Erbium-doped yttrium oxide films are prepared from yttrium acetylacetonate (Y(C(5)H(7)O2)(3)) and erbium (III) tris(2,2,6,6-tetramethyl-3,5-heptanedionate) (Er(TMHD)(3)) under standard conditions by UV-aerosol-assisted metal-organic (AA-MOCVD), using air with controlled humidity as the carrier gas. The structure and deposition rate are optimized by studying three experimental parameters; substrate temperature, relative humidity (RH) of the carrier gas, and UV-assistance. Taking all these parameter effects under consideration, the maximum deposition rates are reached under low humidity air and with UV-assistance. Nevertheless, as-deposited Er:Y(2)O(3) films crystallize in the Y(2)O(3) cubic structure and present a very low organic contamination when depositions take place under high air humidity and with UV-assistance. The refractive index of yttrium oxide films under these conditions are relatively high, reaching 1.86 when deposited at 410 degrees C.