This article deals with the development of a radio frequency plasma enhanced chemical vapor deposition thick film (175 Am thickness) derived from aliphatic chains, trans-2-butene, monomer mixed with hydrogen and various noble gases (helium, argon, and krypton). The main purpose was to engineer an amorphous hydrocarbon film (a-C:H) with low surface roughness of less than 20 nm, designed for use on an "ablator" in a new "MegaJoule" laser facility. Morphology and roughness were characterized by atomic force microscopy. An improvement of 70% is obtained by adding a bias on the substrate.