First Principles Studies Of Novel Two Dimensional Materials On Substrates

Two-dimensional materials are currently the focus of research in physical chemistry,materials medicine and other fields.They are characterized by thin thickness,high carrier mobility,adjustable band gap width,and exhibit excellent electrical and optical properties.In particular,two-dimensional materials with semiconductor properties can be used as channel materials with high mobility,which has far-reaching significance in the research of reducing the size of transistors and improving the performance of integrated circuits.With the deepening of research,two-dimensional materials family is growing.Theoretically,it is predicted that two-dimensional material has great application potential in integrated circuit,flexible semiconductor,new energy and other fields.The substrate plays a key role in supporting and regulating the properties of two-dimensional materials during their growth.In the experiment,two-dimensional materials can be prepared controllable by selecting appropriate substrates.However,the experimental observation of the microscopic atomic structure of two-dimensional materials is still limited,especially the in-depth study of its intrinsic electronic structure depends on theoretical calculation.In this paper,the atomic structures and properties of several two-dimensional materials have been studied by the method of first principles calculation,and the role of substrate in the growth of two-dimensional materials has been explored.These results provide theoretical support and guidance for the preparation and application of two-dimensional materials.The main content completed is as follows:1.Two dimensional allotrope of boron with large frame structure,called borophyne,which has been proposed for the first time through first-principles calculations.Through structural optimization and binding energy calculation,it is found that the atomic density and binding energy of borophyne are similar to those of borophene.By calculating the band structure,it is found that borophyne has different electronic properties from borophene.β1borophyne has a band gap of 0.75 eV,which is a small band gap semiconductor.The band structure ofβ5 borophyne appears flat band near the fermi surface,and it is predicted that it may produce related insulating states similar to phantom angle graphene.This work not only adds a new member to the boron family,but also provides a valuable reference for the preparation of new boron phase materials.2.The atomic structure and electronic properties of stanene on the substrate were studied by first principles calculation.The distribution of the electronic states of Stanene/Au₂Sn system shows that the tin atoms inside the stanene film are connected by covalent bond with strong force,while the stanene film and the substrate are bound by strong intermolecular bond with weak force,indicating that stannene is expected to be separated from the substrate.By calculating the band structure,it is found that stanene induced by Au₂Sn substrate holds a direct band gap of～0.4 eV at the high symmetric point G,as well as an interesting and important Rashba splitting,which can be applied to spintronic devices.This work investigates the structure and properties of stanene,and the Au₂Sn alloy surface provides a new platform for constructing two-dimensional atomic crystal materials that can be further extended to be integrated into circuits.3.The structure and properties of a two dimensional material on the substrate are studied by first principles calculation.Combined with STM images of SbSn alloy film observed on Cu₂Sb substrate,the atomic configuration of SbSn film was optimized by first principles calculation.By calculating the adsorption energy,it is found that the interfacial interaction between SbSn film and substrate is weak,indicating that the alloy film can be removed from the substrate.By calculating mechanical properties and band structure,it is found that H-SbSn film undergo a transition from indirect to direct band gap semiconductor under lattice strain.By calculating the adsorption energy of oxygen and water molecules,it is found that SbSn film have strong antioxidant and water resistance stability.This work investigated the properties of SbSn film,indicating that the successfully prepared two-dimensional alloy materials（SbSn）may have great potential for device applications under environmental conditions.4.The chiral interfacial system of CO monolayer and Au（111）substrate is studied by first principles calculation based on STM images observed experimentally.The diffusion behavior of CO molecules on the substrate surface was simulated,and it was found that the diffusion barrier of CO molecules decreased linearly with the increase of the electric field,indicating that the electric field can promote the diffusion of CO molecules.The calculation of adsorption energy of CO/Au（111）system shows that with the increase of electric field,the adsorption energy of cluster phase CO molecule decreases,suggesting that its stability has a tendency to decrease,while the increase of homogeneous phase CO molecule adsorption energy means that its relative stability is gradually enhanced,indicating that the electric field can induce the transition between cluster phase and homogeneous phase.This work provides new insights into the asymmetric amplification process of chiral enantiomers and provides a new platform for the study of heterogeneous asymmetric catalytic processes by surface adsorption.In summary,this paper studies the structure,stability and physical properties of two-dimensional materials such as borophyne,stanene and SbSn alloy,as well as the role of substrate in supporting and regulating them.It not only adds a new member to the two-dimensional material family,but also provides a candidate material for the core devices in the current silicon based semiconductor industry.In addition,by combining theoretical experiments,the asymmetric amplification of chiral enantiomers in CO/Au（111）system has been deeply studied,which provides a new insight into the physicochemical origin of chiral properties from the perspective of theoretical simulation of surface adsorption and a new research system for the selective chemical processes of enantiomers.The research in this paper can help us understand the key role of substrate in the growth process of two-dimensional materials,and has theoretical significance for the experimental preparation of new two-dimensional materials and device application.