Binary Sulfide Controllable Study On Electronic Structure And Optical Properties

ZnS is administered with steady chemical properties,light corrosion resistance,low cost,and pure ZnS can only absorb ultraviolet part of sunlight with wider band gap,as the result in the light of the sun's rays catalytic activity and low efficiency.MoS2 is similar to the graphene layer semiconductor material,due to the quantum confined effect,single MoS2 is different from material with unique optical,electrical properties and exist a bigger application value,however,single MoS2 is a direct band gap of the semiconductor with a 1.8 eV forbidden band width.The band gap of the semiconductor largely affect the light absorption and oxidation reduction ability of the semiconductor.Studies have shown that doping can reduce the band gap,and then extends the absorption band edge to the visible light region.This paper,through the theory of primary research:(I)The doped ZnS with nonmetallic elements,metal elements and effects on electronic structure and optical properties,has achieved as the following results:(1)Studied the effects on ZnS electronic structure and optical properties after doped with metallic elements such as Cu and V.We found that because of the influence of the atomic radius and electronegativity,the lattice constant becomes large and small after doped Zns with VZn,CuZn,The formation energy in CuZn-ZZnS is least in four kinds of single mixed model,at the same time the change betxween distortion,balance structure and system energy is small,can guarantee the stability of structiure.(2)Studied the effects on ZnS electronic structure and optical properties after doped with non-metallic elements,such as F and N.Found that compared with pure ZnS the formation energy of Ns-ZnS can be administered to 5.66 eV indicate that the location of the replacement is not appropriate,show N may be more suitable for clearance.The differences between ZnS doped systems is not very big.in spite of the distortion of the crystal structure and band gap decreases.(3)Studied the effects on ZnS electronic structure and optical properties after codoped with CuZnFS-ZnS ? VZnNs.We discovered the decreases of band gap,as for CuZnNs-ZnS,the N 2p and Cu 3d states appear in the top VB.Thus the VB extends forward to the CB and the Eg is decreased to 1.90 eV,therefore,the absorption edge of CuznNs-ZnS shifts to the longer wavelength region.For the donor-acceptor passivated codoping,Cu 3d orbits would hybridize with S 3p states at the top VB,while F 2s orbits would hybridize with Zn 4s states at the bottom CB in CuznFs-ZnS,? CuZnF The resonance of the defect levels with host phase levels leads to about 32%reduction of the energy gap(1.41 eV vs.2.06 eV),so that the absorption range of the codoped ZnS would extend to visible light region(<492 nm).(?)The doped MoS2 with nonmetallic elements,metal elements and effects on electronic structure and optical properties,has achieved as the following results:(1)Studied the effects on MoS2 electronic structure and optical properties after doped with metallic elements such as Nd.Found that due to the more electronegative of Nd compared to Mo atoms,the change of lattice constant is the largest.The lowest energy in conduction band is uniformly distributed in neighboring 6 Mo atom,and the tallest level in the valence band distribution on 6 Mo and Nd atoms,is conducive to improve the photocatalytic activity.(2)Studied the effects on MoS2 electronic structure and optical properties after doped with non-metallic elements,such as F,Cl,Br and I.It is funny that the lattice constant change is different from the atomic number increases after doped halogen elements.Fs lattice constant decreases because of the wide electronegativity of F,the other three system mainly enhanced with the bigger atomic radius.(3)Studied the effects on MoS2 electronic structure and optical properties after codoped with NdMoFs,NdMoCls,NdMoBrs,? NdMoIs.The band gap of doped systems are all decreased,interestingly,the level just at the CBM in the NbMoFs-1H-MoS2 is fairly flat,whereas that below the Fermi level is much dispersive,as a result,the recombination rate of the electron-hole pairs is low.The top level of VB is rather delocalized around the Nd atom,while the level at the bottom CB,mainly consisted of Mo 4d states mixing with small F 2p oribtals,this further indicates that the larger value of me*/mh*is beneficial for the separation of the photogenerated charge carriers.Most importantly,the electrons in the VBM leap into the two Mo atoms by capturing a photon with enough energy(>1.38 eV).Therefore,the two Mo atoms connected with the dopant F become the active sites during the photocatalytic reaction process.This is,therefore,the first to reveal that the photocatalytic activity of the 1H-MoS2 can be enhanced by the charge compensated codoping.