Carbon nitride (CNx) thin films were prepared by a hot carbon filament chemical vapor deposition. Several kinds of carbon coils, which are composed of graphite and glassy carbon, were applied as filaments. The carbon coil was heated at about 2073 K in a nitrogen atmosphere of 100 Pa. Effects of the graphite content of the filament on the film microstructure, surface morphology and the nitrogen content in the CNx films Were studied by, using field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS). FE-SEM observations show that the CNx films change from densely columnar to noncolumnar structures with increasing graphite content. AFM observations reveal that the average roughness of the film surface increases with increasing graphite content. It is found from the XPS analysis that the nitrogen content does not depend strongly on the graphite content. The filament with the low graphite content is suitable for preparing CNx films with a dense structure and smooth surface. (C) 2003 American Vacuum Society.