Papier d'Eirini Sarigiannidou en 2019

Raman of Al4C3

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"Al4C3 single crystals are synthesized by the reaction between SiC and aluminum and are structurally verified and analyzed by Raman and X-ray diffraction spectra. The optical absorption measurements of the Al4C3 crystals indicated that the bandgap is about 2.3 eV, which surprisingly is much higher than the bandgap value from the literature. In order to elucidate the discrepancy between the new experimental results and the literature, an advanced ab initio based investigation on the structural, electronic and vibrational properties of the Al4C3 is performed. Remarkably, the scGW approach arrived at an indirect band gap Γ ! L equal to 2.12 eV while the HSE06 calculated band gap was found even closer to the experimental value equal to 2.27 eV. In addition, the hole effective mass is found to be considerably high due to the flat nature of the valence band at the Γ, indicating low hole mobility. Moreover, phonon calculations indicated that the vibrations of the Al atoms contribute mostly on low frequency acoustic branches, while vibrations from C atoms have a stronger contribution to optical phonons."