An approach is described for stabilizing metal-metal epitaxial interfaces using a thin metallic interlayer. Rutherford backscattering and channeling techniques along with low-energy electron diffraction and keV He+ ion backscattering are used to demonstrate that an atomically thin layer of Ti deposited at the Fe-Al interface, a system well known for considerable intermixing at room temperature, forms a thin interface alloy that prevents interdiffusion and improves epitaxial growth of Fe on Al(100). The structure is stable up to about 200 degrees C.
Chemical roughness and alloy formation at metallic interfaces can significantly degrade the performance of multilayer thin film magnetic device structures. We have investigated the use of Ti interlayers, one or two atoms thick, to stabilize the interface for ordered growth of Fe films on Al(100), a system characterized by considerable interdiffusion at room temperature. The practicality of the interlayer concept is strongly coupled to the stability of the interlayer at elevated temperatures. In this investigation we have characterized the structure of thin Ti layers on Al single crystal surfaces as a function of temperature using Rutherford backscattering and channeling and low-energy ion scattering. The Ti layers are shown to be stable up to temperatures of about 675 K, at which point diffusion of Ti into the Al lattice occurs. Channeling measurements show that the Ti atoms sit on Al lattice sites as substitutional impurities. The stability of the Ti film appears to increase with the packing density of the Al surface, being slightly more stable for the close-packed Al(111) surface, and diffusing into the more open Al(110) surface at a lower temperature.
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