In this work, the effects of the dilution of the precursor methane atmosphere by three noble gases (Ar, Ne and He) on the mechanical properties and the microstructure of hydrogenated amorphous carbon films (a-C:H) are presented. The influence of the precursor atmosphere (for Vb=-350 V) and the variation of the self-bias voltage (Vb) are studied. The influence of the substrate temperature also is studied for three temperatures 250 K, 300 K and 420 K for films deposited in atmospheres of 100% CH4 and 2% CH4 + 98% Ar. The films were deposited by Plasma Enhance Chemical Vapor Deposition (PECVD). The mechanical and structural properties were investigated with the use of the nuclear techniques (Rutherford backscattering and elastic recoil detection analysis), infrared and Raman spectroscopies, atomic force microscopy, contact angle measurements, internal stress and hardness measurements. The results shown that the precursor atmosphere dilution by noble gases did not induce substantial modifications in the microstructure or in the mechanical properties of the films. On the other side, the results shown that the composition, the microstructure and the mechanical properties of the films are strongly dependent on the ion bombardment regime. The dependence of the mechanical and structural properties of the films as a function of the substrate temperature was also investigated. Experimental results had been obtained from the film roughness measurements using atomic force microscopy. These results suggest the transition from predominantly adsorption/diffusion mechanisms to the predominance of the ballistic processes in the formation mechanisms of the a- C:H films.