Thermoluminescence properties of SrAl2O4:Eu sputtered films with long phosphorescence

SrAl2O4 activated with Eu, one of the long phosphorescent materials with high brightness, was deposited on Si substrates using an RF sputtering technique with facing targets. The as-deposited SrAl2O4:Eu films did not show any peaks in the X-ray diffraction spectra, and the photoluminescence (PL) was not observed. However, the X-ray diffraction peaks were observed after annealing, and a PL peak at about 520 nm was observed after annealing in a reducing H-2 + Ar gas or an inert Ar gas. The composition and morphology of the sputtered films were observed using an energy dispersive spectrometer (EDS) and a scanning electron microscope (SEM). The thermoluminescence (TL) measurements were carried out, and decay times of the phosphorescence and the activation energies were obtained from the peak temperature. TL spectra in higher temperature region which contribute for the long phosphorescence, were examined by the partial heating technique to evaluate the distributed trap depths and the lifetimes. (C) 1999 Elsevier Science B.V. All rights reserved.