It was shown that the positron beam technique was a sensitive indicator of the presence of As within the grain boundaries of polycrystalline material. Variable-energy positron beam and secondary-ion mass spectrometric studies were carried out on As+-implanted pre-amorphized samples as a function of dose and rapid thermal annealing temperature. Positron trapping was observed within negatively-charged grain boundaries of the recrystallized polycrystalline material; resulting in a 2% increase in the Doppler-broadening S-parameter value. The infusion of As+ ions into the grain boundaries passivated the charge and reduced their specific positron-trapping rate.

D.W.Lawther, R.Khatri, P.J.Simpson, P.J.Schultz, I.Calder, L.Weaver: Applied Surface Science, 1995, 85, 265-70