The structural damage which resulted from the implantation of 5keV B+ ions into float-zone material was investigated by means of positron annihilation spectroscopy, using a tunable monoenergetic beam. Four samples, which were exposed to fluences ranging from 2 x 1012 to 2 x 1015/cm2, were studied. The positron annihilation spectroscopy results demonstrated the applicability of the technique to the study of vacancy-type defects which were created by very low-energy ion implantation. The ion depth profiles which were determined by secondary ion mass spectrometry exhibited tails which extended well beyond the predicted range. This was attributed to ion channelling. Positron annihilation spectroscopy, when extended by making repeated measurements after the precise etching away of 40 to 140nm of material by anodic oxidation, showed that the vacancy-type defect depth profiles also extended far beyond the predicted limit. The ratio of defects to ions increased with depth; thus suggesting that the defect tails were not simply related to the implanted ions, but that there might also have been a contribution which arose from post-implantation defect diffusion.

Positron spectroscopy of vacancy-type defects in Si created by 5keV B+ implantation F.Malik, P.G.Coleman, A.P.Knights, R.Gwilliam, A.Nejim, Y.Ho: Journal of Physics - Condensed Matter, 1998, 10[46], 10403-8