On the isomer shifts of129I impurities implanted in semiconductors

Mössbauer spectra of the 27.8 keV transition in¹²⁹I have been measured with sources of^129mTe implanted in - and -tin and - and -SiC. The spectra mainly show two single line components, just as those obtained in earlier investigations with sources of^129mTe implanted in diamond, silicon and germanium. The component with isomer shift corresponding to a decreased s-electron density relative to the I^– ion is attributed to the substitutionally implanted impurities, that with shift corresponding to an increased s-electron density to interstitial impurities. Plots of the shifts of both component show a linear dependence on the lattice constant for diamond, silicon and germanium and -tin. For SiC, however, the shifts are considerably smaller than expected on the basis of this linear dependence. All shifts can be quantitatively understood on the basis of a simple model that attributes the shifts of the interstitial impurities to a compression in the host lattice and shifts of the substitutional impurities to the combined effect of compression and hybridized bonding.