Study of the location of implanted fluorine atoms in silicon and germanium through their nuclear quadrupole interactions

Time Differential Perturbed Angular Distribution (TDPAD) measurements of the nuclear quadrupole hyperfine parameters for ¹⁹F* implanted into amorphous, polycrystalline and crystalline silicon and germanium are reported and reviewed. Two signals are observed in the crystalline materials ( ≈ 35 and 23 MHz in silicon, ≈ 33 and 27 MHz in germanium) while only one is detected in the amorphous and polycrystalline samples ( ≈ 22 MHz in silicon, ≈ 27 in germanium). Impurity sites in these materials were modeled using a Hartree-Fock cluster procedure. The Intrabond, Antibond, and Substitutional sites in the bulk were studied in both silicon and germanium. The ATOP and Intrabond Surface sites were also studied in silicon and the results extended to germanium. Lattice relaxation effects were incorporated by employing a geometry optimization method to obtain minimum energy configurations for the clusters modelling each site. The electronic wave functions were obtained for each optimized cluster by applying Unresctricted Hartree-Fock theory, and these wave functions were used to calculate the nuclear quadrupole hyperfine parameters at the site of the fluorine nucleus. Comparison of the theoretical hyperfine parameters to the experimental values indicates that ¹⁹F* located in the Intrabond and Intrabond surface sites could readily explain the higher frequency signal that has been observed. ¹⁹F* in the Antibond and the surface ATOP sites yield hyperfine parameters consistent with the low frequency signal observed in the crystalline materials and the single signal observed in the amorphous (or polycrystalline) materials. Examination of these two sites, in view of other available experimental evidence including the temperature dependence of the TDPAD signals, leads to the conclusion that the lower frequency signal is due to ¹⁹F* implants which have come to rest at the site of dangling bonds in the bulk. These dangling bonds are created as a result of damage generated in the individual collision cascades during the implantation process.