Study On The Electronic Structure And Properties Of Graphene-like Two-dimensional Nanomaterials

Material is the symbol of the times,the progress of human society is closely related to the development of materials.Graphene was first prepared through the mechanical stripping method by researchers in 2004,its novel structure and excellent electronic properties make it have good application prospects in many fields,and it has attracted the attention of researchers.However,the inherent bandgap of graphene is zero,lower current switch ratio and smaller spin orbit coupling strength which make it difficult to combine with the modern electronics industry,thereby promoting the researchers' exploration of graphene-like two-dimensional nanomaterials;The electronic structure and properties are the basis of materials,so it is necessary to study them of the graphene-like two-dimensional nanomaterials.Silicene and germanene have better band gap regulation and good compatibility with silicon-based semiconductors to campare with graphene.BN is a typical kind of two-dimensional nanomaterials with the same structure and unique nature of graphene.BN has good stability,thermal conductivity,lubricity and high strength characteristics,so that BN has a good application prospect in nanomaterials.Phosphorene,one of the most popular new two-dimensional nanomaterials,is a natural direct bandgap p-type semiconductor material with large bandgap and higher electron mobility,and its bandgap is easy to control in transistors,so it have a good application prospects in the transistor,solar cells and optical equipment.Therefore,this paper mainly through the modification of silicene,BN,germanene and phosphene(including defects,doping and adsorption,etc.)to study the relevant electronic structure properties.With the perfection of quantum mechanics theory and the maturity of numerical algorithms,the first principle calculations method has a very important position in the research of graphene-like two-dimensional nanomaterials.In this paper,the influence of topological defects(48 defects)on the electronic properties of zigzag and armchair silicene nanoribbons(ZSNRs and ASNRs)were studied by using the first-principles calculations based on density functional theory.We found that 48 defects make ZSNRs and ASNRs show direct and indirect semiconducting properties,respectively.In addition,it was found that ZSNRs were changed from semiconductor properties to metal properties by increasing the defective concentration.At the same time,we studied the electronic structure of the same unit cell of the pristine SNRs and 48 defective SNRs,we found the bandgap of pristine SNRs was opened firstly,then increasing and reducing to zero at last,showing an inverted U-shaped;However,the 48 defective SNRs is directly changed from the semiconductor properties to the metal characteristics when the external electric field is applied.In addition,we studied the effects on the electronic of BN nanoribbon(BNNRs)with C-chain substitution doping.Bandgap variation of BN with increasing number of dopant C-chains was discussed,and found it will undergo the process of insulator-semiconductor-metal properties for ZBNNRs;In contrast,A-BNNRs will experience a transition from the beginning of the insulator properties to the semiconductor properties to metal properties,and finally turn into the semiconductor properties.When the transverse doping of phosphorus in germanene,the nanorbbons maintained the metal properties;When the vertical doping of phosphorus in germanene,its bandgap are opened,all of them showing the direct band gap and the band gap size is 0.128 eV,0.262 eV and 0.284 eV respectively.Ultimately,we studied the basic properties of benzene molecule-adsorbed bilayer phosphorene;They have different stacking methods for the bilayer of phosphorene,and the adsorptions are divided into surface adsorption and interlayer adsorption.Through the calculations we found the adsorption of organic molecules benzene will change the bandgap size of pristine bilayer phosphorene to a certain extent,and the adsorption position(the surface and the interlayer of the bilayer)of the benzene molecule has little effect on its bandgap;The bandgap of AA stacked bilayer phosphorene is about 1.10 eV,AB stacked is about 1.57 eV,while AC stacked is 1.13 eV,this indicates that the bandgap of the bilayer phosphorene is mainly dependent on its own stacking methods.