A vacancy-related muon species in crystalline silicon

A new muonium centre, termed Mu(V), with weak hyperfine interaction has been discovered recently in crystalline silicon in longitudinal field quenching mu SR (LFQ) experiments (Schefzik et al., Solid State Commun. 107 (1998) 395). The signatures of this species were found in intrinsic, but not in doped samples (dopant concentration larger than 10(16) cm(-3)). The centre is not formed promptly but results from a reaction in which normal muonium transforms into the novel species. Since from LFQ experiments one can obtain only a rough estimate of the hyperfine tensor of Mu(V) it is now determined from zero-field (ZF) mu SR experiments. The hyperfine interaction is found to be axially symmetric around the [110] crystallographic axis with small hyperfine parameters. Properly rescaled it essentially agrees with the hyperfine tensor of the hydrogen centre VH, which has been discovered recently by Bech Nielsen et al. (Phys. Rev. Lett. 79 (1997) 1507) and which has been attributed to hydrogen trapped in vacancies. Accordingly Mu(V) is interpreted as muonium trapped in a vacancy, in agreement with the interpretation given on the basis of the earlier LFQ data. (C) 2000 Elsevier Science B.V. All rights reserved.