Interdiffusion in Heusler film epitaxy on GaAs(001)

Abstract

We report the role of interdiffusion in molecular beam epitaxy of the binary Heusler alloy system Fe${}_{1\ensuremath{-}x}$Si${}_{x}$/GaAs(001), employing a variety of complementary techniques that, in their combination, provide quantitative insight into the dynamics of the involved processes. The main properties of the investigated Fe${}_{0.84}$Si${}_{0.16}$ and Fe${}_{0.76}$Si${}_{0.24}$ films---growth, epitaxy, crystallographic order, interface quality, saturation magnetization, coercive field, and magnetic anisotropy---are in perfect agreement with the literature. Additionally, our results reveal a strong interdiffusion of Fe and Si into the GaAs substrate as well as of As and Ga into the Fe${}_{1\ensuremath{-}x}$Si${}_{x}$ films, creating intermixed layers of 2--3-nm thickness in both film and substrate. Interdiffusion is dominant already at moderate growth temperatures required for crystallographic ordering, thus demanding new concepts including appropriate diffusion barriers for the development of ferromagnet/semiconductor hybrid systems.