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

Abstract

Hydrogenated amorphous carbon (a-C:H) films were deposited onto glass substrates using low frequency (60Hz) 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–H2 plasma were 2.4–3.1eV and about 108cm−3, respectively. The main optical emission peak of the carbon species observed in the CH4–H2 plasma is shown to be excited carbon CH* at 431nm. The sp3/sp2 ratio, band gap, hydrogen content, and refractive index of a-C:H films gradually increased up to a power of 25W 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.