The deposition, structure and mechanical properties of hydrogenated amorphous carbon films grown in highly Ar-diluted CH4, atmospheres were investigated for a total pressure of 13 Pa. Films were investigated is a function of the self-bias voltage between -50 and -500 V for two extreme CH4 partial pressures, 2 and 100%. For the self-bias voltage that optimizes the diamond-like properties of the films, -350 V, we carried out an investigation as a function of the Ar partial pressure, which ranged from 0 to 99%. The deposition rate and the hydrogen content decreased with progressive Ar dilution, The density and the compressive internal stress are nearly constant. The hardness decreased for Ar-rich precursor atmospheres. The surface roughness was independent of the CH, partial pressure.