We report results of steel substrates coated with hard amorphous carbon and with diamond films. In order to enhance the adherence to the substrate, steel substrates were pretreated by means of a silicon ion beam. Raman spectroscopy was used to analyze the structure of silicon interface while the elastic recoil detection analysis method was applied to determine their composition and thickness. The a-C adherence to the substrate and hardness were also tested. The diamond films were observed by SEM. (C) 2007 Elsevier B.V. All rights reserved.