Characterization of non-uniform diamond-like carbon films by spectroscopic ellipsometry

Optical characterization of diamond-like carbon (DLC) films non-uniform in thickness is performed using spectroscopic phase-modulated ellipsometry. This characterization is based on new formulas for the associated ellipsometric parameters of thin films exhibiting a wedge-shaped thickness non-uniformity. These formulas express the associated ellipsometric parameters by means of the density of distribution of local film thickness. The spectral dependences of the optical constants of these non-uniform DLC films are expressed using the dispersion model based on parametrization of density of electronic states. It is shown that this model of the thickness non-uniformity provides a relatively good agreement between the experimental and theoretical data, indicating that the results of the optical characterization of the non-uniform DLC films are close to the correct results. Moreover, it is shown that the model of uniform thin films is unsuitable for the optical characterization of the non-uniform DLC films studied.