| A new type of two-dimensional material,black phosphorus,has received extensive attention from domestic and foreign researchers due to its excellent mechanical,electronic and photoelectric properties since it was successfully prepared in 2014.Black phosphorus is a direct band gap semiconductor whose band gap varies with the number of layers,and whose carrier mobility is quite high.It has wide application prospects in many fields such as novel photoelectric devices,spintronic devices,biomedicine and so on.Despite its excellent performances,black phosphorus has a fatal flaw that is unstable in air and easy to degrade.Therefore,how to enhance the ambient stability of black phosphorus has become the key issue which affects its development.In this work,the DFT calculations were performed using the Vienna Ab-initio Simulation Package(VASP)to investigate the properties of few-layer black phosphorus(bP).The effect of surface modification on the ambient stability of bP,as well as the establishment and application of the evaluation mechanism of charged defects in two-dimensional semiconductor were studied.The main contents of this paper and the results obtained are as follows:(1)We first investigated the adsorption characteristics of various elements across the Periodic Table on few-layer bP.Using the criterion that the ratio of adsorption energy(Eads)and bulk cohesive energy(Ecoh)is greater than one(Eads/Ecoh>1),we selected fifteen elements like Li,Na,K,Rb,Cs,Ca,Sr,Ba,Ni,Tl,La,O,S,F and Cl.We then focused on the effect of the fifteen adatoms on the conduction band minimum(CBM)of bP.It was found that the adsorption of these elements on few-layer bP could significantly shift their conduction band minimum(CBM)downward even below the O2/O2-redox potential,suggesting the possibility of enhancing the ambient stability of few-layer bP.(2)We have also performed a high-throughput computational study by scanning the Periodic Table with an aim of explore the effect of adatoms concentrations on the conduction band minimum(CBM)of monolayer bP.Through the screening of the CBM of the adatom-decorated bP,we summarized which adatoms concentrations can significantly enhance the ambient stability of bP.According to the calculation results,we found that:1)for Be,Mg,Ca,Sr,Ba,Ge,Au and Sc,the adatoms concentrations of 1.54%and above meet the requirement of enhancing the stability of bP;2)for Cs;Y,La,Cl,Fe,Mn and Tc,the adatoms concentrations of 2.04%and above meet the requirement of enhancing the stability of bP;3)for Li,Na,K,Rb,Cu,Ag,Sb,Bi and Ru,the adatoms concentrations of 1.54%and above meet the requirement of enhancing the stability of bP;4)for C,Pb,W and Re,the adatoms concentrations of 5.88%and above meet the requirement of enhancing the stability of bP.In addition,considering a series of problems caused by excessive doping concentration,we believe that Al,Cd,Ga,Hg,Ir,Mo,Ni,Pd,Zn,Pt,Rh,Os,Sn,Tl,N,Si,S,Nb,Ta,O and F are not suitable as adatoms on monolayer bP.(3)The basic reasons why conventional calculation methods of charged defects in three-dimensional semiconductors fail in two-dimensional systems were explored,and an accurate as well as efficient evaluation mechanism was proposed.In the evaluation mechanism,an analytic expression for the asymptotic behavior of charged defects was derived,IE(S,LZ)=IE0 +?/(?)+(?/S)LZ,which was successfully applied to analyze the performances of substitutional defect(O substitution P,OP).In addition,the adsorption characteristics of various elements across the Periodic Table on few-layer bP were also studied,and the electronic density of states of the adatom-decorated bP were presented.According to the specific position of the impurity level in the density of states,whether the impurity level is deep or shallow can be qualitatively judged,which provides a reliable reference for future research. |
PDF Full Text Request