL Teflon-lined autoclave, sealed, and heated at 150 °C for 15 h. Then let cool naturally to room temperature. The product was collected by centrifuging the mixture, washed three times with distilled water and absolute ethanol alternately, and then dried in vacuum overnight to obtain blue-black SnO crystals.

采用助熔剂法制备了单晶KV ₃Sb ₅，其以KSb ₂合金为助熔剂生长。K、V、Sb元素和KSb ₂前体以1:3:14:10的摩尔比密封在钽坩埚中，然后密封在高度真空的石英安瓿中。将安瓿加热至1273 K，保持20小时，然后冷却至773 K。通过离心分离从助熔剂中分离出横向尺寸约1000μm、具有银色光泽的单晶。 Single crystal KV ₃ Sb ₅ was prepared by flux method, and it was grown using KSb ₂ alloy as flux. K, V, Sb elements and KSb _precursors were sealed in a tantalum crucible at a molar ratio of 1:3:14:10, and then sealed in a high vacuum quartz ampoule. The ampoule was heated to 1273 K, held for 20 hours, and then cooled to 773 K. A single crystal with a lateral size of about 1000 μm and a silver luster is separated from the flux by centrifugal separation.

本发明首先将晶体颗粒压延，然后通过透明胶带对颗粒进行机械剥离来制备，使用现有技术的全干法技术转移到目标基板上。作为示例，本发明将晶体颗粒平铺后，在表面上滚压，即在晶体上施加剪切力，滚压仅在一个方向上（不是来回滚压），从而导致连续和单向的压延，滚轮或者棒荷重为0.5～10kg，速度为10～500mm/min。然后根据常规方法进行：使用透明胶带剥离辊压后的晶体颗粒，得到薄层（即本发明的产品二维纳米片），再使用热释放胶带将薄层从透明胶带上分离，然后通过加热释放将薄层转移到聚二甲基硅氧烷膜上，还可进一步将胶带垂直压在目标基板上，将剥离的薄片转移到各种基板上，例如玻璃、硅或硅/二氧化硅；也可以省略使用热释放胶带和/或聚二甲基硅氧烷膜的转移步骤。本发明中，具体平铺方法为常规技术，没有限定，不影响本发明技术效果的实现。The present invention first calenders crystal particles, and then mechanically peels off the particles through transparent tape, and then transfers them to the target substrate using the existing all-dry technology. As an example, the present invention tiles the crystal particles and then rolls them on the surface, that is, applying shear force on the crystals. The rolling is only in one direction (not back and forth), resulting in continuous and unidirectional rolling. The load of the roller or rod is 0.5~10kg, and the speed is 10~500mm/min. Then proceed according to the conventional method: use transparent tape to peel off the rolled crystal particles to obtain a thin layer (i.e., the two-dimensional nanosheet of the product of the present invention), then use thermal release tape to separate the thin layer from the transparent tape, and then release it by heating Transfer the lamella to a polydimethylsiloxane film and further transfer the exfoliated lamella to various substrates such as glass, silicon or silicon/silica by pressing the tape vertically against the target substrate; also The transfer step using heat release tape and/or polydimethylsiloxane membrane can be omitted. In the present invention, the specific tiling method is a conventional technique and is not limited, and does not affect the realization of the technical effects of the present invention.

实施例一：将晶体颗粒夹在两张纸之间，然后在表面上手压单向滚动一根塑料棒，得到压延颗粒；再使用常规的经典的胶带剥离法，即：透明胶带粘压延颗粒，对折按压后撕开形成剥离，得到薄层材料，即本发明的产品二维纳米片。然后100℃烘5秒（利于薄片保持横向尺寸），再使用热释放胶带将薄层从透明胶带上分离，后根据测试需要，在150℃下释放，将薄片转移至不同基底上。Example 1: Sandwich the crystal particles between two pieces of paper, and then roll a plastic rod on the surface by hand in one direction to obtain the calendered particles; then use the conventional classic tape peeling method, that is, stick the calendered particles with transparent tape, Fold in half and press, then tear to form peeling, and obtain a thin layer of material, that is, the two-dimensional nanosheet of the product of the present invention. Then bake it at 100°C for 5 seconds (to help the sheet maintain its lateral dimensions), then use thermal release tape to separate the thin layer from the transparent tape, and then release it at 150°C according to test needs, and transfer the sheet to different substrates.

晶体颗粒分别为金属Bi、金属Sb、半导体金属氧化物SnO、V ₂O ₅、Bi ₂O ₂Se、超导化合物KV ₃Sb ₅。 The crystal particles are metal Bi, metal Sb, semiconductor metal oxide SnO, V ₂ O ₅ , Bi ₂ O ₂ Se, and superconducting compound KV ₃ Sb ₅ .

