Speaker
Description
Due to its negative impact on semiconductor devices, iron (Fe) is one of the most
thoroughly investigated impurities in silicon. It is a usual unintended impurity in
silicon manufacturing, functioning as a fast diffuser and severely lowering carrier
lifetimes, especially harmful for solar cells applications [1]. It is still unclear how
defects or other impurities interact with substitutional and interstitial Fe under
implantation conditions. Obtaining an understanding of the behaviour of metal
impurities, such as Fe, in silicon can result in methods for improving gettering
procedures, which transfer metallic impurities to less hazardous areas of devices.
This motivates investigation of the fundamental properties and behaviour of Fe in
silicon at the atomic scale. Techniques such as emission Mössbauer spectroscopy
and emission channelling provide valuable insights into the behaviour of dilute
probe atoms in these contexts. We demonstrate, using 57Fe Mössbauer
spectroscopy following implantation of 57Mn (T½ = 1.5) min. that substitutional Fe in
silicon is not located on the ideal substitutional site, but exhibits cage motion or
jumps via saddle sites, located 0.17(3) Å from the ideal substitutional site. In the
temperature range from 300 K to 500 K, the jump rates follow an Arrhenius
behaviour, with rates in the vicinity of 10^7-10^8 Hz and an activation energy of
0.18(3) eV. Our data also suggest compressive strain on substitutional sites and
relaxing strain on interstitial sites when the implantation is below ~450 K. These
findings provide new insights into the atomic-scale behaviour of Fe in silicon, which
is essential for improving material processing and device performance.
