Positron annihilation study on surface structure of biological samples implanted by ions with low energy

The organic materials of biological samples, such as lima bean and peanut, were implanted respectively by nitrogen ions with an energy of 100 keV and vanadium ions with an energy of 200 keV. The positron annihilation lifetime spectra of implanted and non-implanted samples were compared with each oth er especially in tau (3) and I-3. The experimental results showed that befo re implantation there were many small holes with diameters of 0.48 and 0.7 nm in lima bean and peanut, respectively. After ion implantation, the size of holes would be changed because of organism cross-linking and scission, T he effective penetration range of implantation of ions with low energy into biological samples is about 200 mum.