Surface and bulk properties of the Filtered Cathodic Vacuum Arc prepared nitrogenated tetrahedral amorphous carbon (ta-C:N) films were characterized by X-ray Photoelectron Spectroscopy (XPS), Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), Raman spectroscopy, Atomic Force microscopy and contact angle techniques.
An increase in the Nitrogen (N) content of the films is accompanied by a reduction in the sp3 fraction, confirmed via the deconvolution of the C 1 s XPS spectra. Critical Raman parameters such as peak position and peak width of the G band, defect ratio, ID/IG and skewness of the G line were analyzed as a function of N content. ToF-SIMS showed the variance of chemical composition with the increase in the sputtering depth.
While some amount of incorporated oxygen and hydrogen were observed for all films; for high N content ta-C:N films signature of CN bonds was evident. Surface energies (both polar and dispersive components) for these ta-C:N films were analyzed in a geometric mean approach. Contact angle measurements using both deionized water and ethylene glycol reveal that upon the insertion of nitrogen into ta-C films, the initial change in the contact angle is sharp, followed by a gradual decrease with subsequent increase in N content.
The variation of contact angle with increasing N content corresponds to an increase of the total surface energy with an increase of the polar component and a decrease of the dispersive component.
MDA Rahman, N Soin, P Maguire, RA D’Sa, SS Roy, CMO Mahony, P Lemoine, R McCann, SK Mitra and JAD McLaughlin.Read Article