|
Thin film phosphors are inferior to powders in luminescent intensity and efficiency due to the inner reflection and the loss of light. Nevertheless, they have been widely studied for the applications of flat panel displays, because they have advantages of thin layers, high pixel, high contrast, easy integration, and chemical stability, etc. It has been known that surface modification, which means rougher surface, is one of the methods for the enhancement of the luminescent intensity. In this work, we investigated the effects of substrates and rf powers on surface modification of thin film phosphors, ZnGa2O4:Mn (green), CaTiO3:Pr (red), YAG:Ce (yellow), and ZnO:Er (infrared). Photoluminescence (PL) and cathodeluminescence (CL) spectra of thin film phosphors deposited on sapphire substrates exhibited much higher luminescent intensity than those deposited on glass substrates, because the former had rough surface that allowed surface light scattering, leading to higher PL and CL. Another method was to insert preferred oriented ZnO buffer layers between thin film phosphors and glass substrates. Rf power was also an effective way to modify the surface. Higher rf power could cause rougher surface of thin films due to high energetic ion bombardments, but excess high rf power inversely deteriorated the surface resulting in lower PL and CL. |