Optical Properties of ZnFe2O4-SiO2 Granular Films Prepared by Radio-Frequency Magnetron Sputtering

We report on the optical properties of ZnFe2O4-SiO2 granular films prepared on quartz substrates by the radio-frequency magnetron sputtering method. Post-annealing was performed at different temperatures under flow oxygen atmosphere. The morphology and structures of ZnFe2O4 nanoparticles were characterized by x-ray diffraction, transmission electron microscopy and optical absorption spectra. It has been found that there are two different line types in the optical absorption curves of ZnFe2O4-SiO2 granular films. The critical transition of line types occurs when ZnFe2O4 changes from amorphous to crystalline, and the transition temperature increases with the increasing content of ZnFe2O4. There is an obvious blueshift of the optical absorption edge of the granular films with the decreasing annealing temperature.