Detection of diffusional jumps of interstitial Fe in silicon by Mössbauer spectroscopy

Abstract

A technique to create radioactive, interstitial 57Fe atoms in silicon at diffusion temperatures is reported, which allows for the detection of their diffusional jumps by the resulting line broadening in the Mössbauer spectra of the emitted 14 keV γ-radiation. Radioactive 57Mn + ( T 1/2=1.5 min) ions have been implanted into silicon crystals held at 400–700 K. As a result of the annealing of the radiation damage during the 57Mn lifetime, the Mn atoms are found on substitutional lattice sites. In the subsequent decay of 57Mn to the Mössbauer state of 57Fe, an average recoil energy of 40 eV is imparted on the daughter atom. This leads to a replacement into interstitial sites for the majority of the Fe atoms, the remainder remains on substitutional sites. From the temperature dependent line broadening the diffusion coefficients for neutral and ionised interstitial Fe have been deduced.