NITRIDE FORMATION IN IRON AFTER NITROGEN IMPLANTATION IN A NICKEL TOPLAYER

Nitrogen was introduced in an iron layer underneath a top layer of nic kel. This was done by ion implantation of N into the Ni layer at a tem perature of 200 degrees C. During implantation and subsequent anneals at 250 and 300 degrees C, N diffuses from the Ni layer into the Fe lay er because of a larger affinity of Fe for N than of Ni for N. The conc entration depth profiles of N in the Ni/Fe bilayers, as recorded with the nuclear reaction analysis technique, show at the highest implantat ion dose a peak below the Ni/Fe interface. From structural analysis te chniques (x-ray diffraction and cross-sectional transmission electron microscopy) it was observed that this peak is due to the presence of a n epsilon-Fe3-xN layer below the Ni/Fe interface. It is thus shown tha t epsilon-nitride can be formed in Fe at such low temperatures in the absence of radiation damage.