Si-rich a-SiC:H thin films: Structural and optical transformations during thermal annealing

Amorphous hydrogenated silicon-rich silicon carbide (a-Si0.8C0.2:H) thin films were prepared by plasma enhanced chemical vapour deposition and were thermally annealed in a conventional resistance heated furnace at annealing temperatures up to 1100 oC. The annealing temperatures were varied and the samples were characterised with Auger electron spectroscopy, glancing incidence X-ray diffraction, Raman spectroscopy, Fourier transformed infrared spectroscopy, transmission electron microscopy and photoluminescence (PL) spectroscopy. As-deposited a-Si0.8C0.2:H thin films contain a large amount of hydrogen and are amorphous. When annealing the films, the onset of Si crystallisation appears at 700 oC. For higher annealing temperatures, we observed SiC crystallites in addition to the Si nanocrystals (NCs). The crystallisation of SiC correlates with the occurrence of a strong PL band, which is strongly reduced after hydrogen passivation. Thus PL signal originates from the SiC matrix. Si NCs exhibit no PL yield due to their inhomogeneous size distribution.