Comparative studies on influence of acetylene to argon flow rate ratios on nano-scratch behavior of a-C:H films produced on steel substrates by plasma immersion ion implantation and deposition

Hydrogenated amorphous carbon (a-C:H) films were fabricated using mixed acetylene and argon plasmas with various flow rate ratios of acetylene to argon. The flow rate ratios (FC2H2 to FAr) have a large impact on the structure of the films. Enhanced film hardness and reduced sp2 content were achieved at larger flow ratios attributable to the high ion flux and efficient etching by hydrogen. However, an excessively high flow rate leads to hydrogen loss from the structure, large stress during deposition, and potential deterioration in the film structure. The appropriate deposition rate is determined based on the scratch behavior of the film.