Silicon carbon nitride (SiCN) thin films were deposited by plasma-enhanced chemical vapor deposition using hexamethyldisilazane at different nitrogen flow rates. Films were investigated by an atomic force microscope, X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, photoluminescence and nanoindentation. It is established that all the films are amorphous. The deposited films consist mostly of the amorphous SiCx, and SiCxNy networks. To interpret film properties, first-principles molecular dynamics simulations of amorphous SiC, SiCN, SiN and Si3N4 were carried out. Based on the experimental and theoretical results, it is suggested that the photoluminescence peaks at 583-594 nm and 428-490 nm originate from a-SiCx and a-SiCxNy, respectively. An addition of nitrogen to the gas mixture leads to: a reduction of the roughness of the film surface; an enhancement of blue emission; an increase in nanohardness and elastic modulus. (C) 2014 Elsevier B.V. All rights reserved.