Argon irradiation of Sn thin layers deposited on Fe substrates

Iron polycrystals deposited with thin films of Sn (100 nm approximately) are irradiated with 300 and 400 keV argon ions at the temperatures of liquid hydrogen, room, and 180 0C. After irradiation, the specimens are examined using optical and scanning microscopy, X-ray microprobe, X-ray diffraction, and He-Rutherford backscattering. The surface structures obtained by irradiation at different temperatures are compared with those resulting from isothermal treatments. It is concluded that at liquid hydrogen temperature the major effect of the irradiation is a large and inhomogeneous, localized sputtering of Sn. Also sputtering dominates at room temperature, although it appears to be homogeneous. Finally at 180 0C, Sn islands and FeSn, FeSn2 crystals develop at the Fe surface. FeSnx precipitates form between 300 to 400 0C when the Sn-Fe bilayer is annealed. Light particle irradiation seems to be effective in reducing thermodynamic barriers for nucleation of the above mentioned precipitates at the Fe-Sn interface. (author)