Theoretical Study On Electronic Structures And Optical Properties Of Doped MoS₂

In recent years, the emergence of analogous graphene has attracted wide attention. In this paper, we use MoS₂ as the research object,based on first-principles density functional theory by Materials Studio software to calculate and analyze the influence of the stability,the electronic structure and optical properties,by replace S doped,replace Mo doped,adsorption Co ? V atomic and doped Cr atomic between MoS₂- WSe₂ heterojunction layers?vacany defect and complex defects. In the last of this paper,we summarized what we has done and provided some prospects for the following work.Get the following conclusions:?1? Through the first main group of V of the non-metallic elements substitutional doping MoS₂.It is found that the change of the volume is related to the atomic radius. In general,the larger the radius of the doped atoms, the larger the volume of the doped system;calculated results show that the introduction of the first main group of V of the non-metallic impurity decreases the band gap,by calculating the formation energies,we know that stable N- MoS₂ system has the highest stability.By analyzing the density of states,we found at the Fermi level has a peak density of states, indicating that there are impurities energy band gap in band gap;at the same time the optical properties also changed : at 1.3 e V-1.73 e V and 1.86 e V-3.26 e V appears of two absorption peaks in the infrared region and near the visible region, indicating that this area's conductivity has been enhanced, absorption spectra and reflection spectra have decreased, indicating that doping has high transmittance.?2? By computing the properties of MoS₂ substituted by Ta,W,Re for Mo, we find the W-doped properties has changed little and most stable nature; the three doped atoms around with the S atoms are formed a covalent bond, the analysis is due to the electric of the three dopant atoms and S negative difference of less than 1.7e V caused; dielectric functions and absorption spectra peak to the direction of the low energy shift and peak shape changes,peak intensity is significantly decreased, indicating that the conductivity doping system is weakened, the energy region near visible and ultraviolet region of light transmittance higher than the intrinsic system. Then calculate the single-layer MoS₂ surface adsorption of Co, V electrical and magnetic properties of atoms, the results show that the adsorption position on the Mo atom is the most stable, and absorbed Co, V atoms respectively with S atoms are formed a covalent bond, crystal structure has changed; Co and V respectively doped MoS₂ with the magnetic moment is 2.45?B and 1.62?B, analyzing that doping system introduced impurity band obtained mainly form impurity atom and S atoms.?3? After the atom Cr doped MoS₂-WSe₂ system in the layer, the Cr atom with the surrounding S and Se atoms formed a covalent bond of relationship, and the incorporation of the system was changed to metal; impact on their optical properties, compared to the previous several systems, left blue shift, the peak has also been reduced, from the absorption spectrum and the energy loss spectroscopy can be seen, although the addition of impurity Cr weak the absorption of ultraviolet light, but increases the absorption intensity of infrared light and visible light.?4? At the end of the study, we have studied the effects of the complex defects with vacancies and Cr atoms for the doping of Mo atoms and vacancies formation of MoS₂ found in the vicinity of these defects undergone significant lattice distortion, the band gap is significantly reduced, and from vacancy complex defects formed at a position closer to more easily formed. Single Mo vacancy defects and complex defects of MoS₂ have a greater impact on the gap of MoS₂, both are introduced defects or impurity levels. It is found that the two kinds of composite defects do not produce the magnetic properties of the system.