Positron annihilation study of vacancies in type IIa diamonds illuminated with monochromatic light

Electron irradiated type IIa diamonds were investigated by positron lifetim e and Doppler broadening spectroscopies during illumination in the photon e nergy range 2.2-3.5 eV. Illumination caused neutral vacancies to become neg atively charged, and at photon energies close to 2.85 eV the charging was m ost effective. This suggests that the electronic level for the negatively c harged monovacancy is situated 2.85 eV above the valence band. The photon f lux dependency of the charging at the photon energy of 2.83 eV depends stro ngly on temperature and is attributed to recombination between holes and ne gatively charged monovacancies. (C) 2001 Elsevier Science B.V. All rights r eserved.