实施例二 SnO二维纳米片的性能表征。Example 2 Performance characterization of SnO two-dimensional nanosheets.

SnO的晶体结构属于P4/nmm空间群，具有四方晶胞结构，Sn和O原子以Sn _1/2−O−Sn _1/2顺序沿[001]晶体方向交替排列形成层状序列（图2a）。每个O原子与四个表面金属Sn原子配位，形成Sn ₄O四面体。因此，由Sn 5s轨道构成的孤对电子指向层间间距，因此相邻SnO层之间存在强烈的偶极-偶极相互作用。该结构的微分电荷密度图显示层间的高电子密度，表明存在强层间相互作用（图2b）。由于具有48.4 meVÅ ^-2的高剥离能的相邻层之间的强结合相互作用（通过块体材料和单层之间基态能量的差异进行量化，为现有技术），无法通过现有的机械剥离产生单层薄片。本发明从SnO晶体颗粒上剥离一个单层的SnO薄片，该纳米薄片具有一种不寻常的金属覆盖结构，其中两个Sn原子层夹住一个O原子层。SnO单层的晶体学厚度为0.38 nm。计算的单层SnO声子谱表明，整个Brillouin区的所有声子分支均为正，不存在虚频（图2c），表明2D SnO薄片在基态下的结构稳定性。进一步研究了这种单层纳米片对环境或氧化环境和温度的稳定性，因为这对基础研究和技术应用至关重要。通过使用DFT计算的爬坡弹性带法对氧化势垒的理论估计表明，SnO薄片具有稳定性，能够抵抗O ₂攻击（图2e）。在300和600 K温度下的分子动力学模拟表明，没有明显的结构离解（图2d），表明SnO剥离薄片具有较高的热稳定性。这些发现有力地表明，一旦从大块晶体的堆叠层中分离出来，单层的2D SnO是稳定的。 The crystal structure of SnO belongs to the P4/nmm space group and has a tetragonal unit cell structure. Sn and O atoms are alternately arranged in the order of Sn _1/2 −O−Sn _1/2 along the [001] crystal direction to form a layered sequence (Figure 2a) . Each O atom is coordinated with four surface metal Sn atoms to form a Sn ₄ O tetrahedron. Therefore, the lone pair electrons composed of Sn 5s orbitals are directed towards the interlayer spacing, so there is a strong dipole-dipole interaction between adjacent SnO layers. The differential charge density map of this structure shows high electron density between layers, indicating the presence of strong interlayer interactions (Figure 2b). Due to the strong binding interactions between adjacent layers with a high peeling energy of 48.4 meVÅ ^-2 (quantified by the difference in ground state energy between the bulk material and the monolayer, which is the state of the art), it is not possible to pass the existing mechanical Peeling produces single layer flakes. The invention peels off a single-layer SnO flake from SnO crystal particles. The nanoflake has an unusual metal covering structure, in which two Sn atomic layers sandwich an O atomic layer. The crystallographic thickness of the SnO monolayer is 0.38 nm. The calculated phonon spectrum of single-layer SnO shows that all phonon branches throughout the Brillouin zone are positive and there is no imaginary frequency (Figure 2c), indicating the structural stability of the 2D SnO flake in the ground state. The stability of this single-layer nanosheet to ambient or oxidizing environments and temperatures was further investigated, as this is crucial for fundamental research and technological applications. Theoretical estimation of the oxidation barrier by the climbing elastic band method using DFT calculations shows that the SnO flakes are stable and resistant to O attack (Fig. _2e ). Molecular dynamics simulations at temperatures of 300 and 600 K showed no obvious structural dissociation (Fig. 2d), indicating the high thermal stability of SnO exfoliated flakes. These findings strongly suggest that single layers of 2D SnO are stable once separated from the stacked layers of bulk crystals.

