Identification of Vacancies on each Sublattice of SiC by Coincident Doppler Broadening of the Positron Annihilation Photons after Electron Irradiation

摘要

In the present contribution vacancies on the two sublattices of silicon carbide (6H-SiC) as selectively induced by electron irradiation are specifically identified by coincident Doppler broadening measurements of the positron-electron annihilation photons and by positron lifetime measurements. The vacancies induced by 0.35 MeV electron irradiation are characterized by Si nearest neighbors, as deduced from the increased annihilation probability with Si core electrons. These vacancies are therefore located on the C sublattice. They exibit a positron lifetime of 160 ps as suggested theoretically. In contrast to that, the vacancies by which the positrons are trapped after 2.5 MeV electron irradiation have carbon atoms as nearest neighbors and are, therefore, located on the Si sublattice with a substantially higher positron lifetime of 210 ps.