0000000000335703
AUTHOR
R. Pareja
showing 4 related works from this author
Optical absorption and Raman studies of neutron-irradiated Gd3Ga5O12 single crystals
2018
Abstract In this work we have performed a comparative analysis of optical absorption and micro-Raman spectra for series of Gd3Ga5O12 (GGG) single crystals irradiated by fast neutrons with fluences from 1016 n/cm2 to 1018 n/cm2. It was found that the optical absorption spectra of non-irradiated Czochralski grown GGG consist of the relatively narrow lines in the UV spectral range related to the 4f–4f transitions in Gd3+. Transitions from the 6S7/2 ground state to the 6P, 6J and 6D states in a Gd3+ cation are clearly detected. For a GGG crystal containing Ca impurity ions, additional absorption band at 350 nm is observed, and it is tentatively ascribed to oxygen vacancies associated with Ca im…
Photoconversion and dynamic hole recycling process in anion vacancies in neutron-irradiated MgO crystals
1999
Optical spectroscopy and theory demonstrate that photon excitation of the positively charged anion vacancies (F{sup +} centers) at 5.0 eV in neutron-irradiated MgO crystals releases holes that are subsequently trapped at {ital V}-type centers, which are cation vacancies charge compensated by impurities, such as Al{sup 3+}, F{sup {minus}}, and OH{sup {minus}} ions. The concentration of trapped-hole centers was found to exceed that of available anion vacancies. The disproportionately large amount of holes produced is attributed to a dynamic recycling process, by which the F{sup +} center serves to release a hole to the {ital V}-type centers and subsequently trap a hole from an Fe{sup 3+} ion.…
Positrons and electron-irradiation induced defects in the layered semiconductor InSe
1992
The positron annihilation characteristics of the layered semiconductor InSe have been investigated. No evidence for low temperature positron trapping is found in as-grown and heavily deformed InSe. The temperature dependence of the S-parameter in these sample exhibits an increase rate in good agreement with the linear expansion coefficient along the c-axis. The positron lifetime spectra of electron-irradiated 0.01% Sn-doped InSe show a long-lifetime component of 336 ps which is tentatively attributed to positrons trapped at isolated In vacancies. Isochronal annealing experiments performed on these samples show that the recovery of the positron lifetime measured at 77K is accomplished in two…
Creation and thermal annealing of structural defects in neutron-irradiated MgAl 2 O 4 single crystals
2018
Abstract Several novel hole-type defects (a hole localized at a regular oxygen ion near a negatively charged structural defect) have been revealed in fast neutron irradiated MgAl2O4 crystals using the EPR method. The pulse annealing of the EPR signal of these centers was compared to that of radiation induced optical absorption in the same crystals. Taking into account the determined models of V1, V2 and V22 paramagnetic centers, the tentative scenario of the thermal annealing process of neutron-induced defects (hole-type and complementary electron F-type ones) is proposed. In addition, one more paramagnetic hole center consisting of an Al|Mg as-grown antisite defect near an aluminum vacancy…