On Super Bright Transparent Film Phosphors

Abstract

The film phosphors were prepared by thermal-diffusion reactions between quartz substrate and film materials which are spin-coated. Silicate-based film phosphors (Zn2SiO4:Mn2+ and BaSi2O5:Eu2+) using a quartz (SiO2) substrate and film materials (ZnO:Mn and BaO:Eu) are synthesized in this thesis. Their optical properties were investigated with annealing conditions and dopant (Mn and Eu) concentrations. From X-ray diffraction (XRD) analysis and scanning electron microscope (SEM), we confirmed that film phosphors on substrate were successfully formed and revealed the following characteristics. The Zn2SiO4:Mn2+ film phosphor (thickness = 1μm) became textured along several special hexagonal directions [(113), (223), (333) crystal plane] and their chemical compositions were continuously graded at the interface. The brightest Zn2SiO4:Mn2+ film (Mn/Zn = 5 at.%) showed a photoluminescent brightness as high as 65 % and 40 % compared with a commercial Zn2SiO4: Mn2+ phosphor powder screen at the same weigh excited by 254 nm UV lamp and 147 nm VUV, respectively and it has short decay time of 4.4 ms, and maximum absolute transparency of 70%. The Zn2SiO4:Mn2+ phosphor shell (5 μm) coated on SiO2 powder (100~200 μm) showed a short decay time (τ10% = 7.3 ms) compared to that of a powder phosphor (τ10% = 12 ms) synthesized through a conventional method at same Mn2+ concentration. The BaSi2O5:Eu2+ film phosphor (thickness = 800 nm) revealed some preferred-orientation crystalline [(110), (111), (204) crystal plane]. The BaSi2O5:Eu2+ thin-film phosphor (Eu/Ba = 11 at.%) showed bright green emission and it has a high transparency of 75 %.