Divacancy-tin complexes in electron-irradiated silicon studied by EPR

n- and p-type float-zone silicon containing 10(18)-cm(-3) tin were irradiat ed with 2 MeV electrons to a dose of 10(18) cm(-2) and subsequently examine d by electron paramagnetic resonance (EPR). The p-type material yields only the well-known Si-G29 signal due to the tin-vacancy complex SnV0, whereas the as-irradiated n-type material in addition displays the Si-G7 signal (V- 2(-)), DK4, recently assigned to SnV- in a set of slightly inequivalent con figurations, and a new signal DK1, from a defects with S = 1/2 containing o ne tin nucleus. DK1, which we assign to (SnV-V)(-), undergoes a reversible triclinic-monoclinic transformation at approximate to 15 K. Annealing at 42 8 K removes Si-G29 and DK4 and produces a six-fold increase of Si-G7 and DK 1, the kinetics indicating that about 50% of SnV is transformed into V-2 an d (SnV-V). Annealing at 503 K destroys Si-G7 and DK1, the decay of DK1 bein g linked to the emergence of two new signals DK2 and DK3 from defects with S = 1/2, monoclinic-l symmetry, and two equivalent tin nuclei each, which w e identify as (SnV-VSn)(-) and (Sn2V-V)(-). The structures of the tin-divac ancy complexes are discussed in terms of modifications imposed on the basic divacancy structure by the larger size and lower ionization potential of t he tin atom as compared to silicon. A model is proposed for the migration o f (SnV-V) in the lattice at 500 K, indicated by the process (SnV-V)+Sn-->(S nV-VSn).