Chemical and compositional changes induced by N+ implantation in amorphous SiC films

The effects of 30 keV N+ implantation in amorphous silicon carbide films deposited on silicon substrates by rf sputtering over a fluence range of 1×1016–2×1017 ions cm−2, are studied by means of x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and infrared (IR) absorption techniques. The ion-induced modifications of these films have been investigated on the basis of the chemical state evolution of Si, C, and N (using XPS and AES) and on the basis of the vibrational features of the films components (using IR absorption). The results show that implanted N bonds Si selectively, substituting the C atoms in the silicon carbide, and the C substitution by N results in a composite layer of carbonitrides and free C. An ion-induced C transport has also been observed and correlations are established between the formation of silicon carbonitrides and the dynamical behavior of the C in the implanted layer. The latter appears as a superposition of (a) a chemically induced atomic redistribution, required by local stoichiometry and space-filling possibilities in an amorphous network, and (b) a radiation-induced redistribution, a mechanism that is prevailing at low-fluence implantation.