ELABORATION AND CHARACTERIZATION OF TITANIA COATINGS

The titania coatings have been deposited on polyethylene terephtalate (PET) by r.f. magnetron sputtering in an oxygen-argon plasma from a pu re titanium target. The titania films always consist of a mixture of a morphous and crystallized phases of the anatase structure. The composi tion (O/Ti atomic ratio) established by Rutherford backscattering spec trometry depends on the deposition parameters and mainly on the oxygen partial pressure. The crystallinity, the compactness, the stresses an d the gas barrier effect of the titania coatings increase with the kin etic energy of the sputtered particles. This varies in the same way as the r.f. power and in the opposite manner to the oxygen partial press ure. The refractive index increases all along with the compactness of the titania film; the extinction coefficient decreases and the optical bandgap values increase when the O/Ti atomic ratio increases. Good ad hesion of a titania coating on a PET film needs at the same time activ ation of the surface of the PET by a CO, plasma treatment and optimiza tion of the sputtering parameters.