Characterization of the boundaries of thin films of TiO2 by atomic force microscopy and optical methods

In this paper slight roughness of the upper boundaries of TiO2 thin films prepared on substrates formed by single-crystal silicon is studied. Atomic force microscopy (AFM) and an optical method based on combining variable-angle spectroscopic ellipsometry and near-normal spectroscopic reflectometry are used for this purpose. It is shown that the values of the basic statistical quantities characterizing this roughness depend quite strongly on the values of the thicknesses of these films (they increase with increasing thickness). Differences observed between the values of the basic statistical parameters determined by AFM and the optical method are explained. It is also shown that the TiO2 films exhibit an inhomogeneity represented by a profile of the complex refractive index. Copyright (C) 2002 John Wiley Sons, Ltd.