Electron polarization and formation probability of bound muonium in CdS and Si

Abstract

Positive muons implanted in CdS and Si create electrically active defect centers that mimic and model the contrasting donor states of interstitial hydrogen in these two materials---a shallow donor in CdS and a deep donor in Si. In the present experiment the polarization of the muonium electron and the formation probability of these states are investigated. We find that the polarization is rather weak and strongly deviates from the polarization expected for a paramagnetic center at low temperatures and high magnetic fields. We assume that the polarization is built up in a precursor stage and is not completed at the time of conversion to the observed final state. The polarization depends on the purity of the samples and is larger for samples with a higher concentration of defects. In addition, the branching ratio between paramagnetic muonium and diamagnetic muon depends on the purity of the samples and on the strength of the magnetic field. These different findings are interpreted in the following model: after implantation, the muon comes to rest at an interstitial site in the unrelaxed lattice. This site is unstable and relaxes to the final configuration. The total energy along the transition path and the strength of the single electron binding to the positive muon during the transformation determine the parameters of the experiment.