Nitrogenated amorphous carbon (a-CNx) films prepared by unbalanced magnetron sputtering (UBMS) have been investigated and compared with those prepared by conventional magnetron sputtering (CMS). The nitrogen-to-carbon ratio in deposited films increases from 0 to 0.22 as the N-2/Ar gas flow ratio varies from 0 to 8/17. Raman spectroscopy and atomic force microscopy nano-scratch resistance test were used to characterize the a-CNx films. As N content in the film increases, the G peak width decreases from 183 to 170 cm(-1), the I-D/I-G intensity ratio increases from 2.2 to 2.9. The a-CNx films prepared by UBMS show a much lower scratching depth than those prepared by CMS. The pure carbon prepared by UBMS shows the lowest scratching depth, which can be interpreted by the high sp(3) fraction of carbon atoms in the film. (C) 2006 Elsevier B. V. All rights reserved.