Amorphous carbon nitride films have been obtained by pulsed cathodic arc at substrate temperatures of 20, 100, 150 and 200 °C. Film structure was investigated by Fourier Transformed infrared spectroscopy (FTIR) and Raman spectroscopy. Nitrile bands at approximately 2200 cm -1 were identified in all films. As the temperature increased a reduction in the concentration of sp 3 bonds and a decrease in the structure disorder were observed. The relative intensity ratio of Raman D and G bands increased as the substrate temperature increased from 20 to 100°C. Nevertheless, at a critical temperature of 150°C, this trend was broken, and the film became amorphous. A peak at approximately 1610 cm -1 of films grown at 100°C, 150°C and 200 °C suggests that CNx is dominated by a relatively ordered graphite ring like glassy carbon. Moreover, the film grown at 150 °C presented the lowest roughness and the highest hardness and hemocompatibility.