Structure of multi-oxygen-related defects in erbium-implanted silicon

In a previous report, electron paramagnetic resonance measurements of erbium and oxygen implanted into silicon revealed centres with monoclinic and trigonal symmetry. These centres were tentatively ascribed to different atomic configurations of O and Si atoms surrounding a central Er 3+ ion. In the light of recent calculations concerning the structure and stability of multi-oxygen-related defects in silicon, more sophisticated models have now been developed. The structure of the monoclinic centres observed is attributed to an Er atom sitting at the tetrahedral interstitial site surrounded by six O atoms. In this model the O atoms are arranged in the form of three O interstitial dimers with each of the O atoms located near to the Si–Si bond-centred positions. In the case of the prominent defect centre which exhibited trigonal symmetry, different possible structures for this centre are explored including locating the Er 3+ ion residing at the hexagonal interstitial site surrounded by six O atoms as well as a centre consisting of an O-decorated ring hexavacancy defect.