Raman scattering, luminescence, and absorption edge under hydrostatic pressures of layered BiI₃ and SbI₃

Abstract

Abstract Raman scattering from BiI 3 and SbI 3 crystals has been studied at hydrostatic pressures up to 2 GPa. The wavenumbers monotonically increased with pressure for all modes in BiI 3 . Although both crystals belong to the same space group, the pressure coefficients of SbI 3 were significantly different from those of BiI 3 . At pressure P 0 = 0.92 ± 0.01 GPa, the pressure coefficients of all modes changed. Above P 0 , all modes in SbI 3 had positive pressure coefficients as they have in BiI 3 . By comparing this unusual behavior of the Raman lines in SbI 3 around P 0 with the results in BiI 3 and comparing the two lattice structures, we suggest that the type of bonding of SbI 3 changes to become more ionic and hence more similar to the bonding of BiI 3 . This change in structure is supported by changes in the bandwidth of the self‐trapped exciton (STE) luminescence and the slope of the absorption edge photon energy versus pressure. Copyright © 2007 John Wiley & Sons, Ltd.