Amorphous hydrogenated carbon (a-C:H) thin films deposited on a silicon substrate under various mixtures of methane-hydrogen gas by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MPCVD) was investigated. Microstructure, surface morphology and mechanical characterizations of the a-C:H films were analyzed using Raman spectroscopy, atomic force microscopy (A-FM) and nanoindentation technique, respectively. The results indicated there was an increase of the hydrogen content, the ratio of the D-peak to the G-peak (I-D/I-G) increased but the surface roughness of the films was reduced. Both hardness and Young's modulus increased as the hydrogen content was increased. In addition, the contact stress-strain analysis is reported. The results confirmed that the mechanical properties of the amorphous hydrogenated carbon thin films improved using a higher H-2 content in the source gas. (c) 2005 Elsevier B.V. All rights reserved.