Charge-state transitions of muonium in germanium

Muonium defect centers in ultrapure germanium show evidence of cyclic charg e-state transitions above approximately 220 K. Detailed analysis of the mag netic-field and temperature dependences of longitudinal muon spin depolariz ation rates reveals contributions from both bond-centered and tetrahedral c age-centered interstitial Mu(0) species involved in separate ionization/cap ture charge cycles. An additional diamagnetic state, observed as a nonrelax ing fraction, is identified as muonium bound in a slowly formed complex whi ch dissociates to join these cycles above 350 K. Capture cross sections and ionization energies are extracted and the most likely identification of st ates and processes responsible for each transition feature are discussed,a consistent picture requires a reinterpretation of earlier data as bidirecti onal site changes for Mu(0) which become active well below 100 K, and indic ates a very shallow potential-energy surface for Mu(0) in germanium as comp ared to silicon. [S0163-1829(99)04627-5].