Detection of substitutional and interstitial Fe in silicon by Mossbauer spectrocopy

A novel approach to create radioactive, substitutional and interstitial **5**7Fe atoms in silicon at elevated temperatures is reported, which allows for Mossbauer studies of the emitted 14 keV gamma-radiation. Radioactive **5**7Mn**+ (T//1/////2 = 1.5 min) ions have been implanted at the ISOLDE facility at CERN with 60 kev energy to fluences less than 10**1**2/cm**2 into silicon crystals held at 400-800 K. As a result of the annealing of the radiation damage during the **5**7Mn lifetime, the Mn atoms are found on substitutional lattice sites. In the subsequent decay of **5**7Mn to the Mossbauer state of **5**7Fe an average recoil energy of 40 eV is imparted on the daughter atom. This leads to a relocation into interstitial sites for the majority of the Fe atoms, the remainder remains on substitutional sites. Thus the Fe electronic and vibrational properties on both lattice sites can be studied. A few diffusional jumps of interstitial Fe during the lifetime of the Mossbauer state (T//1/////2 = 100 ns) have been observed by a broadening of their Mossbauer line at greater than 450 K. At the highest temperatures a new line occurs in the spectra, the possible nature of this line will be discussed. 24 Refs.