NITRIDE FORMATION IN IRON-COBALT SPUTTERED THIN-FILMS

Iron-cobalt thin films (100-1000 nm thick) are evaporated using an ion -beam sputtering device with either neutral (Ar+) ions or reactive (N or N-2(+)) ions as projectiles. The structural characteristions are p erformed by X-ray diffraction, transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS). The Alms deposit ed with Ar+ ions are found bcc in structure and their average grain si ze is of about 20 nm. Cross-sectional TEM analysis shows a fibrous str ucture throughout the film thickness. In films evaporated with N+ or N -2(+) ions, the epsilon nitride phase is identified in addition to a F e-Co bce phase. Dark-field microscopy shows two grain sizes: 50 nm for epsilon nitride and 5 nm for the alpha' structure. EXAFS analysis ind icates that iron and cobalt local environments are identical. Deposits elaborated by sputtering with a mixing of argon and nitrogen show a t hreshold value in nitrogen sputtering gas composition to form nitrides .