We have synthesized poor quality diamond films, using high methane concentretion, by plasma-assisted chemical vapor deposition on silicon substrates. The roughness and dynamic critical exponents, α and β, of these films have been measured using an atomic force microscope. We show that the morphology, the roughness and the critical exponents of the diamond films are significantly different from those obtained with a low methane concentration. Our results are compared with Kardar–Parisi–Zhang theoretical predictions.