Dual-Frequency Plasma Enhanced Chemical Vapor Deposition of Diamond-Like Carbon Thin Films

Dual-frequency plasma enhanced chemical vapor deposition was used to grow diamond-like carbon thin films from CH4, H-2 gas mixture. The effects of radio frequency, microwave power, and gas ratio were investigated. Various species have been identified in the CH4-H-2 plasma using optical emission spectroscopy and their effects on film properties have been studied. Increasing the RF power to 400 W, the variation trend of refractive index and CH, C-2 intensity ratios change beyond the 300 W, but the growth rate shows the continuous increasing character from 6 to 11.6 nm/min. Increasing the hydrogen content in the system, the intensity ratio of CH, C-2, CH+ and growth rate show decreasing tendency and the refractive index rises from 1.98 to 2.63. Adding MW produced plasma to the system grows the refractive index to 2.88 and growth rate to 10.8 nm/min. The water contact angle rises from 58.95 degrees to 73.74 degrees as the RF power increases to 300 W but begins to reduce until 400 W. In addition, the contact angle shows a growing tendency by increasing the hydrogen flow to the chamber. In addition, the structures of the films were investigated by the Raman spectroscopy.