本发明通过氯化亚锡二水合物和氢氧化钠的水热反应制备了SnO晶体颗粒（详细信息见合成例）。水热反应后晶体的X射线衍射图（XRD）显示衍射峰，可以用晶格参数索引到四方晶胞：a=b=3.8016（4）Å，c=4.8441（5）Å（图3a），表明在这些条件下形成纯相SnO。X射线光电子能谱（XPS）证实了Sn和O元素的存在，Sn/O比接近1。高分辨率Sn 3d光谱在486.1和494.5 eV处显示两个显著的峰值，分别对应于Sn ²⁺的Sn 3d _5/2和Sn 3d _3/2核心能级。价态也与晶体的蓝黑色一致（插图见图3a）。原始晶体的拉曼光谱显示E _g在112 cm ^-1处，A _1g峰在210 cm ^-1处，这是SnO结构的特征（图3b）。扫描电子显微镜（SEM）显示，SnO晶体横向尺寸为100μm，厚度约为10μm（图3c）。片状形状可能与固有的各向异性层状结构有关，其厚度与片层堆垛有关。对这些晶体进行简单的压延处理可使得SnO晶体结构变化，称为M-SnO。SEM的形态表征显示了平面的滑动（图3d），在XRD图案的低角度区域观察到一个新的衍射峰，表明层间距从4.844Å略微增加到4.949Å（图3a）。图3e为原位AFM。图3f扫描透射电子显微镜（STEM）显示相邻层之间的排斥，并增加沿堆叠方向的重复距离。在Sn位点未观察到空位。平面内Sn-Sn距离从2.684Å略微变化到2.715Å，这与XRD结果一致。在压延处理后，平面内拉曼振动模式E _g的强度显著降低（图3b）。 The present invention prepares SnO crystal particles through the hydrothermal reaction of stannous chloride dihydrate and sodium hydroxide (see synthesis examples for details). The X-ray diffraction pattern (XRD) of the crystal after the hydrothermal reaction shows diffraction peaks, which can be indexed to the tetragonal unit cell using the lattice parameters: a=b=3.8016(4)Å, c=4.8441(5)Å (Fig. 3a), It was shown that pure phase SnO is formed under these conditions. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Sn and O elements, and the Sn/O ratio was close to 1. The high-resolution Sn 3d spectrum shows two significant peaks at 486.1 and 494.5 eV, corresponding to the Sn 3d _5/2 and Sn 3d _3/2 core energy levels of Sn ²⁺ , respectively. The valence state is also consistent with the blue-black color of the crystal (see Figure 3a for an illustration). The Raman spectrum of the original crystal shows E _g at 112 cm ⁻¹ and A _1g peak at 210 cm ⁻¹ , which are characteristic of the SnO structure (Fig. 3b). Scanning electron microscopy (SEM) shows that the lateral size of SnO crystals is 100 μm and the thickness is about 10 μm (Figure 3c). The sheet-like shape may be related to the intrinsic anisotropic layered structure, and its thickness is related to the stacking of sheets. A simple rolling process on these crystals can change the SnO crystal structure, which is called M-SnO. Morphological characterization by SEM showed slipping of the planes (Fig. 3d), and a new diffraction peak was observed in the low-angle region of the XRD pattern, indicating a slight increase in the layer spacing from 4.844Å to 4.949Å (Fig. 3a). Figure 3e shows in situ AFM. Figure 3f Scanning transmission electron microscopy (STEM) shows repulsion between adjacent layers and increases the repeating distance along the stacking direction. No vacancies were observed at the Sn site. The in-plane Sn-Sn distance slightly changes from 2.684Å to 2.715Å, which is consistent with the XRD results. After the calendering process, the intensity of the in-plane Raman vibration mode E _g is significantly reduced (Fig. 3b).

