A First-principles Study Of The Interaction Of Au With S Group Elements (S,Se) To Form Two-dimensional Nanostructures And Their Related Properties

Nanomaterials have some excellent properties that bulk materials do not have,such as surface and interface effect,small size effect,etc.As one of the nanomaterials,two-dimensional materials have attracted more and more attention because of their extraordinary physical and chemical properties.Graphene is a two-dimensional material.Although it has a very high carrier mobility,it lacks a band gap in the two-dimensional monolayer form,which makes graphene have no advantage in the application of semiconductor switching technology.Although TMD material has ideal band gap and high switching ratio,its carrier mobility is not high enough.Phospholene has good band gap,high carrier mobility and even negative Poisson's ratio out of plane,but its structural instability directly leads to the limitation of its application.Therefore,finding new two-dimensional materials is still an important work at present.In addition,nano-sized gold particles exhibit extremely high chemical activity and catalytic performance compared to gold with very low activity in bulk.At the same time,as a typical semiconductor material,choride has the advantages of wide band gap,high exciton binding energy,easy to form alloys,and is widely used in optical and mechanical devices.In this paper,the interaction between Au and the S group elements(S,Se)has been studied by first principles calculation.Two new two-dimensional semiconductor materials,Au₂S and Au₂Se,have been predicted.It is found that the interaction between Au and the S group elements(S,Se)forms a two-dimensional structure of tetragonal lattice with space group P4/nmm.In terms of the bonding properties,Au and S group elements(S,Se)are ionic bonds,and the Bader charge transfer quantity proves the ionic bond properties.The mechanical and electrical properties of the two materials are also studied.Both of them are direct bandgap semiconductors(the bandgap of Au₂S is 0.19e V,and that of Au₂Se is 0.68e V).By predicting the properties of two-dimensional materials Au2S and Au2Se,it guides the research from theory to experiment,and provides theoretical guidance for the application of two-dimensional materials Au₂S and Au₂Se in semiconductor devices.On the other hand,based on the interaction between Au and S,the self-assembly behavior of sulfur-containing PCB on Au(111)surface was studied.Through STM scanning images and lattice constant measurements,it is found that the PCB molecules are anti-parallel to each other,and the lattice parameters of the PCB molecules match the Au(111)substrate.First-principles calculations show that the self-assembly behavior is influenced by the interaction between the S atom and the Au(111)substrate in the molecule and the interaction between molecules,in which the interaction between the S atom and the Au(111)substrate in the molecule is dominant.The results of this study have a certain guiding significance for the rational design,accurate prediction and controllable construction of molecular nanostructures.