IRSL properties of HfO2 obtained by the precipitation method and its correlation to ESR centres

Abstract

Infrared-stimulated luminescence (IRSL) emission and its characterisation are reported for the first time for HfO2 synthesised by the precipitation method and its electron spin resonance (ESR) centres properties are shown in this study. IRSL spectrum has a broad emission band in the blue region, which is centred at about 2.49 eV. A similar emission was observed for the radiofluorescence (RF) with a band centred at 2.52 eV. RF signal intensity decreases with the readout temperature, which might indicate a thermal quenching process.IRSL signal is strongly affected by the readout temperature, as part of its emission is related to the presence of shallow traps (<100 °C). The IRSL shine-down curve is composed of two components with decay times of 15.7 and 800 s, and photoionisation cross-section values of about 1.20 × 10−19 and 2.35 × 10−21 cm2, respectively, based on IRSL carried out at 100 °C after 2 Gy of beta irradiation dose, using a general-order kinetic model. Dosimetric analyses indicated that there is a reproducible signal in IRSL, with a coefficient of variation lower than 9 % for repeatability and 3 % for reproducibility measurements. The dose-response curve has a linear trend in the dose range of 0.3–2.0 Gy. Regarding the photon energy study, it shows an overresponse for photo energy values below 200 keV. Fading of about 40 % after one day of storage was observed.Bleaching measurements indicated that the TL peaks located between 100 and 250 °C share the same trap levels as the IRSL ones. In addition, a possible charge transference is observed from the peak at 330 °C to lower temperature peaks. ESR analyses identified that oxygen vacancies of V+ type in a four-coordinated arrangement are induced by irradiation and are temperature-sensitive. Based on the bleaching and ESR measurements, it is reasonable to infer that V+ type vacancies are likely responsible for the IRSL, and its blue emission.