In the present work, a detailed and systematic investigation of diamond films deposited on silicon is realized in an overmoded microwave plasma CVD reactor chamber. It was observed that there is a coupled effect between carbon concentration and substrate temperature on the growth of diamond films. The substrate temperature should be increased with increasing carbon concentration in order to obtain similar surface morphology. And the relative high < 1 1 1 > or < 1 0 0 > orientation diamond films can be obtained when the two parameters are both appropriate. The investigation carried out with 1.5% carbon concentrations further ascertains the rules of the coupled effect. The results indicate that there are five statuses for the surface morphology and the diamond films with < 1 0 0 > and < 1 1 1 > orientation can be deposited at the substrate temperature from around 810 degrees C to 870 degrees C and around 920 degrees C to 960 degrees C, respectively. The quality of the diamond films increases rapidly while the substrate temperature increasing from 750 degrees C to 870 degrees C and keeps relative stable at higher substrate temperature. The experimental results, in some degree, indicate that the diamond films with controllable characters can be deposited in the MPCVD apparatus. (C) 2013 Elsevier B.V. All rights reserved.