Variable-energy positron annihilation spectroscopy and Rutherford back-scattering channelling were used to study the damage which was introduced by the implantation of n-type Czochralski samples with Co+ ions, at 375C, to fluences ranging from 2 x 1014 to 1016/cm2. It was found that, for fluences of 2 x 1014 and 1015/cm2, only one type of defect was detected. This was distributed evenly to a depth of 1; about 2.5 times that of the implanted ions. At fluences of between 4 x 1015 and 1016/cm2, a second type of defect was observed; to a depth that was equal to the range of the implanted ions. These defects were tentatively suggested to be vacancy-impurity complexes and vacancy clusters, respectively. No defects were detected, using Rutherford back-scattering channelling, in samples which had been subjected to fluences of 2 x 1014 or 1015/cm2. However, defects were observed at higher fluences. Upon annealing (1000C, 60s) samples which had been subjected to these higher fluences, large cavities (greater than 1nm) were detected by means of positron annihilation spectroscopy. This behavior was consistent with a dissolution of silicide precipitates which had been observed using transmission electron microscopy. It was suggested that the formation of the cavities depended upon the presence of vacancy clusters following ion implantation. An increase in the number of extended defects was observed, using Rutherford back-scattering channelling, after annealing at up to 1000C.

A.P.Knights, G.R.Carlow, M.Zinke-Allmang, P.J.Simpson: Physical Review B, 1996, 54[19], 13955-61