POSITRON REEMISSION FROM EPITAXIALLY GROWN BETA-SIC

Positron beam experiments have been performed to establish the diffusi on behavior and surface branching of positrons implanted with energies varying from 0-25 keV into an epitaxially grown layer of beta-SiC on a silicon substrate. The diffusion length of the positrons amounted to 42 nm. The surface branching was as follows: 30% positron emission, 3 0% positronium formation and 40% trapping at the surface. The energy d istribution of re-emitted positrons consisted of a narrow contribution centered around 0.5 eV with a wider contribution up to 3 eV. The use of this wide band gap material for field assisted positron moderation is discussed.