Surface tension studies of (Si, N)-containing diamond-like carbon films deposited by hexamethyldisilazane

The (Si, N)-containing diamond-like carbon (DLC) films were deposited using hexamethyldisilazane (HMDSN) reactant in an inductively coupled plasma (ICP) system with the substrate biased by a bipolar-pulsed power supply. Raman spectra of the films were characteristic of a typical DLC film. X-Ray photoelectron spectroscopy (XPS) showed that silicon and nitrogen tended to be bonded to each other. From high-resolution transmission electron microscopy analysis, the diamond-like carbon contains silicon nitride nanoparticles. By measuring the contact angles with the sessile-drop method, the polar and the dispersive components of the surface tension were characterized. The surface tension of the pure DLC (a-C:H) was 26.6 mN/m. By incorporating nitrogen in the DLC film, the surface energy was increased to 33.6 mN/m. The incorporation of nitrogen enhanced the polar share from 8.6 mN/m to 25.6 mN/m, but reduced the dispersive share from 18.1 mN/m to 8.0 mN/m. The polarity of the film was greatly enhanced by the formation of carbon-nitrogen bonds. By further incorporating silicon in the nitrogen doped DLC, the surface tension was reduced back to 24-27 mN/m, close to that of pure DLC films. However, the (Si, N)-containing DLC films had much higher polar shares and lower dispersive shares than those of pure DLC films. Both the effects of the substrate bias and the effects of normal aging on the surface energy of the (Si, N)-containing DLC films were also reported. (C) 2002 Elsevier Science B.V. All rights reserved.