CEMS and DCEMS investigations of Al-implanted iron

Abstract

α-Fe surfaces were implanted with a nominal dose of 5×10¹⁷ Al ions/cm² at 50 keV and a current density of about 3.7 μA/cm². Samples of different shapes and thicknesses have been used in order to test the influence of heat flow from specimen to target holder during implantation. Integral and energy differential (“depth-selective”)⁵⁷Fe conversion electron Mössbauer spectroscopy (CEMS and DCEMS) were employed. The spectra indicated a magnetic phase characterised by a broad hyperfine field distributionP(B _hf), a non-magnetic phase, and α-Fe. The relative intensity of the non-magnetic phase was enhanced if the thermal contact during implantation became worse. An energy dependence of DCEM spectra in the L-electron range was observed. Model calculations using L-electron weight functions and experimental concentration profiles obtained by secondary neutral mass spectroscopy (SNMS) yielded fair agreement between calculated and experimental phase signals. The results demonstrate that the non-magnetic Fe-Al alloy phase with high Al concentration is located closer to the surface than the magnetic alloy phase, which extends to much larger depth than expected.