本发明公开的方法中，压延处理后，可使用常规的透明胶带方法将晶体剥离分层成单个SnO薄片；转移到透明玻璃基板上的剥离SnO薄片的光学显微镜图像显示具有高透明度（图4a）。通过AFM验证层数，如图4b-f所示。AFM测量的二维SnO薄片的最小厚度为0.8 nm，基于其晶体结构，SnO单层的厚度为0.38 nm，考虑到通常存在于剥离片和基板之间的0.1-0.6nm的界面“无效层”，测量的0.8nm高度不能对应于两或更多层，而应对应于单层SnO。测量了不同厚度的层，具体为1.3、1.8、2.4和2.9 nm，厚度在约0.5 nm的步骤中增加，如图4c插图所示，理想的步长是相邻层的结晶重复距离（0.48 nm），与实验测量的步长值完全匹配，因此，这些薄片对应于层数2、3、4和5。本发明剥离片尺寸为微米级，单层片的尺寸为2～6μm，5层薄片尺寸增加到约15μm（图4b-i），能够满足对固有材料特性和某些器件进行基础研究应用。高分辨率透射电子显微镜（TEM）显示间距为2.7Å的交叉晶格条纹，对应于（110）平面的晶格条纹间距（图4g）。仔细检查图像没有发现明显的缺陷，表明在压延过程中没有产生过多的金属空位缺陷。在拉曼光谱中，平面内振动模式E _g的强度随着样品厚度的减小而迅速减小，对于单层几乎无法检测到（图4h），A _1g峰出现红移（~4cm ^-1），随着层数的减少，层状结构中的振动模式软化。单个薄片上E _g和A _1g模式的拉曼强度mapping映射进一步证实了厚度和局部键合结构的高度均匀性（图5）。值得注意的是，即使将样品暴露在空气中超过3个月并额外加热到200℃后，也没有观察到SnO ₂的特征峰，这证实了剥离SnO薄片在环境条件下的结构稳定性。AFM研究证实，薄片的形态和厚度保持完整（图6）。 In the method disclosed in the present invention, after the calendering process, the crystal can be exfoliated and stratified into individual SnO flakes using a conventional transparent tape method; the optical microscope image of the exfoliated SnO flakes transferred to a transparent glass substrate shows high transparency (Figure 4a) . The number of layers is verified by AFM, as shown in Figure 4b-f. The minimum thickness of the 2D SnO flakes measured by AFM is 0.8 nm. Based on its crystal structure, the thickness of the SnO monolayer is 0.38 nm, taking into account the 0.1-0.6 nm interface "invalid layer" that usually exists between the exfoliated sheet and the substrate. , the measured height of 0.8nm cannot correspond to two or more layers, but should correspond to a single layer of SnO. Layers of different thicknesses were measured, specifically 1.3, 1.8, 2.4 and 2.9 nm, with the thickness increasing in steps of approximately 0.5 nm, as shown in the inset of Figure 4c, with the ideal step size being the crystallographic repeating distance of adjacent layers (0.48 nm ), exactly matches the experimentally measured step size values, therefore, these lamellae correspond to layer numbers 2, 3, 4 and 5. The size of the peeling sheet of the present invention is in the micron level, the size of the single-layer sheet is 2-6 μm, and the size of the five-layer sheet is increased to about 15 μm (Fig. 4b-i), which can meet the basic research and application of inherent material properties and certain devices. High-resolution transmission electron microscopy (TEM) revealed cross-lattice fringes with a spacing of 2.7 Å, corresponding to the lattice fringe spacing of the (110) plane (Figure 4g). Careful inspection of the images revealed no obvious defects, indicating that excessive metal vacancy defects were not created during the calendering process. In the Raman spectrum, the intensity of the in-plane vibration mode E _g decreases rapidly with decreasing sample thickness and is almost undetectable for a single layer (Fig. 4h), and the A _1g peak appears red-shifted (~4 cm ^-1 ) , as the number of layers decreases, the vibration modes in the layered structure soften. Raman intensity mapping of _the Eg and _A1g modes on a single flake further confirmed the high degree of uniformity in thickness and local bonding structure (Fig. 5). It is worth noting that even after exposing the sample to air for more than 3 months and additional heating to 200 °C, no characteristic peaks of _SnO were observed, which confirms the structural stability of exfoliated SnO flakes under ambient conditions. AFM studies confirmed that the morphology and thickness of the flakes remained intact (Figure 6).

块体SnO晶体剥离成薄片后，其物理性质发生了显著变化。理论预测表明，带隙从块体SnO的0.64 eV显著增加到单层的3.95 eV（图7a）。实验上，SnO薄片的吸收光谱显示出具有明显吸收边缘的半导体的形状特征（图8），与理论估计一致。随着纳米片厚度的降低，SnO薄片的带隙不断增加（图7b），带隙调制跨越了从红外到紫外的整个光谱范围，这一非常宽的吸收窗口是迄今为止报道的2D半导体最大的吸收窗口（图7e）。After bulk SnO crystals are peeled off into thin sheets, their physical properties change significantly. Theoretical predictions show that the band gap increases significantly from 0.64 eV in bulk SnO to 3.95 eV in the monolayer (Fig. 7a). Experimentally, the absorption spectrum of SnO flakes shows the shape characteristics of a semiconductor with a clear absorption edge (Figure 8), consistent with theoretical estimates. As the nanosheet thickness decreases, the band gap of SnO flakes continues to increase (Figure 7b). The band gap modulation spans the entire spectral range from infrared to ultraviolet. This very wide absorption window is the largest reported so far for 2D semiconductors. absorption window (Fig. 7e).

使用仪器上的光学显微镜附件，根据基板和分层板之间的对比度差异选择适当的样品位置。与高透明度的剥离后薄片相比，原始大块晶体由于不透明而呈黑色。较薄的薄片显示出更高的透明度。基于（αhv） ^1/2与hv的Tauc图，其中 α代表吸光系数， h是普朗克常数， ν是入射光子频率，通过将拟合线外推到截距（α=0）来提取光学带隙值。 Using the light microscope accessory on the instrument, select the appropriate sample position based on the contrast difference between the substrate and the layered plate. Compared with the highly transparent exfoliated flakes, the original bulk crystals appear black due to opacity. Thinner flakes show greater transparency. Based on the Tauc plot of (αhv) ^1/2 vs. hv, where α represents the absorption coefficient, h is Planck's constant and ν is the incident photon frequency, the optics are extracted by extrapolating the fitted line to the intercept (α=0) Bandgap value.

