Exciton spectra and energy band structure of CuAlS2 crystals

Three exciton series are investigated in the reflectivity spectra of CuAlS2 crystals at the temperature of 10 K. The nA=1 (ωT=3.543 eV, ωL= 3.546 eV) and nA=2 (3.565 eV) lines of the Г4 (A-series) excitons are observed in the Е‖с polarization. In the Е⊥с polarization, the Г5 excitons (nB=1 at 3.668 eV and nB=2 at 3.686 eV) of the B-series, and nC=1 at 3.813 eV of the C-series are observed. The parameters of the excitons and the more exact values of the Г7 – Г6, Г6 – Г6, and Г7 – Г6 energy gaps are determined. The crystal field and spin–orbit splitting of the valence band is calculated. The electron (mc1⁎) and hole (mV1⁎, mV2⁎, and mV3⁎) effective masses have been estimated.