Nitrogen irradiation of Fe/Si bilayers: nitride versus silicide phase formation

In the course of a systematic investigation of heavy ion-irradiated Fe/Si layers, we have studied atomic transport and phase formation induced by 22-keV N-14(2+) ion implantation in Fe-57(30 nm)/Si bilayers at high fluences. We report here results obtained by Rutherford backscattering spectroscopy, X-ray diffraction, and conversion electron Mossbauer spectroscopy after implantation and post-implantation annealing treatments. The irradiations caused little sputtering, but significant interface mixing. During implantation, iron nitrides, but no silicides were formed, even at the highest nitrogen fluence of 2x10(17) ions/cm(2). When heating these samples in vacuo up to 700degreesC, the iron-rich phases Eepsilon-Fe3N and gamma-Fe4N were produced. Starting at 600degreesC the silicide phase beta-FeSi2 was also identified