We present the first comparative study of nucleation and growth of Si quantum dots on SiO2, SiOxNy and Si3N4 substrates using silane Low Pressure Chemical Vapor Deposition at low temperature (570–610°C). The samples are investigated by Atomic Force Micoscopy, Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and Spectroscopic Ellipsometry. We confirm that the chemical nature of the surface and precisely the presence of SiO bonds decreases the Si quantum dot density. By optimising the deposition parameters, a Si dot density of 1012 cm−2 can be obtained below 600°C on a pure Si3N4 surface. The influence of hydrogen, provided by silane decomposition, on the Si nucleation mechanism will be discussed.