We present a study of the influence of H-2 as a carrier gas on the nucleation and growth of silicon quantum dots (Si-QDs) on SiO2 by chemical vapor deposition (CVD). Compared to deposition from pure SiH4, the dilution of SiH4 in H-2 leads to a strong decrease of the nucleation/growth rate, with the same Si-QDs morphology however. The effects of doping gas, phosphine and diborane, on Si-QDs nucleation and growth were also investigated. Silanol groups at the SiO2 surface were identified as nucleation sites for Si-QDs. We study the influence of H-2 and doping gases on their activity toward Si-QDs nucleation. (C) 2003 Elsevier Science B.V. All rights reserved.