Mossbauer study of the proximity gettering of ion-implanted 57Co impurities by B-Si precipitates in Si

We have studied the gettering of ion-implanted Co-57 impurities to amorphous B-Si precipitates in B-implanted c-Si using Mossbauer spectroscopy in conjunction with Secondary Ion Mass Spectroscopy and Transmission Electron Microscopy. Under high-temperature annealing, the Co atoms migrate from their as-implanted state to a gettered state at the B-Si precipitates in the B-implanted layer, while no association between the Co impurities and unprecipitated B is observed. The gettered Co atoms clearly occupy a non-metal-silicide site. The Mossbauer spectrum displays a pronounced quadrupole splitting, closely conforming to the spectrum observed for bulk crystalline B3Si implanted with Co. We therefore tentatively argue that the gettered atoms reside at solution sites within the precipitates and not in their periphery, in agreement with previous indications.