Cavities in silicon investigated with the PAC-probe In-111

The perturbed angular correlation technique (PAC) was used to study the cre ation and development of He-induced cavities. In order to investigate the i nteraction of Indium atoms with cavities in Silicon the Bonn isotope separa tor was used to implant overlapping profiles of He (10 keV) and radioactive In-111 (160 keV) into undoped FZ-silicon. To get insight into the cavity f ormation mechanism samples were prepared with various He-doses (0.6, 2 and 6 X 10(16) ions/cm(2)). The samples were measured directly after implantati on and after different annealing steps (t(hold) = 10 min, T = 500-1100 degr ees C). Further, different implantation and annealing sequences were used. At higher He doses (2 and 6 X 10(16) ions/cm(2)) we find a large fraction o f In-111 probe atoms subjected to an electric field gradient (EFG) correspo nding to a quadrupole interaction frequency (QIF) of nu(Q) = 411(6) MHz wit h eta = 0.25(4). The corresponding defect configuration is formed most effe ctively after He implantation into annealed, In-111 doped Si. This and the affinity of In to vacancies leads us to the assumption that, similarly to t he situation in metals, the Indium atoms act as nucleation centres for vaca ncy clusters (cavities) and are situated on the inner walls of the cavities .