Polymer-like hydrogenated amorphous carbon thin films fabricated by plasma-enhanced chemical vapor deposition of cyclohexane precursor

Abstract

Hydrogenated amorphous carbon (a-C:H) films were fabricated by plasma-enhanced chemical vapor deposition (PECVD) of a cyclohexane precursor at ambient temperature at varying deposition pressures from 19.73 to 38.00 Pa and varying plasma powers from 20 to 80 W. The deposition rate of the a-C:H films was strongly dependent on the deposition conditions. The films were all optically transparent with extinction coefficient below 0.0042. The refractive index as an indicator of the film's density varied depending on the deposition conditions. Their surfaces were all hydrophobic regardless of the deposition conditions. The a-C:H films had wide optical bandgaps ranging from 3.09 to 3.69 eV. The refractive index and FTIR spectra were consistent with those of polymer-like a-C:H films. As the deposition pressure decreased and plasma power increased, the intensity of a dominant peak of CHx stretching mode in the FTIR spectra decreased. The relative hydrogen content of the a-C:H films was estimated from an FTIR analysis and determined to have an inverse relationship with refractive index. These results indicated that the formation of more energetic plasmas during deposition at lower pressures and higher plasma powers led to the a-C:H films with reduced hydrogen content and increased density. The observed film properties could be advantageous for several applications, particularly as protective, wear-resistant, low-friction, or anti-reflective coatings for optical windows.