Hydrogenated amorphous carbon nitride (a-CNx:H) particles and coatings have been prepared in a CH4/N-2, 13.56 MHz radiofrequency discharge. Particles and films have been examined by Scanning Electron Microscopy (SEM) and by infrared (IR) absorption spectroscopy for different nitrogen contents. SEM micrographs show that the dust particles are spherical with diameters in the range 0.2-4 mu m. The surface morphology of the particles is strongly modified with the increase of the nitrogen content in the gas mixture. In the particle and film IR spectra, four predominant absorption bands have been observed. They reveal the presence of C-H, C=C, C=N and/or N-H (1300-1800 cm(-1)), -C equivalent to N and -N equivalent to C (2000-2300 cm(-1)), C-H (2800-3100 cm(-1)) and N-H and/or O-H (3200-3600 cm(-1)) bonds. These absorption bands are studied in order to determine the influence of the nitrogen incorporation. (c) 2004 Elsevier B.V All rights reserved.