| Since the discovery of graphene,two-dimensional(2D)crystalline materials have attracted extensive attention from scientific researchers due to their unique physical and chemical properties,and have quickly become an important research direction in the fields of materials science,condensed matter physics,and nanotechnology.Owing to their excellent electrical,optical,and optoelectronic properties,2D crystal materials are highly expected.Scientific researchers hope that they can become the material of choice for a new generation of electronics and optoelectronic devices,so as to solve the bottleneck problems encountered in the development of silicon-based materials and meet the requirements of technological development for the performance of various devices and energy consumption.Therefore,optoelectronic devices based on 2D crystals material have become one of the hotspots in this field.The development of new two-dimensional crystal material systems with better properties has always been one of the important directions in the field of 2D crystal research.ReS2,as a new member of the layered transition metal chalcogenide(TMDS)material family,has received extensive attention from researchers.ReS2 is an excellent semiconductor material that can be used in field effect transistors,logic inverters,and photodetectors.Not only that,the low symmetry of the ReS2 structure(triclinic system)makes its many properties exhibit two-dimensional in-plane anisotropy,which can extend its application to the field of polarized photodetectors.However,the previously prepared ReS2 cannot meet the requirements of large-scale device applications due to its uncontrollable thickness and poor crystal quality.This dissertation aims to prepare ReS2 materials for large-scale device applications.First,we develop a space-confined chemical vapor deposition(CVD)growth method to realize the preparation of large-area monolayer ReS2 materials.Further,we analyze the structure and physical properties of ReS2 grown by CVD through in-depth exploration,and discovered its unique multi-domain and grain boundaries(GBs)structure.Then we use "nano-assembled growth" mechanism to reveal the growth process of this multi-domain structure ReS2.Finally,the intrinsic growth behavior of ReS2 on gold substrate was explored,and the controllable preparation of single crystal ReS2 with uniform orientation was realized.Specifically,this dissertation mainly includes the following four parts:1.The controllable preparation of large-area monolayer ReS2 was realized by using the space-confined method.We constructed a micro-reaction chamber using the electrostatic adsorption between mica to limit the growth of ReS2 to the near-surface layer of the mica.Thereby,turbulent flow was transformed into laminar flow,which stabilized the gas-phase mass transfer process of ReS2 growth,and realized the near-steady state growth of ReS2.After applying ReS2 to field-effect transistor devices,the basic electrical and optoelectronic properties were explored.Under illumination conditions,the gate voltage exhibits a significant modulation effect on the photocurrent.When the bias voltage is 0.5 V,the light responsivity of a monolayer ReS2 is about 12 A/W with a light power of 0.05 mW/cm2.2.The grain boundaries(GBs)structure of multi-domain ReS2 was discovered and nano-assembly growth model was proposed.Spherical aberration transmission electron microscope(STEM)was used to characterize the fine GBs structure in ReS2,and it was found that GBs in the multi-domain ReS2 mainly includes two types.One is the seven types of GBs generated by the reconstruction of the Re4-chain during the nucleation stage;the other is the splicing GBs between adjacent sub-domains.The reconstruction of Re4-chain is the main reason for the growth of ReS2 to become polycrystalline domain structure.Therefore,from the micro-atomic scale,we proposed the nano-assembly growth model to explain the formation mechanism of GBs and sub-domains from nucleation to growth of ReS2.This growth mechanism has important guiding significance for understanding the growth mechanism and process of other low-symmetric materials.3.The effects of GBs of different densities on the anisotropic optical and electrical properties of ReS2 were studied,and the thermodynamic and kinetic means to regulate grain boundary density were proposed.Low temperature conditions and higher precursor concentration will result in more GBs in ReS2,as contrast,high temperature conditions and lower precursor concentration will help reduce the GBs density in ReS2.At the same time,theoretical calculations were used as a pioneer to predict the possible properties of different GBs types.For(0,60)? GB,the electronic density of states diagram showed that new electronic states were generated,and in the(120,240)? GB,the generation of new electronic states not only reduced the band gap to 0.53 eV,but also produced ferromagnetism.The ferromagnetism of the material has a wide range of applications in technologies such as sensor information processing and magnetic storage.Therefore,controlling the GBs types in ReS2 and designing and utilizing them are expected to become an effective means to control the properties of polycrystalline ReS2 materials.4.Intrinsic growth behavior of ReS2 on gold substrate and controllable preparation of single crystal ReS2 was realized.Firstly,the effect of annealing treatment on the crystal surface of the gold foil substrate was explored.On the one hand,the annealing process driven by interface energy can improve the surface roughness.On the other hand,the high temperature conditions during annealing can provide enough energy to migrate the grain boundaries in the gold foil.As a result,the crystal lattice was reconstructed to form a thermodynamically and dynamically stable state with low free energy,and a low-index crystal plane with mostly(001)and(101)planes was obtained.Subsequently,the growth behavior of ReS2 on different crystal planes was explored.ReS2 grown on the(001)crystal plane showed two dominant orientations while the ReS2 on Au(101)had only one orientation,meanwhile,its Re4 chain reconstruction was effectively inhibited.Finally,Raman spectroscopy and XPS analysis combined with corresponding theoretical calculations confirmed that there was a strong interaction between Au and ReS2.Therefore,the(101)surface of the gold substrate can effectively inhibit the Re4 chain reconstruction during the growth of ReS2,and make ReS2 exhibit intrinsic growth behavior. |
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