Mössbauer study of ion-beam mixing of Fe/Zr multilayers

Abstract

The Ar-ion-beam mixing of Fe/Zr multilayers is studied in detail by conversion electron Mössbauer spectroscopy (CEMS) and x-ray diffraction (XRD). The dependence of the ion-beam induced amorphization and interfacial mixing on the sublayer thickness and ion dose (1×1013–2×1016 Ar/cm2) is studied systematically for samples with Fe to Zr thickness ratios dFe/dZr=1 and 0.5 and modulation wavelengths Λ=dFe+dZr of 5–80 nm and 7.5–90 nm, respectively. The CEMS results allowed the evaluation of the mixing efficiency from the thickness of the mixed layers. The experimentally determined mixing efficiency was compared with theoretical estimates based on the ballistic collision and thermal spike models, showing good agreement with the predictions of the modified ballistic collision model. For high degrees of amorphization the composition of the amorphous phase formed due to ion-beam mixing is close to the nominal composition of the sample, as revealed by CEMS measurements. These results were compared with those obtained for amorphous Fe-Zr alloys formed by vapor deposition. The XRD results fully agree with CEMS measurements and show that due to ion irradiation the amorphous Fe-Zr phase is formed. The XRD results show that a change of texture occurs from Zr(002) to Zr(100) in the samples with small Λ irradiated with high ion dose. XRD reveals in these samples the formation of the ZrO2 phase.