ANALYSIS OF REFLECTIVITY SPECTRUM AND BAND-STRUCTURE OF BI12GEO20

The fundamental reflectivity spectrum in the energy range 1.5-8.5 eV is reported for Bi12GeO20 (BGO) single crystals. From a Kramers-Kronig analysis the optical constants of BGO are computed. An energy level scheme for interband optical transitions is proposed. A value of 0.7 eV for the spin-orbit splitting of the valence band is suggested. Some features of the band structure are discussed, and the correlations between the band structures of BGO and A2VB3VI-compounds are indicated. The experimental premises for possible simplifications of a theoretical calculation of the band structure are given. © 1979.