2016 Volume 40 Issue 5 Pages 137-147
Fe100-xNix (x = 0-100 at. %) alloy epitaxial films of 10 nm thickness are prepared on Cr(211) underlayers at room temperature by using a radio-frequency magnetron sputtering system. The film growth behavior and the crystallographic properties are investigated by in-situ reflection high-energy electron diffraction and pole-figure X-ray diffraction. bcc(211) crystal epitaxially nucleates on the underlayer for the Fe100-xNix films with x = 0-70 at. %. The bcc structure is stabilized up to 10 nm thickness for the compositional range of x = 0-50 at. %, whereas the Fe40Ni60 and the Fe30Ni70 crystals with bcc structure (x = 60-70 at. %) start to transform into fcc structure with increasing the thickness beyond 2 and 5 nm, respectively. The bcc-fcc phase transformation occurs through atomic displacements parallel to bcc(110) and bcc(101) close-packed planes which are 60° canted from the perpendicular direction. The crystallographic orientation relationship is similar to the Kurdjumov-Sachs relationship. When the x value is increased beyond 80 at. %, metastable hcp(1100) crystal coexists with bcc(211) crystal. The volume ratio of hcp to bcc crystal increases as the x value increases from 80 to 100 at. %. With increasing the thickness, the hcp crystal also starts to transform into fcc structure through atomic displacement parallel to hcp(0001) close-packed plane, which is similar to the case of bulk phase transformation in the Shoji-Nishiyama relationship.