Structural evolution of nanocrystalline silicon studied by high resolution transmission electron microscopy

In this work, nanocrystalline silicon (nc-Si) embedded in amorphous silicon nitride (a-SixNy) films have been characterized by High Resolution Transmission Electron Microscopy (HRTEM). The films have been grown by remote plasma enhanced chemical vapour deposition (RPECVD) onto silicon substrates using a mixture of SiCl₄, NH₃ and H₂. Subsequently, the sample has been introduced to an annealed process. The nanocrystalline inclusions have been measured from the analysis of HRTEM images. The size of nc-Si inclusions is modified due to the annealing process. The diameter of nc-Si inclusions in as-grown films vary from 1.3 to 3.1 nm. In annealed films, a high density of new clusters with reduction of 1 nm of those diameters is observed, as well as the coalescence phenomenon among some nc-Si inclusions is observed too. Consequently, the diameters of annealed films nc-Si inclusions range from 0.7 to 4 nm. The thin films show an excellent photoluminescence emission. The density per unit area and size of the nc-Si inclusions are correlated with the PL emissions. The influence of the structural changes of the nc-Si on the PL emissions is discussed.