Spatial separation mechanism in Si quantum dots deposited by chemical vapour deposition on SiO2

A systematic study on the Si inter-dot distance after nucleation on silicon oxide substrates is presented. The process has been followed from the very early stages of the dot formation up to 25% of coverages. Structural characterization has been performed by means of energy filtered transmission electron microscopy, which allowed us to observe dot sizes down to 0.5 nm in radius. Silicon nanodots are shown to be surrounded by a depleted zone, where no new Si dots are observed to nucleate. The average size of such a zone ranges between 4 and 9 nm, depending on the deposition conditions. The dot radius is shown to be proportional to the depleted region size, thus indicating the scaling behaviour of the process.