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

Abstract

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.