Intrinsic ultraviolet luminescence from Lu_2O_3, Lu_2SiO_5 and Lu_2SiO_5:Ce~(3+)

摘要

Radioluminescence and thermally stimulated luminescence measurements on Lu_2O_3, Lu_2SiO_5 (LSO) and Lu_2SiO_5:Ce~(3+) (LSO:Ce) reveal the presence of intrinsic ultraviolet luminescence bands. Characteristic emission with maximum at 256 nm occurs in each specimen and is attributed to radiative recombination of self-trapped excitons. Thermal quenching of this band obeys the Mott—Seitz relation yielding quenching energies 24, 38 and 13meV for Lu_2O_3, LSO and LSO:Ce, respectively. A second intrinsic band appears at 315 nm in LSO and LSO:Ce, and at 368 nm in Lu_2O_3. Quenching curves for these bands show an initial increase in peak intensity followed by a decrease. Similarity in spectral peak position and quenching behavior indicate that this band has a common origin in each of the samples and is attributed to radiative recombination of self-trapped holes, in agreement with previous work on similar specimens. Comparison of glow curves and emission spectra show that the lowest temperature glow peaks in each specimen are associated with thermal decay of self-trapped excitons and self-trapped holes. Interplay between the intrinsic defects and extrinsic Ce~(3+) emission in LSO:Ce is strongly indicated.