Surface-polarity-dependent Raman spectra of ultrathin silicon carbide crystal

The surface-polarity-dependent Raman spectra of ultrathin silicon carbide crystal are reported. The relative Raman intensity of the folded-transverse-acoustic phonon to the folded-transverse-optical phonon modes differs drastically between silicon-terminated face (Si-face) and carbon-terminated face (C-face) only for sample thickness below 150 nm. For samples thicker than 150 nm, the relative Raman intensity ratio takes an almost constant value for both Si- and C-faces. These results indicate that the phonon modes confined in the near-surface region are the possible origin of the observed surface-polarity-dependent Raman spectra.