Positron beam annihilation Doppler-broadening and Raman studies were carried out on H-plasma treated and annealed p-type Cz-Si. Samples were treated by a 13.56MHz H-plasma for 2h at about 30C and 250C, respectively. Annealing was done in air between 100 and 600C for annealing times between 600s and 8h. The Raman spectra of the RT treated samples showed no (or only very weak) H2-molecule signals, in contrast to the samples H-plasma treated at 250C. Raman intensity changes as a function of temperature were observed, which were attributed to the evolution of voids or platelets. The positron annihilation data correlate with these results, since annealing of the RT plasma treated samples reduced the Doppler-broadening S-values with increasing temperature and/or annealing time. Together with an increasing positron diffusion length this suggested that defects acting as positron trapping centers were (partially) annealed out. For the sample plasma treated at 250C the following depth dependent behavior of the Doppler parameters was found. Below 100nm depth the Doppler parameters follow the same trend as those of the RT treated samples. In a zone between 100 and 200nm depth the S

parameter strongly increases after annealing at 600C. This was attributed to the formation of positronium (Ps), indicative for the presence of nano-cavities capable of trapping molecular H in this region.

Positron Beam and Raman Analysis of Hydrogen Plasma Treated and Annealed Cz-Si. H.Schut, A.van Veen, S.W.H.Eijt, R.Job, A.G.Ulyasin, W.R.Fahrner: Nuclear Instruments and Methods in Physics Research B, 2002, 186[1-4], 94-9