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Poly(aryl-ether-ether ketone) (PEEK) films irradiated with 1-MeV and 2-MeV 0+ ions were exposed to positron beams to measure the positron annihilation Doppler broadening as a function of the positron energy. The annihilation lines recorded at relatively low positron energies were found to become broader with increasing irradiation dose, suggesting that positronium (Ps) formation is inhibited in the damaged regions. The positron data were compared with the results of dynamic hardness and electronspin-resonance measurements.The slow-positron Doppler broadening technique is found to be a useful means for damage-depth profiling of Ps-forming polymers.

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Low energy ion beams for surface modification and film deposition AIP Conf. Proc. 576, 911 (2001); 10.1063/1.1395451 Molecular dynamics simulations of low-energy (25-200 eV) argon ion interactions with silicon surfaces: Sputter yields and product formation pathways Capture and loss of valence electrons during low-energy ͑50-500 eV͒ proton scattering from some alkali-halide surfaces such as LiCl, NaCl, and KF have been investigated in comparison with those from the TiO 2 ͑110͒ and Cs-adsorbed Si͑100͒ surfaces. The primary H ϩ ion survives neutralization when scattered from the highly ionized target species existing on the surface. For H Ϫ ion formation, a close atomic encounter with individual target ions is found to be important; the H Ϫ ion is formed more efficiently on the cationic site than on the anionic site despite the fact that the valence electron is spacially localized on the latter. This is because the charge state of scattered hydrogen is determined during a transient chemisorption state and amphoteric hydrogen tends to be coordinated negatively ͑positively͒ on the cationic site ͑the anionic site͒. The final charge state of scattered hydrogen is fixed at a certain bond-breaking distance ͑ϳ5.0 a.u.͒ from the surface where the well-defined atomic orbital of hydrogen evolves. The competing nonlocal resonance tunneling is suppressed at the ionic-compound surfaces due to the existence of a large band gap, so that hydrogen is scattered without losing the memory of such a transient chemisorption state.