Properties of cobalt in FZ and CZ silicon studied by Mössbauer spectroscopy

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Abstract
Mössbauer effect investigations were performed on the Co system in n- and p-type silicon [floating zone (FZ) and Czochralski (CZ)]. The samples were saturated with Co-57 between 1080 and 1100 °C and quenched and annealed isochronically up to 600 °C and isothermally for times up to 22 h. In n-type material, a transformation of a quadrupole doublet into a single line with increasing annealing temperature is observed, independent of the P and O concentrations. In p-type samples, three quadrupole doublets are found after quenching, which are attributed to different CoB pairs following an interpretation given by Bergholz [Physica, 116B, 312 (1983)]. These quadrupole doublets transform during annealing at first into the quadrupole doublet and then into the single line found in n-type silicon. This transformation is interpreted as the decomposition of the CoB pairs followed by the precipitation of the interstitial Co. The transformation observed in n-type Si is interpreted as a morphological change of the CoSi2 precipitate.