Divacancy in silicon: Hyperfine interactions from electron-nuclear double resonance measurements

The Si-G6 EPR spectrum, which is associated with the positive charge state of the divacancy in silicon, was investigated by electron-nuclear double resonance. Hyperfine tensors describing the interaction between the unpaired divacancy electron and ²⁹Si nuclei were determined. With these results, detailed information about the wave function of the defect electron is gathered. Nearly all hyperfine tensors showed a distinct axial symmetry; for the majority the symmetry axis was along one of the 111> bond directions. A total number of 18 tensors was measured: 12 of these belong to a general class shell of atoms, the remaining 6 belong to a mirror-plane class shell. Thus the divacancy electron was probed in a region containing 60 atoms in the vicinity of the defect site. In agreement with a conclusion reported previously, the second largest general class interaction was identified with the nearest-neighbor general class shell of atoms. A complete matching of hyperfine tensors to specific shells of lattice sites was not possible without support by theoretical considerations.