Chemical Vapor Deposition Growth Of Two-Dimensional Materials And Their Heterostructures

The discovery and development of new materials play an important role in the improvement of human life and the advancement of science and technology.The emergence of graphene has led to an unprecedented revolution in the field of materials science.Compared with other materials,two-dimensional(2D)materials are endowed with lots of unique properties in optical,electrical,mechanical and thermal fields,which has played an enormous role in the development of key areas such as energy,catalysis,integrated circuits,composite materials and quantum communications.Researchers have found that high-quality2D materials not only contribute to the improvement of the application performance in many related fields,but also to the exploration of novel physical phenomena under 2D limits.Among the preparation methods of 2D materials,chemical vapor deposition(CVD)technology is the most promising one for the large-scale,low-cost preparation for high-quality 2D materials.This dissertation developes controllable CVD growth strategies for high-quality 2D materials,and explores the properties and applications of the as-produced2D materials.The major contents and achievements of this dissertation are as follows:(1)The growth of high-quality single-layer graphene single crystals via CVD strategy.The as-grown graphene single crystals were characterized in detail,and it was confirmed that their defects were extremely small and their layer number was uniform.By choosing the appropriate growth parameters,we realized the growth of millimeter-scale graphene single crystals on the liquid Cu surface.This liquid metal CVD strategy for the growth of high-quality large-sized graphene single crystals is expected to be expand to the large-area growth of other high-quality 2D materials.(2)The CVD growth of graphene foam through the employment of Ni foam as growth substrate.Based on the as-obtained multi-layer graphene with porous structure,we achieved the growth of Ni₅P₄ nanoclusters/Ni Co₂O₄ nanosheets on its surface,and explored the application of such composites as electrocatalytic hydrogen evolution catalysts.The results demonstrated that the strong stability,high specific surface areas and excellent conductivity of the graphene foam contribute a lot to the outstanding electrocatalytic performance.We envision that this graphene foam structure could be applied to many other fields such as energy storage and energy conversion.(3)The growth of 2D antimonene oxides via CVD strategy.Detailed characterizations were carried out,which demonstrated that the as-obtained 2D antimonene oxides possess excellent crystallinity and high quality.The precise structure of such 2D antimonene oxides was elucidated through grazing-incidence X-ray diffraction and scanning transmission electron microscopy.Besides,based on the conductive atomic force microscopy characterizations,the as-grown 2D antimonene oxides exhibit excellent insulating capabilities with high dielectric constant(?100)and large breakdown electric field(?5.7GV·m^-1).This CVD strategy can also be utilized to fabricate 2D oxides that are analogues of other 2D Xenes,openning uping a new avenue in broadening the applicaitons of 2D Xenes and their oxides in many emerging fields.(4)The growth of Re S₂/WS₂ vertical heterstructures via CVD strategy.Specifically,we take advantage of the atomic vacancies in liquid Au to accommodate and provide atomic Re and W precursors,which eliminates the transition metal oxide precursors and then avoids the oxide residues.Based on the differences between the adsorption energy of Re and W atoms on Au(111)surface,100%stacked transition metal dichalcogenides(TMDCs)vertical heterostructures were achieved.We have carried out detailed characterizations on the as-obtained Re S₂/WS₂ vertical heterstructures,confirming that they possess the features of clean interface and high stacking percentage.Besides,the Re S₂/WS₂ vertical heterstructures have shown better electrical and catalytic properties than individual Re S₂ or WS₂.This CVD strategy is expected to be extended to the large-scale preparation of other TMDCs and their vertical heterostructures,which is critical for the development of their basic researches and practical applications.(5)The disassembly of 2D vertical heterstructures by CVD.Based on the as-grown Re S₂/WS₂ vertical heterstructures via CVD strategy,we utilized Te as the catalyst to weaken their interlayer van der Waals interactions and then achieved the disassembly of TMDCs vertical heterstructures.Then,in-situ characterizations and theoretical simulations were conducted to elucidate the disassembly mechanism of Re S₂/WS₂ vertical heterstructures.The key factors for the disassembly process was discovered,based on which we found that this kind of disassembly strategy is also applicable to other 2D vertical heterstructures such as WS₂/graphene.This disassembly strategy avoids the damage caused by the common laser irradiation or plasma etching method,and thus is expected to be applied to the editing and erasing of the 2D materials in the devices.