The effect of deposition temperature, relative humidity of carrier gas and UV-assistance on the growth of Erbium-doped aluminium oxide films has been studied. The films were prepared from aluminium acetylacetonate (Al(C5H7O2)(3)) and erbium (III) Tris(2,2,6,6-tetramethyl-3,5-heptanedionate) (Er(TMHD)(3)) by UV and aerosol-assisted metal-organic chemical vapour deposition, using air with controlled humidity as carrier gas. Amorphous transparent films were deposited between 350 and 460 degrees C. It was observed that UV assistance allows a large decrease down to 5 kJ/mol of the activation energy of the deposition reaction for deposition temperatures lower than 420 degrees C. More over, depositing under high air humidity induced higher deposition rate, lower level of organic contamination and higher film density. Under these conditions Er-doped aluminium oxide films with a refractive index value of 1.71 were obtained at 460 degrees C. (C) 2011 Elsevier B.V. All rights reserved.