Electron-nuclear double resonance of titanium in silicon:Si29ENDOR

The Si-NL29 EPR spectrum, which is associated with the positive charge state of interstitial titanium in silicon, was investigated by electron-nuclear double resonance. Hyperfine-interaction parameters of 17 shells of silicon neighbors, comprised of 214 atoms, could be determined. These parameters are analyzed in a linear combination of atomic orbitals treatment that takes the symmetry properties of the ($t_2$ ${)}^3$ paramagnetic state into account. This analysis yields a minimum value for the spin density that is transferred from the ${\mathrm{Ti}}^{+}$ ion to the surrounding Si atoms. In a tentative assignment of hyperfine tensors to specific lattice sites a spin transfer of at least 40% is derived. This can resolve the apparent contradiction between reduced central-nucleus hyperfine field and absence of ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ hyperfine interactions in EPR.