Thermal and chemical stability of epitaxial Fe films grown on the Ti-stabilized Al(1 0 0) surface

The important role of interfaces in magnetic thin film devices has driven a strong interest in controlling interface growth, and in the chemical and structural stability of the interfaces at elevated temperatures. Recently, we reported an approach using extremely thin Ti metal interlayers to stabilize the Fe-Al interface, leading to improved epitaxial growth of bcc Fe on Al(1 0 0) surfaces. In the present investigation, the thermal stability of the Fe/Ti/Al interface has been studied using Rutherford backscattering and channeling (RBS/c) and low-energy ion scattering (LEIS). The interlayer structure appears to disorder in two stages, with Al atoms rising to the surface in the initial stage beginning at 200 °C, and diffusion of Fe and Ti into the substrate in the second stage beginning at 400 °C. Rocking curve measurements for backscattered ions near normal incidence on the interlayer structure after annealing to 400 °C indicate significant Fe-Fe shadowing suggesting that the epitaxial Fe film is still well ordered but covered with a few layers of Al atoms as indicated by LEIS results. The enhanced stability of the structure against interdiffusion at elevated temperatures is attributed to the strengthened Ti-Al bonds at the interface.