Enhanced luminescence properties of pulsed laser deposited europium activated yttrium oxide thin films.

摘要

The surface roughness of thin film phosphors (TFPs) is one of the factors that affect the brightness of cathodoluminescence (CL). Tailoring the surface roughness of TFPs using various methods can enhance the relatively low brightness of the TFPs. One approach to modifying the surface roughness can be the formation of an anodized silicon surface prior to deposition of TFP. The anodized silicon surface is inherently rough, and thus varying the roughness of the surface can suitably control the roughness of the TFP. This approach has several advantages of lower cost, rapidity and simplicity in wet chemical process.; Another approach to improving the luminescent properties of TFPs can be to insert a buffer layer that is optically favorable for the TFPs and the substrates. In this study, a SiO₂ buffer layer has been investigated to enhance the luminescent brightness. Enhanced luminescence properties were observed from Y₂O₃:Eu films on SiO₂ buffer layered silicon substrates. Due to a smaller refractive index and low absorption characteristics of the buffer layer, a larger amount of total internal reflection in the film and low loss of light intensity during the multiple internal reflections was observed. The light trapped inside the film can escape the film more easily due to a rougher film surface.; A numerical model that was developed from a previous one based on the diffraction scattering theory of light, the steady-state diffusion condition of carriers, and the Kanaya-Okayama's electron beam-solid interaction range satisfactorily explains all the experimental results mentioned above. The model also provides a solid understanding of the cathodoluminescence properties of the TFPs with the effects of other single or multiple luminance parameters. The parameters encountered for the model are surface roughness, buffer layer thickness, electron beam-solid interaction, surface recombination rate of carriers, charge carrier diffusion properties, multiple scattering at the interfaces (air-film, film-buffer layer, buffer layer-substrate, and substrate-air), optical properties of the material, film thickness, and substrate type. The model supplies a general solution in both qualitative and quantitative ways to estimate the luminance properties of the TFPs and it can be utilized to optimize the TFP properties for the application of field emission flat panel displays.