Since carbon deposition layers in tokamak devices will contain significant amount of tritium, it is important to study its formation mechanism. In this study, tungsten and molybdenum samples with a temperature gradient were irradiated by a mixed ion beam to precisely study temperature dependence of the deposition characteristics. For molybdenum, the temperature of the boundary between "deposition" and "nodeposition" is higher than W. This results roughly agree with the results by the material mixing model proposed by Kriegeretal [K. Krieger. J. Roth. J. of Nucl. Mater. 290-293 (2003) 107.]. Erosion yield of C deposition layer in our experimental conditions was almost equal or less than the yield by Rothmodel [J. Roth, C. Garcia-Rosales, Nucl. Fusion 36 (1996) 1647] for graphite.