Effects of Ge growth rate and growth temperature were investigated on C-mediated formation of Ge quantum dots (QDs) on Si (100) substrate. The samples were prepared by a solid-source molecular beam epitaxy. Ge dots were scaled down and dot density increased with increasing Ge growth rate up to about 2 nm/min, and dot size and density were saturated beyond that. The effect of Ge growth temperature was strong at slow Ge growth rate, while it was insensitive at fast Ge growth rate. Consequently, minimum mean dot diameter of about 25 nm and maximum dot density of about 1.1 x 10(11) cm(-2) were obtained at growth temperature of 450 degrees C. These results suggest that the Ge growth condition of fast growth rate or low growth temperature acts effectively to increase the nucleation probability of Ge adatoms and consequently enables to form Ge QDs by maximizing the effects of C-mediated surface reconstruction. (C) 2016 Elsevier B.V. All rights reserved.