实施例三通过本发明获得的其他材料薄片的物理特性。Example 3 Physical properties of other material sheets obtained by the present invention.

本发明可适用于多种材料，包括金属（Bi、Sb）、半导体金属氧化物和硫族化合物（SnO、V ₂O ₅、Bi ₂O ₂Se）以及超导化合物（KV ₃Sb ₅）；层间相互作用和相应的AFM图像如图1b和c所示。具体来说，金属锑（Sb）是一种三维伪层状晶体，属于 R3-mh空间群，具有三角和六角晶格。该晶体可视为锑原子弯曲蜂窝排列的ABCABC堆叠层。值得注意的是，最小层间距仅为0.23 nm，这意味着层间相互作用主要是化学相互作用（图1b中的结构和密度图），这使得直接机械剥离很难实现。使用本发明的方法，可以得到1.2 nm厚的Sb单层。图9-13给出了锑和其他示例材料的表征细节。从这些材料（包括Bi、Sb和Bi ₂O ₂Se）上剥离的纳米片，即使在空气中额外加热，也表现出长时间抗氧化的稳定性（图14-16）。重要的是，当减薄到1.2 nm厚的单层时，金属锑转化为宽带隙半导体（2.01 eV）（图7c，d）。本发明得到与厚度相关的物理性质的广泛调制可能与层间区域中的强电子耦合有关。在非范德华结构中，随着层数的减少，强烈的层间相互作用会导致晶格结构发生细微变化，这除了尺寸效应外，还影响剥离薄片的物理性质，在这些材料中观察到的独特厚度-性能关系进一步突出了将2D薄片扩展到非范德华材料的重要性。 The present invention can be applied to a variety of materials, including metals (Bi, Sb), semiconductor metal oxides and chalcogen compounds (SnO, V ₂ O ₅ , Bi ₂ O ₂ Se) and superconducting compounds (KV ₃ Sb ₅ ); The interlayer interactions and corresponding AFM images are shown in Figure 1b and c. Specifically, metallic antimony (Sb) is a three-dimensional pseudo-layered crystal that belongs to the R 3-mh space group and has triangular and hexagonal lattice. The crystal can be viewed as an ABCABC stack of antimony atoms arranged in a curved honeycomb arrangement. It is worth noting that the minimum interlayer spacing is only 0.23 nm, which means that the interlayer interactions are mainly chemical interactions (structure and density map in Figure 1b), which makes direct mechanical exfoliation difficult to achieve. Using the method of the present invention, a 1.2 nm thick Sb monolayer can be obtained. Characterization details for antimony and other example materials are given in Figures 9-13. Nanosheets exfoliated from these materials, including Bi, Sb, and Bi ₂ O ₂ Se, exhibit long-term stability against oxidation even with additional heating in air (Figure 14-16). Importantly, metallic antimony transforms into a wide bandgap semiconductor (2.01 eV) when thinned to a 1.2 nm thick monolayer (Fig. 7c,d). The broad modulation of thickness-dependent physical properties achieved by the present invention may be related to the strong electronic coupling in the interlayer region. In non-van der Waals structures, strong interlayer interactions lead to subtle changes in the lattice structure as the number of layers decreases, which, in addition to size effects, affects the physical properties of the exfoliated flakes, uniquely observed in these materials. The thickness-property relationship further highlights the importance of extending 2D flakes to non-van der Waals materials.

