21. Mainzer Allergie-Workshop

Vacancies and Carbon Impurities in Iron

Point defects in electron-irradiated high-purity α-iron have been studied by positron lifetime measurements. We show that the migration stage of monovacancies occurs already as low as at 220 K, which results in agglomeration of small three-dimensional vacancy clusters. Furthermore, we irradiated carbon-doped iron specimens, where formation of highly asymmetric monovacancycarbon atom pairs was detected during the migration stage of monovacancies at 220 K.

Positrons and electron-irradiation induced defects in the layered semiconductor InSe

The positron annihilation characteristics of the layered semiconductor InSe have been investigated. No evidence for low temperature positron trapping is found in as-grown and heavily deformed InSe. The temperature dependence of the S-parameter in these sample exhibits an increase rate in good agreement with the linear expansion coefficient along the c-axis. The positron lifetime spectra of electron-irradiated 0.01% Sn-doped InSe show a long-lifetime component of 336 ps which is tentatively attributed to positrons trapped at isolated In vacancies. Isochronal annealing experiments performed on these samples show that the recovery of the positron lifetime measured at 77K is accomplished in two…