57Fe Mossbauer investigations in p-type Silicon Germanium single crystals

Radioactive Mn-57(+)(T-1/2 = 1.5 min) ions have been implanted at the ISOLDE facility at CERN with 60 keV energy to fluences <10(12)/cm(2) into p-type Si1-xGex (x < 0.1) single crystals held at 300-600 K. The implantation and annealing processes result in the majority of the implanted Mn ions occupying substitutional lattice sites. In the subsequent Mn-57 nuclear beta(-)-decay to the 14.4 keV Mossbauer state of Fe-57 (T-1/2 = 100 ns), an average recoil energy of 40 eV is imparted to the Fe-57 daughter atoms which results in a large fraction being expelled into tetrahedral interstitial sites and the creation of a vacancy. The remainder occupies substitutional sites. This technique of recoil production of Fe-57m(I) thus allows for the study of the diffusion characteristics of interstitial Fe. From the temperature dependent line broadening, the activation energies have been determined and decrease with increasing Ge concentration which contributes significantly to the increase of the jump frequency. A similar result has been obtained in n-type SiGe but there the values for the activation energies were much higher.