KV ₃Sb ₅是最近发现的准二维Kagome金属家族的一员，其通式为AV ₃Sb ₅（a:K，Rb，Cs）。该材料属于P6/mmm空间群，各层通过A和V之间的化学键连接。过渡金属原子的Kagome晶格被视为研究一系列电子关联现象的激发平台，包括电荷密度波、异常霍尔效应和超导性，并产生令人惊讶的结果。与块体材料相比，2D结构具有几个优点：二维几何形状将增强量子涨落和相关性，并且还可以通过载流子掺杂促进电荷调制，所有这些都可能改变超导性和电荷密度波。例如，对于CsV ₃Sb ₅，对于厚度为60 nm的薄片，超导转变温度Tc从块状的约2.5 K增加到4.28 K，然而当样品进一步减薄到4.8 nm时观察到相反的行为，即Tc降低到0.76 K。电荷密度波转变温度随厚度的变化趋势相反。利用表面A层的反应性，最近的一项工作报告了通过简单地将Cs层暴露在空气中几分钟，通过Cs层的自然氧化进行空穴掺杂。对于厚度小于82 nm的片层， T _c显著跃升至约4.7 K。KV ₃Sb ₅本体的Tc较低，为0.93 K，由于Cs上的价电子很容易失去，K相关材料可能是更有效地调节载流子浓度的更好平台。薄KV ₃Sb ₅晶体（厚度约105 nm）的反常霍尔电导率高达15507 ohm ^-1 cm ^-1。关于这类材料的剥离，据报道，使用常规的、传统的透明胶带法不能将CsV ₃Sb ₅晶体减薄到纳米级（100nm以下），这归因于Sb和Cs层之间的化学相互作用；K的尺寸比Cs小，这意味着KV ₃Sb ₅中的结合相互作用更强，使其剥离更加困难。出乎意料的，使用本发明的压延结合常规胶带剥离，获得了厚度为2～5nm的KV ₃Sb ₅薄片，对应于2～5层（图1c和17）。即使在环境条件下暴露于空气中至少10分钟，5.4 nm的薄片也具有相当光滑的表面，KV ₃Sb ₅成功剥离到单层或少层将为研究非常规超导性以及与二维Kagome晶格中电荷密度波的相互作用提供新的机会。 KV ₃ Sb ₅ is a member of the recently discovered quasi-two-dimensional Kagome metal family, and its general formula is AV ₃ Sb ₅ (a:K, Rb, Cs). The material belongs to the P6/mmm space group, and the layers are connected by chemical bonds between A and V. Kagome lattices of transition metal atoms are viewed as an exciting platform to study a range of electronically correlated phenomena, including charge density waves, the anomalous Hall effect and superconductivity, with surprising results. 2D structures have several advantages over bulk materials: the two-dimensional geometry will enhance quantum fluctuations and correlations, and can also facilitate charge modulation through carrier doping, all of which may alter superconductivity and charge Density waves. For example, for CsV ₃ Sb ₅ , the superconducting transition temperature Tc increases from about 2.5 K in bulk to 4.28 K for flakes with a thickness of 60 nm, however the opposite behavior is observed when the sample is further thinned to 4.8 nm, i.e. Tc decreases to 0.76 K. The charge density wave transition temperature has an opposite trend with thickness. Taking advantage of the reactivity of the surface A-layer, a recent work reported hole doping through natural oxidation of the Cs layer by simply exposing it to air for several minutes. _For lamellae less than 82 nm thick, T jumps significantly to about 4.7 K. The KV ₃ Sb ₅ bulk has a lower Tc of 0.93 K, and since valence electrons on Cs are easily lost, K-related materials may be a better platform to tune the carrier concentration more efficiently. The anomalous Hall conductivity of thin KV ₃ Sb ₅ crystals (thickness about 105 nm) is as high as 15507 ohm ^-1 cm ^-1 . Regarding the exfoliation of this type of material, it has been reported that CsV ₃ Sb ₅ crystals cannot be thinned to the nanometer scale (below 100 nm) using the regular, traditional Scotch tape method, which is attributed to the chemical interaction between the Sb and Cs layers. ;The size of K is smaller than _Cs , which means the binding interactions in _KV3Sb5 are stronger, making it more difficult to peel off. Unexpectedly, using the inventive calendering combined with conventional tape peeling, KV ₃ Sb ₅ flakes with a thickness of 2 to 5 nm were obtained, corresponding to layers 2 to 5 (Figs. 1c and 17). The 5.4 nm flakes have a fairly smooth surface even when exposed to air for at least 10 minutes under ambient conditions. Successful exfoliation of KV ₃ Sb ₅ into single or few layers will provide valuable insights into the study of unconventional superconductivity and its interaction with two-dimensional Kagome crystals. The interaction of charge density waves in the lattice provides new opportunities.

