Nanohardness and structure of nitrogen implanted Si(x)Al(y) coatings post-implanted with oxygen

“Sialons” have several interesting mechanical, thermal and chemical properties which make them candidates for high temperature applications. Solid solutions in the Si–Al–O–N system were synthesised using nitrogen and oxygen implantation into Si33Al67, Si45Al55 and Si67Al33 thin films deposited by DC magnetron sputtering on glassy carbon substrates. Nitrogen has been implanted firstly at 50 and then at 20 keV, oxygen was post-implanted at 50 keV. The different implantation doses ranged from 1 to 10 × 1017 ions/cm2. High depth resolution profiles were obtained using RBS and resonant nuclear reaction, the chemical bonds were investigated using LEEIXS and these results are correlated to the film structure measured by cross section TEM. The TEM micrographs show a columnar structure perpendicular to the substrate surface in unimplanted coatings. Nevertheless, when nitrogen is implanted grain formation is observed and after oxygen post-implantation gas bubbles appear at the film depth where the maximum oxygen concentration is observed. The correlation of these results with RBS and LEEIXS measurements indicates that nitrogen should be enclosed in these bubbles. Nanohardness was also measured. The highest values are observed in samples post-implanted with 1 × 1017 O/cm2 where nanohardness increases from 3 to 10 Gpa.