Weak phonon modes observation using infrared reflectivity for 4H, 6H and 15R polytypes

Infrared reflectivity is investigated as a useful tool for SiC polytype identification. The oscillator parameters (energy, oscillator strength and damping) of the weak folded modes, arising from the folding of the axial optic branch, are determined in the cases of 4H, 6H and 15R polytypes. An example of polytype identification for a sample showing polytype conversion during SiC crystal growth observed in IR spectroscopy is given.