应用实施例：将晶体颗粒平铺在电动碾压滚轮（HZ-2403）的底板上，以200 mm/min单向单轮压延，得到压延颗粒；再使用透明胶带粘压延颗粒，对折按压后撕开形成剥离，得到薄层材料，即本发明的产品二维纳米片。晶体颗粒分别为金属Bi、金属Sb、半导体金属氧化物SnO、V ₂O ₅、Bi ₂O ₂Se、超导化合物KV ₃Sb ₅，得到的二维纳米片与实施例一近似，包括单层或者少层剥离薄片，横向尺寸也可以达到15 μm。说明本发明方法不仅具有对多种晶体颗粒的普适性，而且可利用工业设备进行制备，为工业化提供基础。 Application Example: Lay the crystal particles flat on the bottom plate of the electric rolling roller (HZ-2403), and roll it in one direction and one wheel at 200 mm/min to obtain the rolled particles; then use transparent tape to stick the rolled particles, fold it in half, press it, and then tear it off It is peeled off to obtain a thin layer of material, that is, the two-dimensional nanosheet of the product of the present invention. The crystal particles are metal Bi, metal Sb, semiconductor metal oxide SnO, V ₂ O ₅ , Bi ₂ O ₂ Se, and superconducting compound KV ₃ Sb ₅ respectively. The obtained two-dimensional nanosheet is similar to Example 1, including a single layer Or few-layer exfoliated flakes, the lateral size can also reach 15 μm. It shows that the method of the present invention not only has universal applicability to a variety of crystal particles, but can also be prepared using industrial equipment, providing a basis for industrialization.

总之，本发明提出了一种通用方案，用于具有非范德华型层间力的各种晶体结构的机械剥离，包括金属（Bi、Sb）、半导体金属氧化物和硫族化合物（SnO、V ₂O ₅、Bi ₂O ₂Se）以及超导化合物（KV ₃Sb ₅）。通过简单的压延，成功实现了机械剥离。来自非范德华结构的新2D片材显示出明显好的、区别与晶体块材的物理性质；带隙可以从块体SnO的0.60 Ev (IR)调节到单层的3.65 eV（UV）；块体Sb过渡到单层时发生金属-半导体（2.01 eV带隙）转变。在这项工作中获得的单层和少层KV ₃Sb ₅是2D超导体的令人振奋的产品。本发明首次提出了一种将非范德华层状结构机械剥离为高质量2D类似物的方法，并为易于制备具有潜在应用的新材料家族打开了大门。 In conclusion, the present invention presents a general scheme for the mechanical exfoliation of various crystal structures with non-van der Waals type interlayer forces, including metals (Bi, Sb), semiconducting metal oxides and chalcogenides (SnO, _V O ₅ , Bi ₂ O ₂ Se) and superconducting compounds (KV ₃ Sb ₅ ). Mechanical peeling was successfully achieved through simple calendering. New 2D sheets from non-van der Waals structures show significantly better physical properties that are different from those of crystalline bulk; the bandgap can be tuned from 0.60 Ev (IR) of bulk SnO to 3.65 eV (UV) of a single layer; bulk A metal-semiconductor (2.01 eV band gap) transition occurs when Sb transitions to a monolayer. The single- and few-layer KV ₃ Sb ₅ obtained in this work are exciting products for 2D superconductors. The present invention proposes for the first time a method to mechanically exfoliate non-van der Waals layered structures into high-quality 2D analogs and opens the door to the easy preparation of a new family of materials with potential applications.

对比例：采用常规的胶带剥离法：使用透明胶带直接粘SnO晶体颗粒（未压延），对折按压后撕开形成剥离，得到剥离产物。图18为以透射模式采集的载玻片基板上胶带剥离SnO片的光学显微图像示例，可看出这些分层晶体仍然很厚且不透明，厚度在微米级，说明常规胶带剥离无法得到二维片材，更无法得到厚度为纳米级的薄片。Comparative Example: The conventional tape peeling method is used: use transparent tape to directly stick SnO crystal particles (not calendered), fold it in half and press it, then tear it to form peeling, and obtain the peeling product. Figure 18 is an example of an optical microscopy image of tape-stripped SnO flakes on a glass slide substrate collected in transmission mode. It can be seen that these layered crystals are still very thick and opaque, with thicknesses in the micron range, indicating that conventional tape peeling cannot obtain two-dimensional Sheets, let alone nanometer-thick sheets, cannot be obtained.

金属（Bi、Sb）、V ₂O ₅、Bi ₂O ₂Se、超导化合物（KV ₃Sb ₅）采用常规的经典的胶带剥离法无法得到厚度小于0.2μm的片材。 For metals (Bi, Sb), V ₂ O ₅ , Bi ₂ O ₂ Se, and superconducting compounds (KV ₃ Sb ₅ ), sheets with a thickness less than 0.2 μm cannot be obtained using the conventional classic tape peeling method.

