MUONIUM DYNAMICS IN DOPED SI ABOVE ROOM-TEMPERATURE STUDIED BY LONGITUDINAL-FIELD - MU-SR

We report longitudinal field muSR 1/T1 measurements in Si from room te mperature to 850 K. The data in pure Si and Si:B (p-type) can be expla ined in a two-state model where muonium cycles between its positive an d neutral charge states. Within this model, the average muon-electron hyperfine parameter in the neutral state is consistent with muonium at the tetrahedral interstitial site, indicating that at the highest tem peratures measured, neutral muonium spends a significant amount of tim e away from the bond centered site, the calculated potential minimum. Although this is also true for Si:P (n-type) at high temperatures, the data in the region between 300-450 K indicates that at least one othe r state is involved in the dynamics.