CORRELATION BETWEEN MICROSTRUCTURE AND THE OPTICAL-PROPERTIES OF TIO2THIN-FILMS PREPARED ON DIFFERENT SUBSTRATES

High refractive index TiO2 thin films have been deposited by electron- beam evaporation on different substrates: Si(111) wafers, thermal SiO2 , fused silica and float glass. Optical properties and growth morpholo gy of the evaporated layers have been characterized by in situ spectro scopic ellipsometry and by transmission electron microscopy. Trajector ies cos Delta = f(tan Psi) and spectroscopic ellipsometry measurements give a coherent description of film growth. The necessity of taking i nto account the presence of a surface layer less dense than the main p art of the film is established. For thicker samples (optical thickness higher than half of the wavelength) index gradients are revealed and evaluated. The columnar structure is found in all samples, but differe nces in column size and-fibre packing are observed on TEM images. The influence of the nature of the substrate on the morphology and then th e optical properties of the films is not well established. (C) 1997 El sevier Science S.A.