Effects of electron beam current density and temperature on peak height ratios D-5(j)/D-5(0) for cathodoluminescence of Ln(2)O(2)S : Eu3+

Abstract

The change in the initial and steady state (similar to 0 and 5 s after initiation of electron beam irradiation) peak heights from the D-5(2) double right arrow F-7(3), D-5(1) double right arrow F-7(3) and D-5(0) double right arrow F-7(2) cathodoluminescent transitions from Eu3+ have been studied for Ln(2)O(2)S:Eu3+ (Ln = La, Gd) phosphors. Specifically, the intensity ratio of these transitions, designated as D-5(1)/D-5(0), increased and then decreased for both La2O2S:Eu3+ (0.1 mole%) and Gd2O2S:Eu3+ (0.4mole%), as the current density was changed from 10 towards a 1000 mu A/cm(2). These effects were shown to be consistent with feeding from the higher D-5(2) excited state to the lower energy D-5(1) excited state, resulting in an increase of the D-5(1)/D-5(0) ratio at low current densities. At higher current densities, energy was funneled from the D-5(1)-D-5(0) states, resulting in a decrease of the D-5(1)/D-5(0) ratio. These effects of feeding versus funneling were dependent on both the Eu3+ concentration and current density, and changed with time (i.e., approached a steady state after similar to 5 s) due to increased activator interactions from induced internal electric fields. The magnitude of thermal quenching versus interaction quenching was investigated using changes of the peak height ratios of D-5(2)/D-5(0) and D-5(1)/D-5(0). (c) 2006 Elsevier B.V. All rights reserved.