单层厚度下的二维（2D）材料具有许多新性能和厚度相关性。层状结构的机械剥离是获得超薄片的最有效方法，但这种方法仅限于层间相互作用由弱范德华力控制的材料，对于非范德华结构的材料不适用。本发明首次公开了一种机械剥离非范德华结构的通用方法，以获得多种新型二维材料，包括金属（Bi、Sb）、半导体金属氧化物和硫系化合物（SnO、V ₂O ₅、Bi ₂O ₂Se）以及超导化合物（KV ₃Sb ₅）。本发明的方法涉及压延原料，然后使用典型的透明胶带方法对滑动后的结构进行机械剥离，得到稳定的单层或数层材料，具有令人兴奋的新物理性质。例如，金属和半导体的带隙根据层数在很宽的范围内进行调制（Sb为0至2.01 eV，SnO为0.60 eV（IR）至3.65 eV（UV））。还获得了几层KV ₃Sb ₅，是研究非常规超导电性的一种激动人心的材料。本发明新的直接机械剥离非范德华层状材料的方法大大拓宽了2D材料的可用性，以探索其独特的物理特性和实际应用。 Two-dimensional (2D) materials under a single layer thickness have many new properties and thickness dependencies. Mechanical exfoliation of layered structures is the most effective method to obtain ultrathin sheets, but this method is limited to materials where interlayer interactions are controlled by weak van der Waals forces and is not applicable to materials with non-van der Waals structures. The present invention discloses for the first time a general method for mechanically stripping non-van der Waals structures to obtain a variety of new two-dimensional materials, including metals (Bi, Sb), semiconductor metal oxides and chalcogenide compounds (SnO, V ₂ O ₅ , Bi ₂ O ₂ Se) and superconducting compounds (KV ₃ Sb ₅ ). The method of the invention involves calendering the raw material and then mechanically peeling off the slid structure using a typical Scotch tape method, resulting in a stable single layer or several layers of material with exciting new physical properties. For example, the band gaps of metals and semiconductors are modulated over a wide range depending on the number of layers (0 to 2.01 eV for Sb, 0.60 eV (IR) to 3.65 eV (UV) for SnO). Several layers of KV ₃ Sb ₅ were also obtained, an exciting material for studying unconventional superconductivity. The present invention's new direct mechanical exfoliation method of non-van der Waals layered materials greatly broadens the availability of 2D materials to explore their unique physical properties and practical applications.

Claims

一种二维纳米片的制备方法，其特征在于，将晶体颗粒压延处理，然后机械剥离，得到二维纳米片。A method for preparing two-dimensional nanosheets, which is characterized by rolling crystal particles and then mechanically peeling them off to obtain two-dimensional nanosheets.
根据权利要求1所述二维纳米片的制备方法，其特征在于，所述晶体颗粒为非范德华层状晶体颗粒。The method for preparing two-dimensional nanosheets according to claim 1, wherein the crystal particles are non-van der Waals layered crystal particles.
根据权利要求2所述二维纳米片的制备方法，其特征在于，所述非范德华层状晶体颗粒为金属颗粒、金属氧化物半导体颗粒、金属硫化物半导体颗粒、超导化合物颗粒等。The method for preparing two-dimensional nanosheets according to claim 2, wherein the non-van der Waals layered crystal particles are metal particles, metal oxide semiconductor particles, metal sulfide semiconductor particles, superconducting compound particles, etc.
根据权利要求1所述二维纳米片的制备方法，其特征在于，所述晶体颗粒的粒径为微米到毫米级。The method for preparing two-dimensional nanosheets according to claim 1, wherein the particle size of the crystal particles is in the range of micrometers to millimeters.
根据权利要求4所述二维纳米片的制备方法，其特征在于，所述晶体颗粒的粒径为1μm～5mm。The method for preparing two-dimensional nanosheets according to claim 4, wherein the particle size of the crystal particles is 1 μm to 5 mm.
根据权利要求1所述二维纳米片的制备方法，其特征在于，将晶体颗粒平铺后进行压延处理，然后通过机械剥离，得到二维纳米片。The method for preparing two-dimensional nanosheets according to claim 1, characterized in that the crystal particles are flattened, rolled, and then mechanically peeled off to obtain two-dimensional nanosheets.
根据权利要求1所述二维纳米片的制备方法，其特征在于，采用滚轮或者棒进行压延处理；机械剥离为胶带剥离。The method for preparing two-dimensional nanosheets according to claim 1, characterized in that a roller or a rod is used for rolling processing; the mechanical peeling is tape peeling.
根据权利要求1所述二维纳米片的制备方法制备的二维纳米片。Two-dimensional nanosheets prepared according to the method for preparing two-dimensional nanosheets according to claim 1.
根据权利要求8所述二维纳米片，其特征在于，二维纳米片的厚度在0.1nm～50nm。The two-dimensional nanosheet according to claim 8, characterized in that the thickness of the two-dimensional nanosheet is between 0.1nm and 50nm.
权利要求1所述二维纳米片在制备二维纳米片组装体材料中的应用。The application of the two-dimensional nanosheets of claim 1 in the preparation of two-dimensional nanosheet assembly materials.