0000000000485250
AUTHOR
M. A. Monge
Kinetics of nanocavity formation based onF-center aggregation in thermochemically reduced MgO single crystals
Division of Materials Science, Office of Basic Energy Sciences, SC 13, U.S. Department of Energy, Germantown, Maryland 20874-1290~Received 9 February 2001; published 19 July 2001!The dynamics of interacting F centers resulting in F aggregates and nanocavities is modeled in thermo-chemically reduced MgO single crystals. We have recently shown that thermal annealing of thermochemicallyreduced MgO with an exceptionally high F-center concentration (6310
Photoconversion and dynamic hole recycling process in anion vacancies in neutron-irradiated MgO crystals
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.…
Dynamics of F-center annihilation in thermochemically reduced MgO single crystals
Optical absorption measurements were used to monitor the thermal annihilation of oxygen vacancies (F-centers) in thermochemically reduced MgO crystals. The annihilation characteristics were sample-dependent and varied strongly with the F-center concentration. Different mechanisms for the destruction of F centers are suggested depending on their concentration.
Diffusion-controlled annihilation and aggregation of F-centers in thermochemically reduced MgO crystals
Abstract The dynamics of F-center (an oxygen vacancy which has trapped two electrons) aggregation in thermochemically reduced MgO single crystals with an exceptionally high F-center concentration (6×1018 cm−3) is discussed. A theory of the Mg nanocavity formation process is developed based on diffusion-controlled aggregation of elastically interacting F centers and their annihilation at traps. We show that in contrast to the generally accepted viewpoint, the F centers in the bulk are not annealed out at the external sample surface but at internal defects, such as dislocations, subgrain boundaries and impurities. The mutual attraction of the F centers is a key factor controlling the aggregat…