Photoconversion and dynamic hole recycling process in anion vacancies in neutron-irradiated MgO crystals

Optical spectroscopy and theory demonstrate that photon excitation of the p ositively charged anion vacancies (F+ centers) at 5.0 eV in neutron-irradia ted MgO crystals releases holes that are subsequently trapped at V-type cen ters, which are cation vacancies charge compensated by impurities, such as Al3+, F-, and OH- 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 w hich the F+ center serves to release a hole to the V-type centers and subse quently trap a hole from an Fe3+ ion. The net effect was the increase of V- type centers mostly at the expense of Fe3+ ions. It was also shown that con currently there was a component which distributed holes directly from Fe3to the V-type centers. [S0163-1829(99)07829-7].