We deposited various metal doped amorphous carbon (a-C:Me) films by radio frequency (RF) magnetron co-sputtering method. Tungsten (W), molybdenum (Mo), and chromium (Cr) were used as the doping metals in a-C film. The applied power on carbon and metal (W, Mo, and Cr) target were 150W and 40W, respectively. a-C:Me films exhibited smooth and uniform surface roughness and the hardness over 15 GPa. Specially, a-C:W film showed the maximum hardness of 18.5 GPa. The coefficient of friction of a-C:W film is relatively lower than that of other films and the critical load value of a-C:W film is higher. These results are related to the concentration of metal in the carbon matrix by the difference of sputtering yield and the change of the structure by the metal bonding. Consequently, W metal is good candidate as the doping metal for the improvement of tribological characteristics. (C) 2012 Elsevier Ltd. All rights reserved.