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

Abstract

Silicon nanocrystals have been fabricated by annealing amorphous hydrogenatedsilicon-rich oxynitride (SRON) films in vacuum for 4 h over the temperature range850–1150 °C. X-ray photoelectron spectroscopy confirmed the composition of the film to beSiO0.17N0.07. 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 at850 and 950 °C comprised luminescent peaks from silicon nanocrystals and luminescence from the defectsin Si–O system. However, only peaks from defects in Si–O system were present inthe luminescence spectra from samples annealed at temperatures greater than950 °C. For the samplesannealed at 850 and 950 °C, the presence of strong Si–N bonds prevented the coalescence of smallersilicon crystallites into larger crystallites. Larger, non-luminescent siliconcrystallites were only formed in films annealed at temperatures greater than950 °C, where the energetics of coalescing particles overcame the strong Si–N bonding in SRONfilms. High-resolution transmission electron microscopy analysis confirmed the presence ofsilicon nanocrystallites. A proposed growth mechanism of silicon nanocrystals is discussed.