Characterization of damage structure in ion implanted SiC using high photon energy synchrotron ellipsometry

Abstract

The optical properties of ion implantation induced disorder in SiC have been investigated in the photon energy range of 5–9eV using spectroscopic ellipsometry (SE). The most characteristic interband transitions of SiC are located between 5 and 8eV. This photon energy region is extremely important for the sensitive characterization of lattice order in SiC. The dielectric function of the disordered layer has been calculated taking into account the surface overlayer consisting of oxide and roughness using complementary characterization tools. The dielectric function of the damaged region has been analyzed using different techniques like second derivative analysis and effective medium approximation (EMA) based on reference dielectric functions. The disorder determined by SE has been verified by Rutherford backscattering spectrometry combined with channelling (RBS/C). Using derivative lineshape analysis combined with simulations, the track size can be estimated. The results can give insight into the effect of the decreasing characteristic size of the unchanged crystalline regions on the optical properties. We created near-surface damage using heavy ions, since the penetration depth of light at photon energies around the direct interband transitions is very small (in the range of 10nm). We used 100-keV Xe at fluences ranging from a slight damage to full amorphization (between 2.0×1013cm−2 and 1.6×1014cm−2).