Character Control Of Monolayer Black Phosphorus Based On The First Principles

As a new layered two-dimensional material,black phosphorus(BP)has many excellent properties including direct band gap,high mobility,high on-off ratio and so on.Compared with multilayer BP,monolayer BP has much higher mobility and larger band gap.Morever,the unique crystal structure of monolayer BP can be controlled by various means.In this thesis,the band structure of monolayer BP under intraplanar strain and the band structure of monolayer BP doped with different impurity atoms were studied.The main research contents are as follows:(1)The effect of intraplanar strain on the band structure of monolayer black phosphorus(BP)has been studied by first-principles methods.The results show that the band gap of monolayer BP has significant changes under different strains.Furthermore,the monolayer BP changes from direct band gap semiconductor to indirect band gap semiconductor under intraplanar uniaxial strain.The monolayer BP keeps direct band gap under the biaxial tensile strain.When the biaxial compression strain increases to 7%,the band gap of monolayer BP will close and the monolayer BP will have metallic properties.(2)The band structure of monolayer BP doped by ⅣA,ⅤA and ⅥA impurity atoms is calculated using the first principles.There is a deformation in the structure of doped monolayer BP.The degree of deformation is related to the radius of the impurity atom.Specifically,if the difference of radius between the impurity atom and the P atom is larger;the structural deformation of the doped monolayer BP will become more obvious.The results show that the number of monolayer BP bands will increase,while the curvature will decrease when monolayer BP is doped.The band gap of the doped system is related to the radius of the impurity atom,it will be larger when the difference of radius between the impurity atom and the P atom is larger.If ⅣA andⅤA atoms are doped,the band gap of monolayer BP will decrease,and if ⅥA atoms are doped the band gap of monolayer BP will increase.In addition,The the results also show that the.The doped systems of O,S,Ge,N and As atoms are direct bandgap semiconductors,while the doped systems of C,Si and Se atoms are indirect bandgap semiconductors.