Study of structure, tribological properties and growth mechanism of DLC and nitrogen-doped DLC films deposited by electrochemical technique

Diamond-like carbon (DLC) and nitrogen-doped DLC films were deposited on Si (100) substrates by electrolysis of methanol-urea solution under high voltage, at atmospheric pressure and low temperature. The microstructure and morphology of the resulting films were analyzed by means of Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectrometry (FTIR) and atomic force microscopy (AFM). The tribological properties of the films were examined using a ball-on-disk tribometer. As per the results, Raman spectrum, XPS and FTIR measurements suggested the different microstructure between DLC and nitrogen-doped DLC films. The DLC film is consisting of sp2 and sp3 carbon, with the percentage of sp3-bonding carbon to be 55%, while both single and double carbon nitride bonds exist in the nitrogen-doped DLC film, with the N/C ratio of 0.08. The nitrogen-doped DLC film has generally larger surface roughness and better tribological properties compared to the DLC film. Moreover, the related growth mechanism of the resulting films in liquid-phase electrodeposition is discussed as well. Via the reactions of the -CH3 groups with each other to form carbon network and the reactions of the -CH3 and -NH2 groups to form carbon nitride network, respectively, DLC and nitrogen-doped DLC films can be obtained on Si substrates. (C) 2004 Elsevier B.V. All rights reserved.