Mechanical properties of PECVD hydrogenated amorphous carbon coatings via nanoindentation and nanoscratching techniques.

The good combination of chemical and physical properties of hydrogenated amorphous carbon (a-C:H) coatings makes them suitable for tribological, biomedical and microelectronic applications. In this work, nano-indentation and nano-scratching tests have been used to determine the mechanical properties of a-C:H films produced via plasma chemical vapour deposition from CH4-Ar gas mixtures. A capacitive ion-etching reactor has been used for film deposition with a bias and a mixture composition ranging between 0 V and -400 V and 21.4% and 100%, respectively. The variation of Young's modulus (E) and hardness (H) through film thickness has been assessed by continuous multi-cycle indentations, and sub-surface maxima of approximately 150 GPa and 20 GPa have been measured, respectively. A maximum critical load (L-c) for film delamination of approximately 170 mN has been estimated by nano-scratching. A discussion on bias voltage and mixture composition effect on E, H and L-c is presented.