Study On Magnetic And Optical Properties Of Rare Earth Elements (Y?Eu) Doped ZnO: First Principle

Zinc oxide(ZnO)is an important semiconductor,with a wide bandgap of 3.37 eV and a large exciton binding energy of 60 meV at room temperature.ZnO has received much attention in a large variety of potential applications including solar cells?photocatalysis and diluted magnetic semiconductor due to its wide set of physical and chemical properties.The rare earth(RE)elements with unique electronic configurations have been paid more attention in the field of semiconductor because of their wide range of optical,electronic,magnetic and photocatalytic characteristics.Recently,a series of lanthanide ions(Y,Eu,etc.)doping ZnO have been extensively studied both experimentally and theoretically,and considerable success has also been achieved in different fields ranging from photocatalysis,solar cells and diluted magnetic semiconductor.In addition,numerous studies indicate that both photocatalytic activity and ferromagnetism of ZnO can be significantly enhanced by doping with RE elements.However,due to the experimental conditions and the differences of the experimental instruments,the opposite experimental results of rare earth elements(Y,Eu)doped ZnO have been found,but there is reasonable theoretical explanation by First principle.Based on the above reasons,rare earth metals(Y,Eu)optical properties and magnetic properties of doped ZnO system was calculated via Materials Studio software CASTEP module based on the density functional theory,the results are as follows:The results show that with the doping amount increasing from 0.0313 to 0.0625,the lattice parameters increases of the doping system,the volume of doping system increases,the higher total energy of the doping system,the higher formation energy of the doping system,thereby making doping difficult of the doping system,as well as lower stability of the doping system.Increased Y-doping concentration weakens the covalent bond,strengthens the ionic bond;Given the increased Y substitutional doping concentration,the Mulliken bond populations and bond lengths of Y-O parallel and vertical to c-axis are decrease for the doping system;Meanwhile,the more Y doping content is,the optical bandgap of the doping system becomes wider,which suggests that the more significant the blue shift of absorption spectra of Y-doped ZnO systems will be.As a result,more difficult doping and lower stability of Eu-mono-doped ZnO systems are observed.Ferromagnetism is mainly attributed to the hybrid coupling effect of Eu 4f and O 2p states and the hybrid coupling effect of O 2p,Zn 3p,and Zn 4s states.The band gaps are 3.01,3.04,and 3.38 eV,and the absorption spectrum is red-shifted for mono-doped systems.A relatively stable antiferromagnetic state is observed along the x-or y-axis bonding of the Eu double-doped ZnO system,whereas a favorable ferromagnetic state is found along the z-axis bonding of the Eu double-doped ZnO system.Ferromagnetism exhibits the characteristics of long-range order,and the maximum energy difference between FM and AFM ordering approximately reaches 105 meV.This finding revealed that the double-doped systems possess high Curie temperature and achieve room temperature ferromagnetism.