Study on the Hydrogenated Diamond-Like Carbon Films Synthesized by RF-PECVD from n-decane

Using a mixture of n-decane and hydrogen, diamond-like carbon thin films (DLCTFs) with high growth rate of 35 nm/min are deposited by radio frequency plasma enhanced chemical vapor deposition. We show that n-decane can be considered as a promising carbon source in DLCTF deposition. The properties of the deposited films such as structure, hydrogen content, deposition rate and refractive index are studied for 20, 50 and 100 sccm hydrogen flow rates (HFRs). It is shown that the deposition rate has a maximum of 35 nm/min for HFR = 20 sccm and by increasing hydrogen concentration, deposition rate drops to 19 nm/min for HFR = 100 sccm. The Raman spectra reveal that the films represent hydrogenated diamond-like carbon features. The photoluminescence background of the Raman spectra is used as a measure for hydrogen content of the films. The hydrogen content varies from 29 to 46% which yields a various amount of sp(3) fraction. The results of the spectroscopic ellipsometry indicate that by increasing HFR, refractive index decreases from 2.1 to 1.9 at 632 nm. The aforementioned trends are attributed to the increase of hydrogen content in DLCTFs which is in very good agreement with enhancing of the photoluminescence background of the Raman spectra.