Oxygen-related muon species in crystalline silicon

A new muonium centre, termed MuX, with anisotropic hyperfine interaction has been discovered recently in crystalline silicon in transverse-field muon spin rotation experiments (Schefzik et al., Philos. Mag. B 79 (1999) 1561). Its hyperfine tensor is very close to that of bond centred muonium (MuBC). The signature of MuX is only observable in samples containing oxygen in a concentration which is higher than that of the donors or acceptors. This indicates that MuX is related to an oxygen–muonium centre. In the present work we have carried out a study of the temperature behaviour of the MuX signal on a sample showing a very pronounced MuX signature. The observations clearly show that the MuX signal, on the one hand, and the MuBC signals, on the other, have an identical temperature dependence.