Structural characterization of amorphous SiCxNy chemical vapor deposited coatings
Résumé
Chemical bonding and local order around the different atoms of thick amorphous SiCxNy deposits [0.03⩽x/(x+y)⩽0.67] prepared with chemical vapor deposition at 1000–1200 °C using TMS–NH3–H2 have been investigated using x-ray photoelectron spectroscopy (XPS), Raman spectrometry, Fourier transform infrared spectrometry (FT-IR), electron energy loss spectroscopy (EELS) and 29Si magic-angle spinning nuclear magnetic resonance spectrometry (MAS-NMR). XPS analyses have shown that the main bonds are Si–C, Si–N, and C–C, and have suggested the existence of C–N bonds. According to Raman analyses and complementary FT-IR absorption of thin films, the coatings are nonhydrogenated. Si, C and N atomic chemical environments are more complicated than in a mixture of pure Si3N4–SiC phases. The examination of the Si KL2,3L2,3 line shapes recorded by XPS have allowed one to state the existence of Si(C4−nNn) units. Mixed coordination shells around silicon have been confirmed by EELS analyses. Additionally, FT-IR reflection analyses have proved that Si is both bonded with N and C. Indirect indication has been obtained owing to the 29Si MAS-NMR analyses of powders. Raman analyses have been conclusive to assume that C–C bonds correspond to a mixed sp3−sp2 carbon configuration linked with Si(C4−nNn) tetrahedra with 0⩽n⩽4.