First-Principles Study On The Stability,Electronic Structure And Optical Properties Of Er-Doped ZnO

ZnO is one of the most intereting topic in the field of shortwave optoelectronic materials,it is necessary to study the effect of doping on the stability and photoelectric properties of optoelectronic materials.In this paper,the stability and photoelectric properties of ZnO:Erzn and ZnO:(ErZn,NO)doping systems are systematically studied by using the first principle.The main results are as follows,Firstly,ErxZn1-xO(x=0,0.0625,0.1250,0.1875,0.2500)were calculated.The results show that the zinc position is the preferred occupying place for Er.The lattice distortion and the formation enthalpy increase with the increase of Er doping concentration,and then the compound are less stable.The band gap is reduced and it appears irregular variation when the doping concentration reaches 9.375 at.%and 12.500 at.%.When the low concentration(3.125 at.%,6.250 at.%)is doped with Er,the reduced effect on band gap by tension strain is greater than that of the widening effect by doping Er.However this effect is on the contrary when the high concentration(9.375 at.%,12.500 at.%)is doped with Er,the widening effect on band gap by doping Er plays a leading role,so that the band gap is no longer further reduced in this case.With the increase of Er concentration to 9.375 at.%and 12.500 at.%,the electronic transition occurs in the infrared light region with stronger light absorption.After the Er is doped,the transmittance of infrared light and ultraviolet light decreases.With the increase of Er concentration,the reflectivity decreases and absorption increases for visible light.Secondly,the doping systems of pure ZnO,Er single-doped ZnO and Er doped ZnO with intrinsic defects were studied.The results show that only formation energies of Er single-doped ZnO and Er doped ZnO with intrinsic defects systems are negative under the(Zn-poor,Er-rich)environmental conditions.The acceptor-type intrinsic defects introduced by Er-doped ZnO is not donor-type intrinsic defects which usually exists in the undoped ZnO.After the Er atom is incorporated,the impurity energy level formed by the Er-4f electron state is introduced in the energy band,and the Er atom has a strong interaction with the acceptor-type intrinsic defects.As for the optical properties,when the acceptor-type intrinsic defects are introduced into the Er-doped ZnO system,more absorption peaks and two different absorption edges appear on the optical absorption spectrum,and the Er atom interact with the acceptor-type intrinsic defect is one of the important reasons for the light absorption in the visible and infrared regions.Finally,the ZnO:(Erzn,NO)codoped systems were studied.The results show that the effect of N content on the crystal structure of ZnO:(Erzn,NO)codoped system is less than that of Er.The ionization energies of the nErZn-NO complex are deeper than that of the ErZn-mNO complex.ErZn-mNO complex defects are the main compounds which formed during Er-N co-doping ZnO process.With the increase of N concentration in ErZn-mNO complexes doped systems,band gap increases,hybridization of N-2p and Zn-3d is gradually enhanced,the localization degree of Er-4f state is enhanced,and hybridization of Zn-3d and Er-4f state is weakened,so that the valence band is moved in the direction of high energy.The absorption edge of the absorption spectrum appears in different redshift.The corresponding ?i(?)curve of Erzn-mNO(m=2,3,4)has obvious main peak in the infrared region.With the increase of the N concentration,the larger the peak value appears and obvious light absorption phenomenon in the infrared region.