Ellipsometric study of carbon nitride thin films with and without silicon addition

Optical properties of carbon nitride thin films, with and without silicon addition, grown by magnetron sputtering, have been studied by ellipsometry. The composition, structure and bonding structure of the films were analyzed by Rutherford backscattering (RBS), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Raman and Infrared spectroscopy (IR). CN and SiCN films exhibiting predominantly sp(3) and sp(2) bonding structures with nitrogen content up to 55 at.% can be obtained. It was found that the index of refraction, n, is a strong function of the nitrogen and silicon content. The highest value of n that we can achieve is about 2.11-2.16 in the visible, comparable with that of pure diamond like carbon (DLC) film. The index of refraction decreases with increasing nitrogen content in the film, suggesting an increase in the bond polarizability of the material. On the other hand, a significant increase of the index of refraction is observed with the addition of silicon. (C) 1999 Elsevier Science S.A. All rights reserved.