Determination of the Sickafus index by positron-stimulated secondary electron emission

Measurements are presented of the energy distribution of secondary electrons ejected from copper by an incident positron beam of energy 2 keV. The results show that the energy distribution of the fast secondary electrons is characterised by the form proposed by Sickafus, AE−m, where m ≈ 2. Earlier theoretical calculations and experimental observations suggest that, for incident electron beams of 5 keV and higher, m is closer to unity. By using an incident positron beam the problems associated with the indistinguishability of secondary electrons and low-energy backscattered primary electrons are eliminated, allowing measurements to be taken at low incident projectile energies and a more accurate determination to be made of the Sickafus index m.