Improvement of luminescent properties of thin-film phosphors by excimer laser processing

Thin-films of europium doped yttrium oxide, (Y{sub 1{minus}x}Eu{sub x}){sub 2}O{sub 3}, were deposited on sapphire substrates by metallorganic chemical vapor deposition. The films, {approximately} 400 nm thick, were weakly luminescent in the as-deposited condition. A KrF laser was pulsed once on the surface of the films at a fluence level between 0.9--2.3 J/cm{sup 2}. One pulse was sufficient to melt the film, which increased the photoluminescent emission intensity. Melting of a rough surface resulted in smoothing of the surface. The highest energy pulse resulted in a decrease in luminous intensity, presumably due to material removal. Computational modeling of the laser melting and ablation process predicted that a significant fraction of the film is removed by ablation at the highest fluence levels