Effects of applied power on hydrogenated amorphous carbon (a-C:H) film deposition by low frequency (60 Hz) plasma-enhanced chemical vapor deposition (PECVD)

Hydrogenated amorphous carbon (a-C:H) films were deposited onto glass substrates using low frequency (60 Hz) plasma-enhanced chemical vapor deposition and the effects of the applied power on a-C:H films deposition were investigated. During deposition, the electron temperature and the density of CH4-H-2 plasma were 2.4-3.1 eV and about 10(8) cm(-3), respectively. The main optical emission peak of the carbon species observed in the CH4-H-2 plasma is shown to be excited carbon CH* at 431 nm. The sp(3)/sp(2) ratio, band gap, hydrogen content, and refractive index of a-C:H films gradually increased up to a power of 25 W and then saturated at higher power. This tendency is similar to the variation of plasma parameters with varying applied power, thereby indicating that a strong relationship exists between the properties of the films and the plasma discharge. (C) 2012 Elsevier Ltd. All rights reserved.