MOCVD method has been used to grow optical coatings: Sc O is a high index transparent coating while Ta-doped SnO is a transparent conductive oxide. Both films show dense packing and excellent properties. The influence of deposition temperature on the microstructure evolution and optical properties of Sc O films was investigated by X-ray diffraction, scanning electron microscopy and spectrophotometry. Nanocrystalline films were obtained with low transmittance but high refractive index and hardness. Ta-doped SnO films showed sharp change of conductivity with Ta doping, which is attributed to the increase of electron carrier concentration. Improved crystallinity contributes to the improvement in the mobility among doped samples. Microstructural evaluation and property relationships are discussed. © 2002 Elsevier Science B.V. All rights reserved.