Photoluminescence of monoclinic Li3AlF6 crystals under vacuum ultraviolet and soft X-ray excitations

• We have grown monoclinic β-Li3AlF6 crystals.
• We performed XRD-identification and Rietveld refinement of crystal structure.
• We have studied luminescence of monoclinic Li3AlF6 crystals upon VUV and XUV excitation.
• We identified both the intrinsic and defect-related photoluminescence emission bands.
• We estimated electronic structure parameters (Eg≈12.5eV,11.8eV

Using Bridgman technique we have grown monoclinic β-LiAF crystals suitable for optical studies, performed XRD-identification and Rietveld refinement of the crystal structure and carried out a photoluminescence study upon vacuum ultraviolet (VUV) and extreme ultraviolet (XUV)-excitations, using the low-temperature (T = 7.2 K) time-resolved VUV-spectroscopy technique. The intrinsic PL emission band at 340–350 nm has been identified as due to radiative recombination of self-trapped excitons. The electronic structure parameters were determined: bandgap Eg≈12.5Eg≈12.5 eV, energy threshold for creation of unrelaxed excitons 11.8eV13.5Eex>13.5 eV), as well as in the energy range of core transitions at 130 eV. We have revealed UV–VUV PL emission bands at 170 and 208 nm due to defects. A reasonable assumptions about the origin of the UV–VUV bands were discussed.