Optical properties of inorganic (ZnO)_100-x(Nd₂O ₃)_x alloy films for the color filter of a plasma display panel

Inorganic (ZnO)_100-x(Nd₂O₃)_x alloy films were prepared at room temperature by the rf-magnetron sputtering, and their optical properties were investigated as functions of the Nd ₂O₃ contents in the films, the film's thickness, and the oxygen content introduced during deposition. These alloy films showed various absorption bands in their optical transmission spectra measured in the visible range. The absorption bands that absorbed light in specific narrow ranges of wavelength could be explained by intra-transitions between the ground-state manifold ⁴I^9/2 and a number of excited states within the 4f shell of the Nd³⁺ ions. The absorptions was also shown to strongly depend on the concentration of Nd³⁺ ion in the film and on the film's thickness. We expect that alloy films with a strong absorption band near 582.5 nm should be effective for filtering orange light emitted from a Ne gas discharge, resulting in the primary color purity of the plasma display panel (PDP) being greatly improved. In particular, we suggest that (ZnO) ₂₀(Nd₂O₃)₈₀ alloy films are the most suitable for color filters of PDPs.