The authors show that by deposition of 0.1 ML of carbon prior to the self-assembled growth of Ge quantum dots on a strained Si1-xGex buffer layer a striking decrease in dot density by two orders of magnitude from about 1011 to 109 cm-2 occurs when the Ge content of the buffer layer increases from 0% to 64%. Their results give experimental evidence for a kinetically limited growth mechanism in which Ge adatom mobility is determined by chemical interactions among C, Si, and Ge. Thus, by adjusting the Ge content of the SiGe buffer layer onto which a carbon submonolayer is deposited they are able to fine tune the density of the carbon-induced Ge quantum dots.