Trapping states and excited state ionization of the Ce3+ activator in the SrHfO3 host

Abstract

a b s t r a c tWe study trapping states of Ce 3+ -doped SrHfO 3 by thermally stimulated luminescence in a wide temperature range (10-730 K). We determine characteristic parameters of the traps by the initial rise technique. We also determine the energy of thermal ionization of the excited state of Ce 3+ in SrHfO 3 host by purely optical method based on the study of UV illumination-induced thermoluminescence. The method provides a value of the thermal ionization energy of about 0.25 eV.

Delayed recombination and excited state ionization of the Ce3+ activator in the SrHfO3 host

“…Those traps might be rather distant from the Ce 3+ center and therefore have a negligible effect on the delayed recombination signal. The best fit of delayed recombination data provides an ionization energy value 0.25 ± 0.02 eV, consistent with that found from the TSL study [6]. The uncertainty 0.02 eV corresponds to the range of E ion within which a satisfactory fit is obtained.…”

“…(3), namely the trap depths E and frequency factors s (related to detrapping times), were determined from an independent experiment using the TSL technique [6]. Their values corresponding to traps associated with the TSL peaks observed in [6] are reported in Table 1. The detrapping time is expected to have the form…”

“…The host excitation, instead of the excitation into the 4f-5d 1 absorption band of Ce 3+ , was chosen due to the fact, that PL intensity under host excitation (200 nm) is less affected by experimental distortions connected with the powder form of the sample (detailed explanation is given in [6]). The dashed line represents our assumption (see [6]) that the Ce 3+ emission below RT is constant. The curve was used to correct the delayed recombination data (below) for the temperature quenching of the Ce 3+ emission.…”

“…The experimental data (solid circles) were measured in [6] under host lattice excitation at 200 nm. The host excitation, instead of the excitation into the 4f-5d 1 absorption band of Ce 3+ , was chosen due to the fact, that PL intensity under host excitation (200 nm) is less affected by experimental distortions connected with the powder form of the sample (detailed explanation is given in [6]). The dashed line represents our assumption (see [6]) that the Ce 3+ emission below RT is constant.…”

“…Recently, the value 0.25 eV for the ionization energy was determined [6] by a TSL study of SHO:Ce microcrystalline powder after UV illumination.…”