Nanocrystal formation in annealed a-SiO0.17N0.07:H films

Silicon nanocrystals have been fabricated by annealing amorphous hydrogenated silicon-rich oxynitride (SRON) films in vacuum for 4 h over the temperature range 850–1150 °C. X-ray photoelectron spectroscopy confirmed the composition of the film to be SiO0.17N0.07. Glancing angle x-ray diffraction results revealed consistent silicon crystallite sizes of  nm for films annealed at temperatures , increasing to  nm for films annealed at 1150 °C. The room temperature photoluminescence spectra of the samples annealed at 850 and 950 °C comprised luminescent peaks from silicon nanocrystals and luminescence from the defects in Si–O system. However, only peaks from defects in Si–O system were present in the luminescence spectra from samples annealed at temperatures greater than 950 °C. For the samples annealed at 850 and 950 °C, the presence of strong Si–N bonds prevented the coalescence of smaller silicon crystallites into larger crystallites. Larger, non-luminescent silicon crystallites were only formed in films annealed at temperatures greater than 950 °C, where the energetics of coalescing particles overcame the strong Si–N bonding in SRON films. High-resolution transmission electron microscopy analysis confirmed the presence of silicon nanocrystallites. A proposed growth mechanism of silicon nanocrystals is discussed.