Time-resolved luminescent VUV spectroscopy of F- and F+-centres in single BeO crystals

The time-resolved photoluminescence spectra in the energy region of 2.0-6.0 eV, as well as the excitation spectra (4.0-35.0 eV) and the decay kinetics of luminescence (the time region of 0.2-500 ns) were studied for F- and F-centres in beryllium oxide crystals at T = 10 and 295 K using selective va cuum ultraviolet excitation. The synchrotron radiation from the storage rin g DORIS was used. The aim of the present work was to investigate and compar e the stoichiometric BeO crystals with anion-imperfection samples. F- and F +-centres performed the role a of luminescent probe in a crystal lattice. T he efficiency of energy transfer to F- and F+-centres was investigated on t his basis. The role of the electron-hole and exciton mechanisms of energy t ransfer in BeO crystals and their dependence on temperature were determined . The photoconversion F+ --> F was found using time-resolved spectroscopy m ethods. A comparison of emission properties of F- and F+-centres in BeO and alpha -Al2O3 crystals was made. (C) 2001 Elsevier Science B.V. All rights reserved.