Distribution of ion-implanted nitrogen in iron alloys investigated by AES

The depth distribution and the lateral distribution of nitrogen after impla ntation by means of plasma immersion ion implantation (PIII) in ferritic al loys with 0.3 wt.-% Al and 3.6 wt.-% Cr has been studied by scanning Anger election spectrometry (AES), To get information about the chemical state of nitrogen and to improve the detection limit methods of data analysis (fact or analysis, LLS) have been applied to depth and line profiles, respectivel y. Thereby the detection limit for nitrogen was reduced from 6% to 1%. The nitrogen distribution is laterally homogeneous in the near surface regi on only. Depth profiles obtained at several points within the sputter crate r showed that the in-depth distribution of nitrogen varies markedly between different points on the sample and from sample to sample. The nitrogen con centration ill the implantation maximum corresponds to Fe2N1-x (x approxima te to 0.04 ... 0.18), A remarkable feature are grains having a 10 mu m wide seam rich in N and a nearly nitrogen-free grain's interior. The N/Fe ratio determined from line profiles show that the outer layer of the grains is h as almost the exact composition Fe4N and the transition to the nearly nitro gen-free grain's interior (c(N) I 1%) occurs within 1 ... 4 mu m. The same shape of the N(KLL) peak was found in depth profiles and line scan s, respectively, and it corresponds to gasnitrided samples gamma'-Fe4N and epsilon- Fe2N1-x.