Hot filament chemical vapor deposition (CVD) technique has been used to deposit diamond films on silicon substrate. In the present study, diamond films were grown at various vol.% CH4 in H-2 from 0.5% to 3.5%, at substrate temperature and pressure of 850 degrees C and 80 torr, respectively. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were employed to analyze the properties of deposited films. The formation of methyl radicals as a function of vol.% CH4 not only changes film morphology but also increase film growth rate. At low, intermediate and high vol.% CH4, cluster, faceted cubes and pyramidal features growth, were dominant. By increasing vol.% CH4 from 0.5% to 3.5%, as the growth rate improved from similar to 0.25 mu m/h to similar to 2.0 mu m/h. Raman studies features revealed high purity diamond films at intermediate range of vol.% CH4 and grain density increased by increasing CH4 concentration. The present study represents experimentally surface morphology, growth rate and quality of diamond films grown in hot filament CVD system at various CH4 concentrations. (C) 2011 Elsevier B. V. All rights reserved.