Nitride formation in iron after nitrogen implantation in a nickel top layer

Abstract

Nitrogen was introduced in an iron layer underneath a top layer of nickel. This was done by ion implantation of N into the Ni layer at a temperature of 200 °C. During implantation and subsequent anneals at 250 and 300 °C, N diffuses from the Ni layer into the Fe layer because of a larger affinity of Fe for N than of Ni for N. The concentration depth profiles of N in the Ni/Fe bilayers, as recorded with the nuclear reaction analysis technique, show at the highest implantation dose a peak below the Ni/Fe interface. From structural analysis techniques (x-ray diffraction and cross-sectional transmission electron microscopy) it was observed that this peak is due to the presence of an ε–Fe3−xN layer below the Ni/Fe interface. It is thus shown that ε –nitride can be formed in Fe at such low temperatures in the absence of radiation damage.