Luminescence of a self-trapped exciton in GeO₂ crystal

The self-trapped exciton (STE) is discovered in the GeO₂ crystal. A PL band at 2.5 eV with a strong Stokes shift is excited only in the fundamental absorption range of GeO₂ crystal with the quantum yield about 0.4 and the decay time constant 800 ± 5 μs at 80 K. The PL thermal quenching occurs at 200 K with the energy about 0.25 eV and the frequency factor 10⁷. At 4.5 K the PL decay kinetics splits into two components with time constants 270 μs and 8000 μs, which can be due to a triplet state split in the zero magnetic field. The STE in GeO₂ is very similar to a STE in SiO₂.