X-ray spectra and electron densities of states of the complicated semiconductors TlAsS2, Tl3AsS3, Tl3AsS4 and Tl3PS4

Abstract

The complicated as to their composition and crystal structure semiconductors TlAsS2, Tl3AsS3, Tl3AsS4, called briefly TAS, and Tl3PS4 represent a class of compounds promising in the devices of quantum electronics. The electron energy structure of these compounds is investigated both experimentally with x-ray spectroscopy and theoretically by calculations of the local partial electron densities of states (LDOS) and x-ray K-absorption spectra of S and P using FEFF8 code. All theoretical K-absorption spectra and LDOS were calculated ab initio without any adjusting parameters according to the scheme: the self-consistent mt-potentials obtained for the clusters of about 35 atoms were then used in the calculations of the absorption spectra and LDOS for clusters of 87 atoms in the full multiple scattering approximation. The comparison of the calculated K-absorption spectra of S and P of sulfides investigated with their experimental analogues shows that in all cases the theoretical curve reflects good enough the energy positions of all features of the experimental curve. The results of the calculations of LDOS and the experimental emission K- and L2,3-spectra of S and P gave the possibility to determine the energy positions of the electron occupied states of all elements in the semiconductors TAS and Tl3PS4 and to get the information about the hybridization of the electron states in the valence band. The compounds Tl3AsS3 and Tl3AsS4 have the same crystal structure, this leads to the likeness of their K-absorption spectrum of S and the electron energy structure of their valence bands.