Deep understanding the effect of annealing temperature on fluorescence and persistent luminescence properties of Mn doped Zn2GeO4 films deposited by RF magnetron sputtering

Abstract In this work, the effects of annealing temperatures on various properties (i.e., optical properties, surface morphologies and microstructures) of Mn doped Zn-Ge-O films that deposited on the quartz substrate by radio frequency (RF) magnetron sputtering were uncovered. The film without annealing is amorphous and presents a smooth surface as well as good transmittance over 95% in the visible region. Surprisingly, the amorphous Zn-Ge-O gradually transform into Zn2GeO4 crystal with the uprising of annealing temperatures, endowing the annealed films with an intense green fluorescence (534 nm) under 310 nm ultraviolet light excitation and excellent persistent luminescence properties after the excitation. In addition, the nature of the films’ luminescence mechanism was explored. Analysis suggests that higher annealing temperature will increase the crystallinity and grain size of Zn2GeO4, which can effectively affect the formation and increase the number of effective luminescence units, further improving the luminescence intensity. This research provides a crucial admission for improving the luminescence properties of Mn doped Zn2GeO4 films.