First Principles Study Of The S Vacancies Of Bulk ZnS

The defects in semiconductor materials seriously affect the various properties of the material.Zinc sulfide(ZnS)administered as a broadband gap material,since the widely application of the zinc oxide,more and more people begin to pay close attention to the nature of zinc sulfide,zinc oxide and zinc sulfide in the band gap of3.68 eV band gap close to the band gap of 3.44 eV,so zinc sulfide and zinc oxide have similar properties,but must also have differences.Energy problem has always been a hot spot of contemporary scholars,the successful completion of photocatalytic hydrogen production experiment provides us with the possibility of exploring new methods,with the experimental results show that if the zinc sulfide produced after sulphur vacancy will greatly improve its photocatalytic activity,can even hydrogen preparation in visible light,and space is a kind of intrinsic defects of crystal materials.Based on this,this article studies in this field for domestic and foreign research progress and status of this,the sulphur vacancy defects of zinc sulfide in detail first principles calculation,got some can explain the results of the experiment,and the relevant calculating results of zinc oxide were compared.This article is based on density functional theory,using the first principles method discussed the following problems:Firstly,using VASP software,from the wurtzite structure of zinc sulfide,first,the optimization of the lattice constant,it is concluded that using hybrid functional optimization results are more close to the theoretical value.And is able to calculate the zinc sulfide,and then calculate the several common intrinsic defects such as sulphur vacancies,zinc vacancy,sulfur filler,zinc can the formation of the filler,the calculation results show that under the same conditions,the formation of the space has the lowest sulfur can.At the same time,the intrinsic defects in the formation of different concentrations could was analyzed,and found that the lower the sulfur concentration of vacancy defects,the formation energy is larger.,also for the sulfur space under different concentrations of zinc sulfide thermodynamic transition levelwas calculated,the results showed that the concentration,the greater the thermodynamic transition level is smaller.Secondly,this paper focuses on related calculation on the sulphur vacancy.Eigen zinc sulfide in the band gap was calculated first,and the experimental values are compared,PBE calculation results is 2.09 eV,HSE calculation results is 3.25 eV,are smaller than the experimental value,this is caused by limitations of calculation method,does not affect the next step of analysis.Second,we respectively with different concentrations of different charged state of sulphur vacancy for the band and state density calculation,after introducing charged defects,sulfur space surrounding the atomic relaxed for positively charged is when is the outward expansion,inward contraction is not charged.In addition,different charged state,a defect state comes in the middle of the band gap will be the location of the defect will changes over its sulphur vacancy concentration,and affects the band gap is too small.Thirdly,this article separately in the PBE and HSE to sulphur vacancy,comparing the electronic structure calculations for the calculation of charged defects,HSE is superior,because of some defect mode when using PBE calculation can not give the details of his position,often cause disturbance to our analysis.Forthly,The core of this paper is to calculate its effect on the photocatalytic performance of different concentration of S vacancy,through the HSE band calculation,the defect level changes with the vacancy concentration rule,which continue to show that the optical properties of the S vacancy,the vacancy concentration increases,the more prone to optical absorption,and has better photocatalytic activity.