**Table 1.**

*Raman deconvolution parameters for varying argon ion fluences.*

peaks of amorphous carbon (a-C) centered at 1373 and 1570 cm−1 characteristic of G peak and D peak have been observed, respectively [19]. Interestingly, one a-C peak at 1469 cm−1 also appears. This symmetric peak can be ascribed to the presence of very small and highly disordered carbon clusters. The Raman parameters, that is, peak positions of G and D peak, FWHM of G peak and D peak and their integrated intensities have been determined from deconvolution procedure. These values have been listed in **Table 1**.

From **Table 1**, it can be seen that the position of G peak lies in the spectral region of 1559–1587 cm−1, which is evidence for mixture of sp2 and sp3 hybridization. In general, decreasing intensity ratio can be interpreted in terms of corresponding increase in sp3 content.

**Table 1** depicts that G peak lies at 1587 cm−1 for as-deposited SiC/Si(111) surfaces. This position of G peak, that is, P(G) moves progressively toward lower wavenumber for SiC surfaces following argon beam exposure at 5 × 1017 Ar+ cm−2. This downshift is attributed to the lowering of C=C vibration modes by the heavier Si atoms in the surface layers. An additional cause of downshifting may be due to higher electronegativity of

carbon atoms directly linked to silicon atoms. This direct linkage subsequently reduced the strength of C=C bonds and hence, absorption with lower frequencies. Along with this, linewidth broadening of G peak is observed with respect to the argon fluence. This clearly reveals the formation of more disordered amorphous structure at this stage of sputtering. Interestingly, intensity ratio of D peak to G peak is 1.98 revealing increase in sp3 content of C-C bonding in the surface layers. Thus, it can be concluded that initial amorphous SiC surfaces are transforming to highly disorder amorphous structure subjected to argon ion irradiation at lowest ion fluence of 5 × 1017 Ar+ cm−2.

With increase in ion fluence from 5 × 1017 to 7 × 1017 Ar+ cm−2, further shift in G peak position toward lower wavenumber has been seen. In contrast to earlier case, we observed less dispersion in the G peak. Moreover, intensity ratio of D peak to G peak decreases drastically. Further, the fraction of amorphous Si increase at this stage of sputtering. Increasing Si content opens up the sp2 sites, thereby creating more sp3 content on the surface.

Hence, Raman measurements reveal that the opening of sp2 sites on a-C results in increased sp3 content in the surface layers. Both FWHM of G peak and I(D)/I(G) ratio decrease with increasing argon fluence.
