Analysis of carbon nitride films (CNx) deposited by radio frequency (RF) magnetron sputtering on crystalline silicon, under different target self-bias, is reported. Plasma characterisation was performed using mass spectroscopy (MS) and the properties of films were determined in their as deposited state using elastic recoil detection analysis (ERDA), nuclear reaction analysis (NRA), X-ray photoelectron spectroscopy (XPS), infrared absorption, transmission spectroscopy and photothermal deflection spectroscopy (PDS) experiments. A good correlation is observed between the variation of N/C ratio and the growth rate. The resulting changes in the microstructure can be analyzed in terms of surface processes, nitrogen incorporation within the films and the Csp(2) content. (C) 2003 Elsevier Science B.V. All rights reserved.