The electric quadrupole hyperfine interaction at sites of ion-implanted fluorine in amorphous and crystalline silicon

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Abstract
Two unique fluorine sites in silicon with axially symmetric electric-field gradients (EFG) are reported. Both sites were produced by recoil-implantation into silicon via the 19F(p, p')19F* nuclear reaction and for each recoil site the quadrupole coupling constant, nu Q, of the excited 197 keV nuclear state, 19F*, was obtained by means of the DPAD technique. One site with nu Q=23.1 MHz and randomly oriented EFG is formed both in amorphous and crystalline material. The other site with nu Q=34.9 MHz is formed only in crystalline silicon, with the EFG symmetry axis along the (111) direction. An attempt to determine the lattice location of that latter fluorine site by means of the channelling technique has been unsuccessful; migration of fluorine which may have effected the channelling measurements is discussed and held responsible.