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

Optical properties of carbon nitride thin films, with and without silicon a ddition, 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), Ra man and Infrared spectroscopy (IR). CN and SiCN films exhibiting predominan tly 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 w e can achieve is about 2.11-2.16 in the visible, comparable with that of pu re diamond like carbon (DLC) film. The index of refraction decreases with i ncreasing nitrogen content in the film, suggesting an increase in the bond polarizability of the material. On the other hand, a significant increase o f the index of refraction is observed with the addition of silicon. (C) 199 9 Elsevier Science S.A. All rights reserved.