Structural and Photoluminescence Properties of ZnO Thin Films Deposited by Ultrasonic Spray Pyrolysis

Zinc oxide (ZnO) thin films on a silicon (Si) (111) substrate were grown herein using ultrasonic spray yrolysis at 450 °C with different Zn concentrations. The ZnO thin f lms had X-ray diffraction patterns of a polycrysta lline hexagonal wurtzite structure. The (002) and (101) peak intens i ies changed under different Zn concentrations. Fu rthermore, according to Scherer's and Stokes–Wilson equations, the crystallite size and the internal strain of th e ZnO thin films in the (002) and (101) peaks changed with the Zn conce ntration. Optically, the photoluminescence spectra indicated that the ratio of the UV/GB emission of the ZnO thin fil ms was the highest at the Zn concentration of 0.02 mol/mL. We predicted that by increasing the Zn concentrations, the nonradiative transitions, which originated fro m defects, such as lattice and surface defect, become dominant. In con clusion, the ZnO thin films with the Zn concentrati on of 0.02 mol/mL had a better crystalline and optical quality .