Positron re-emission from epitaxially grown β-SiC

Positron beam experiments have been performed to establish the diffusion behavior and surface branching of positrons implanted with energies varying from 0-25 keV into an epitaxially grown layer of β-SiC on a silicon substrate. The diffusion length of the positrons amounted to 42 nm. The surface branching was as follows: 30% positron emission, 30% positronium formation and 40% trapping at the surface. The energy distribution 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.