Surface phonons and exciton-polariton coupling in SiC nanocrystals

The paper presents the results of SiC nanocrystal characterization using scanning electron microscopy (SEM), Raman scattering and photoluminescence spectroscopy techniques, as well as X-ray diffraction (XRD). The Raman scattering investigation of porous SiC with different NC sizes have shown new features specific for nano-crystallite materials: appearing of surface phonon modes and the enlargement of diffusing background scattering. Photoluminescence study of PSiC layers with different thicknesses and SiC NC sizes reveals the intensity stimulation for exciton related PL bands. The intensity enhancement for exciton-related PL bands is attributed to exciton recombination rate increasing due to the realization of exciton confinement and exciton-polariton effects in big size SiC NCs of different polytypes (6H-PSiC with inclusions of 15R- and 4H-PSiC). XRD study has confirmed that the investigated porous 6H-SiC layers contain inclusions of 4H-SiC and 15R-SiC polytypes.