K. Hirata, Y. Kobayashi, S. Hishita, X. Zhao,
Y. Itoh, T. Ohdaira, R. Suzuki, and Y. Ujihira
[Nucl. Instr. and Meth. in Phys. Res. B, Vol.121, pp.267-270, 1997]

The gamma-radiation emitted when positrons are annihilated in a material has a peak whose line width depends upon the Doppler broadening. We have developed an isotope-based, variable-energy positron beam system at the National Institute of Materials and Chemical Research (NIMC) which allows us to use this Doppler broadening technique for depth-selective analysis of damage and defects in near-surface regions. In this paper an outline of our positron beam system which uses ²²Na is given. Its use is described in investigating ion-irradiated amorphous poly(aryl-ether-ether-ketone) (PEEK) and amorphous silicon. The damaged region of Au⁺ bombarded PEEK was found to extend to a greater depth than the average implantation depth for the same material. This is in contrast to the case of O⁺ bombardment. Different widths of annihilation lines observed for as-received and heat-treated samples of amorphous silicon were discussed in relation to structural changes due to annealing.