DUAL-MODE PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION (PECVD) OF POLYMER-LIKE A-C-H FILMS - VIBRATIONAL AND OPTICAL-PROPERTIES

A dual-mode microwave (MW)-radio frequency (RF) plasma reactor has bee n used for the deposition of hydrogenated amorphous carbon (a-C:H) thi n films. Butane is injected and decomposed in the post-discharge of a helium-argon MW plasma, assisted by an RF plasma of variable power (0- 100 W). It has been observed that the energy of the ion bombardment on the substrate, monitored by the RF power, controls the optical proper ties. The dielectric function is parametrized using either a single cl assical oscillator or a three-phase effective medium approximation. Th e deposition rate and the extinction coefficient of a-C:H increase wit h the RF power, indicating an increase of the trigonal sp(2) bonding c onfigurations. Simultaneously, the IR absorption spectroscopy gives ev idence of a decreasing H content and increasing C=CH2 configurations.