**3.2 Optical investigations of RF sputtered SiC over Si(111)**

The optical behavior of RF sputtered SiC thin film and argon-irradiated SiC samples have been investigated by means of UV–Vis diffuse reflectance spectroscopy. **Figure 3** presents the diffuse reflectance spectra of as-deposited and argon-sputtered SiC thin films at different fluences.

### *Oblique Ar+ Sputtered SiC Thin Films: Structural, Optical, and Electrical Properties DOI: http://dx.doi.org/10.5772/intechopen.112928*

It is clear from **Figure 3** that diffuse reflectance decreases uniformly with increase in wavelength and shows prominent peak near 370 nm indicating the presence of fundamental absorption band in this region for as-deposited thin film. Multiple fringes can be clearly seen for SiC thin film sputtered with argon ion fluence of 5 × 1017 Ar+ cm−2. Surprisingly, for samples sputtered with argon ion fluence of 7 × 1017 Ar+ cm−2, only one broad hump near 280 nm is observed. These diffuse reflectance spectra are converted into corresponding absorption spectra using the Kubelka-Munk theory.

**Figure 4** presents the variation of Kubelka-Munk function as a function of energy for different samples.

Firstly, the square of Kubelka-Munk function was calculated. Thereafter, this quantity is plotted with incident energy. This variation of F(R) with energy as plotted in **Figure 4** is now extrapolated onto the x-axis (energy values). This extrapolation gives the measure of the values of the optical energy gap. The values of optical energy gap for SiC thin film as-deposited and irradiated with varying argon ion fluences are summarized in **Table 2**.

**Table 2** reveals that optical energy gap varies nonlinearly with argon ion fluence. An increase in the optical absorption and a shifting of absorption edge toward longer wavelengths has been observed. The observed behavior is attributed to the different degree of sputtering yield at different argon ion fluences and non-stochiometric sputtering of silicon and carbon.
