Low-temperature positron annihilation study of B+-ion implanted PMMA

Temperature dependent positron annihilation lifetime spectroscopy (PALS) measurements in the range of 50-300 K are carried out to study positronium formation in 40 keV B+-ion implanted polymethylmethacrylate(B:PMMA) with two ion doses of 3.13·1015 and 3.75·10 16 ions/cm2. The investigated samples show the varioustemperature trends of ortho-positronium (o-Ps) lifetime τ3 and intensity I3 in PMMA before and after ion im-plantation. Two transitions in the vicinity of ̃150 and ̃250 K, ascribed to γ and β transitions, respectively, are observed in the PMMA and B:PMMA samples in consistent with reference data for pristine sample. The ob-tained results are compared with room temperature PALS study of PMMA with different molecular weight (Mw) which known from literature. It is found that B+-ion implantation leads to decreasing Mw in PMMA at lower iondose. At higher ion dose the local destruction of polymeric structure follows to broadening of lifetime distribu-tion (hole size distribution). © T.S. Kavetskyy, V.M. Tsmots, S.Ya. Voloshanska, O. Šauša, V.I. Nuzhdin, V.F. Valeev, Y.N. Osin, and A.L. Stepanov, 2014