Structures and optical absorption of Bi2OS2 and LaOBiS2
Abstract The band gaps of isostructural Bi 2 OS 2 and LaOBiS 2 were examined using optical absorption and discussed with the band structures calculated based on the crystal structures determined using synchrotron X ray diffraction. The Bi 6p and S 3p orbitals in the Bi S plane were computationally predicted to constitute the bands near the Fermi level. The optical reflectance spectra of Bi 2 OS 2 and LaOBiS 2 showed optical band gaps of ~1.0 eV, which were close to the computationally calculated direct band gaps of ~0.8 eV. Our results show that Bi 2 OS 2 and LaOBiS 2 are semiconductors containing direct band gaps of 0.8 1.0 eV, and they are suggested to be candidates for optoelectronic materials in the near infrared region without highly toxic elements.