Dielectric function, electronic properties and optical constants of amorphous carbon and carbon nitride films

The optical and electronic evaluation of amorphous carbon (a-C), tetrahedral carbon (ta-C) and carbon nitride (CNx) films is accomplished by using spectroscopic ellipsometry in the extended energy region from the near IR (NIR) to vacuum ultraviolet (VUV); 1.5 eV up to 9.5 eV, the latter using synchrotron radiation spectroscopic ellipsometry. We demonstrate how the investigation of carbon-based films in the NIR to VUV energy regions can reveal their diamond- or graphite-like character, their chemical bonding and configuration. We present the main criteria based on which the prediction of dielectric function at energy ranges beyond or above the measured range becomes feasible. The similarities and differences between the a-C, ta-C and CNx films resulted from the analyses are ascribed to the electronic structure of the composite carbon-based materials, and they are discussed in view of the carbon bonding and the incorporation of N atoms into the carbon network. (C) 2002 Elsevier Science B.V. All rights reserved.