Preparation And Luminescent Properties Of Na-Mg Co-Doped ZnO Thin Films

Zinc oxide(ZnO)is a unique wide band gap semiconductor material.ZnO has an exciton binding energy of up to 60meV and a band gap of 3.37eV at room temperature.Because ZnO has many excellent characteristics,it has broad application prospects in the fields of piezo devices,acousto-optic devices,light-emitting devices,lasers,ultraviolet detectors,etc.Doping in ZnO thin film can improve its photoluminescence properties and double doping has become a research focus at this stage.The sol-gel method was used to prepare ZnO thin film,MgxZn1-xO thin films(x=0.18,0.20,0.22)and NayMg0.2Zn0.8-yO thin films(y=0.01,0.02,0.03,0.04,0.05).SEM and XRD were performed to study the effects of Na+,Mg2+doping concentration and annealing temperature in the range of 350?-500? on the surface morphology and structure of the films.The results show that the grain distribution of Mg0.20Zn0.80O thin film is uniform and the diffraction peak intensity at the(002)plane is 79.93%higher than that of ZnO thin film.The grain size of Na0.02Mg0.2Zn0.78O thin film is uniform and dense and the c-axis is preferentially grown.The diffraction peak strength is 288.28%higher than that of the Mg0.20Zn0.80O thin film.When the annealing temperature is 450?,the surface of the Na0.02Mg0.2Zn0.78O thin film is smoother and the diffraction peak strength is 48.25%higher than that of the unannealed.Then test the transmission spectrum and photoluminescence spectrum of ZnO thin film,MgxZn1-xO thin films(x=0.18,0.20,0.22)and NayMg0.2Zn0.8-yO thin films(y=0.01-0.05).The effects of Na+,Mg2+doping concentration and annealing temperature in the range of 350?-500? on the band gap and photoluminescence of the films were studied.The results show that the band gap of Mg0.20Zn0.80O thin film is 3.59eV,the luminous intensity is 26.89%higher than that of ZnO thin film and the luminescence center is shifted from 379nm to 377nm.The band gap of Na0.02Mg0.2Zn0.78O thin film is 4.19eV,the luminous intensity is 142.57%higher than that of Mg0.20Zn0.80O thin film and the luminescence center is blue-shifted to 370nm.When the annealing temperature is 450?,the band gap of Na0.02Mg0.2Zn0.78O thin film is 4.57eV,which has the strongest absorption capacity for ultraviolet light.The luminous intensity is increased by 134.28%compared with that with the non-annealed state and the emission center is blue-shifted to 359nm.