Defect Structure And Optical Properties Of 2D ZnO Materials

In this article,based on the first-principles calculation,the electronic structure and optical properties have been investigated in 2D ZnO:Mg/Be system with oxygen vacancies and zinc vacancies.The defect structure,magnetism and optical properties have been studied in real earth doping ZnO system.The absorption energy and absorption structure have been discussed about Pt/Au attracted on the ZnO surface.Results show as following:(1)The formation energy of vacancy defects in the two-layer system is lower than that in the single-layer system,indicating that vacancy defects are more likely to exist in the two-layer system.For layered ZnO,the formation energy of oxygen vacancy will decrease with the introduction of Mg atom.The introduction of Be atom is just the opposite,indicating that Be atom has an inhibitory effect on the formation of oxygen vacancy defects.In the single-layer ZnO:Mg/Be system,zinc vacancies are more easily formed than oxygen vacancies.In the 2D ZnO:Mg/Be system,oxygen vacancies will induce impurity levels near the Fermi level to improve the conductivity of the system,while zinc vacancies cannot.Optical absorption spectra have been shown that oxygen vacancy defects cause blue shift,while zinc vacancy defects cause red shift.Therefore,vacancy defects in 2D ZnO:Mg / Be are important defects in improving their conductivity and enhancing their potential applications in photoelectrons and photocatalysis.(2)The lattice parameters of RE doping ZnO structure will be large from which the radius of RE elements is larger than that of Zn.The magnetism of ZnO will change along with RE doping from nonmagnetic to ferromagnetic,which result in orbital hybirdization of4f-orbit of RE,O-2p orbit and Zn-3p and-4s.impurities level will be formed in CBM or VBM when RE elements is doped in ZnO,which will small the band gap and improve the conductivity of materials.In Eu/La/Ce doping ZnO,new absorbing peak will be formed in infrared regions.Along with Eu/Ce-Oi double defects formed in ZnO,interstitial oxygen will obviously change in optical properties.In ZnO:Eu-Oi system,peaks in infrared regions will disappear and form similar peaks to pure ZnO.In ZnO:Ce-Oi system,peaks in infrared regions will blue shift and strengthen.(3)Surface adsorption energy of Pt is significantly lower than that of Au when Pt or Au is absorbed in the surface of ZnO,which indicates that Pt was more easily adsorbed than Au on the surface of ZnO.The Pt or Au adsorbed at the H position is bonded to the adjacent O,but the adsorption energy is the highest at all potential position.The stablest adsorption site of Pt is on the top of the O atom and that of Au is the bridge position.