Studies on shallow traps in Li₂B₄O₇:Eu,Mn

Li₂B₄O₇ (LTB) single crystals doped with 0.5 mol% Mn and 0.005 mol% Eu have been grown by the Czochralski method. The presence of Eu³⁺ has been confirmed by photoluminescence spectra of non-irradiated crystals, whereas the presence of Mn²⁺ by absorption spectra of gamma-irradiated ones, as well as by EPR measurements. Unlike in most thermoluminescence studies on pure and doped LTB, performed usually above 300 K, glow curves have been recorded between 10 and 300 K in order to focus the attention on shallow traps. A broad, intense glow peak is observed around 80 K, with three weaker peaks at 205, 255, and 280 K. Based on supplementary T _max - T_stop experiments, the trap parameters have been derived assuming that the glow curve is in fact formed by a superposition of a double Gaussian band related to a quasi-continuous distribution of trapping levels, and several glow peaks produced by discrete traps. The nature of the traps is also discussed.