Red, green, and blue-emitting Li-doped Y 2 O 3 :Re ͑Re = Eu 3+ , Tb 3+ , or Tm 3+ ͒ film phosphors were coated on sapphire substrates using a sol-gel technique in which yttrium nitrate, metal nitrate ͑metal = Eu 3+ , Tb 3+ , or Tm 3+ ͒, lithium carbonate, and citric acid were used as the precursor materials. The effect of annealing temperature on Y 2 O 3 :Re thin films ͑ϳ320 nm͒ and thick films ͑ϳ1.9 m͒ on sapphire substrates was studied with respect to the structural and cathodoluminescence ͑CL͒ properties of the Y 2 O 3 :Re film phosphors. The structural and optical trends observed as a function of annealing temperature differed between the thin and thick films. The Y 2 O 3 :Re ͑Re = Eu 3+ , Tb 3+ , or Tm 3+ ͒ red, green, and blue thick films ͑ϳ1.9 m͒ annealed at 1200°C showed the highest volume and crystallinity of the Y 2 O 3 phase and CL intensity of Li-doped Y 2 O 3 :Re ͑Re = Eu 3+ ,Tb 3+ ,Tm 3+ ͒ red, green, and blue phosphors. These results for thick-film phosphors are discussed on the basis of the optical properties, such as the CL spectrum, color coordinates, brightness, and longevity.Considerable attention has recently been focused on Y 2 O 3 :Re ͑Re = Eu 3+ , Tb 3+ , or Tm 3+ ͒ film phosphors, because they are the well-known red, green, and blue ͑RGB͒ components of oxide RGB triads. 1,2 Film phosphors have also attracted increased interest following reports establishing that carbon nanotubes ͑CNTs͒ are useful as emitters in field emission displays ͑FEDs͒. The contamination of emitter tips by outgassing from powder phosphors is a serious drawback for FED applications. One way of addressing this issue could be to replace powder phosphors with thin-film phosphors. However, despite the advantages of thin-film phosphors, including reduced outgassing, superior adhesion, high image resolution, good heat resistance, and long-term stability, their emission levels are low because of their low internal and extraction quantum efficiencies, 3-6 which suggests that they are not promising candidates for use in FEDs. However, there is evidence that the internal quantum efficiencies of thin-film phosphors are as important for the external quantum efficiency as their extraction efficiencies. Therefore, our recent research efforts have focused on improving both the internal and extraction quantum efficiencies of film phosphors. 3-6 The crystallinity of a thin-film phosphor is strongly correlated with its luminescence efficiency. In general, increases in the deposition temperature, the annealing temperature, and flux addition can be used to improve the crystallinities and luminescence intensities of thin-film phosphors. Increasing the optical volume of thin-film phosphors is another important approach to obtaining maximum brightness. As previously reported, the photoluminescence ͑PL͒ intensity increases with increases in the thickness of the film up to a certain thickness, beyond which the PL intensity is constant. 5 In this study, we focused on the effects of varying the annealing temperature and film thickness on the C...
