Electronic properties of undoped LiBaAlF6 single crystals: far-ultraviolet optical, luminescence, and x-ray photoelectron spectroscopy studies

摘要

The electronic structure properties of undoped single crystals of LiBaAlF_6 (LBAF) were determined using lowtemperature (T = 10 K) time-resolved far-ultraviolet (3.7-40 eV) synchrotron radiation spectroscopy, calculations for the spectra of optical functions, and x-ray photoelectron spectroscopy. The bandgap of the investigated compound was found at E_g = 12.3 eV, the energy threshold for creation of the unrelaxed excitons at E_(n=1) = 11.6 eV, and the low-energy fundamental absorption edge at 11.0 eV. The subnanosecond photoluminescence emission band at 6.6 eV in LBAF single crystal is due to radiative valence-core transitions 2p F~- → 5p Ba~(2+).