Si quantum dot formation with low-pressure chemical vapor deposition

We report a simple technique for fabricating a layer of isolated Si quantum dots. The procedure uses conventional low-pressure chemical vapor deposition (LPCVD) for an extremely short deposition time in the early stage of poly-Si film growth. The layer resulting from a deposition time of 60 s has isolated Si nanocrystals 5-20 nm in diameter and 2-10 nm in height. Optical absorption measurement shows that the Si-nanocrystal spectrum changes drastically and the onset of absorption shifts to higher energies compared to that of bulk Si. This shift can be explained by the energy gap widening caused by quantum size effects. Special attention is paid to the Brownian migration of Si nanocrystals for fabricating Si quantum dots.