SiCxNy thin films were produced by plasma-enhanced chemical vapor deposition and characterized by ellipsometry, Fourier transform infrared and Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, as well as, by near-edge X-ray absorption fine structure measurements in total-reflection X-ray fluorescence geometry. The temperature of synthesis was varied between 100 degrees C and 800 degrees C, the precursors hexamethyldisilazane or hexamethylcyclotrisilazane were used with an addition of N-2, He, and NH3, respectively. The composition of the products was determined to be constant in Si with about 20 at.%, whereas the sum of C and N results in 80 at.% (each varying between 20 and 60 at.%). Consequently, it can be stated, that in the produced silicon carbonitride a network of Si is built with Si-C-Si, Si-C-C-Si, and Si-N-Si bridges. The comparison of the chemical composition and of the physical properties shows for the samples produced with He or N-2, respectively (without NH3) that the refractive index and the absorption coefficient are increasing with an increasing content of carbon in the final formula SiC4-nNn (with n=1, 2, or 3). (C) 2012 Elsevier B.V. All rights reserved.