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.