Comparative study of silicon quantum dot formation In - situ grown with a gas mixture of SiH₄+N₂ and SiH₄+NH₃

In this study, we investigated the growth mechanism of silicon quantum dots (Si QDs) embedded in a Si-nitride film formed by using plasma-enhanced chemical vapor deposition. Special attention was paid to the influence of the nitrogen source, especially in molecular nitrogen (N₂) and ammonia (NH₃). We found that the nitrogen source played a decisive role in determining the location of nucleation sites of Si QDs. In the case of the SiH₄+NH₃ gas source, the Si QDs mainly nucleated at the surface of the Si substrate, in contrast to the case of SiH₄+N₂ which should no such tendency. We believe that a specific surface reaction of the initially adsorbed NH₃ molecules forming lowdimensional structures (NH₂-Si-Si-H) on the Si substrate provide the nucleation sites for Si QDs when using a SiH₄+NH₃ plasma.