Fe/Sb2Te3 Interface Reconstruction through Mild Thermal Annealing

When coupled with ferromagnetic (FM) layers, topological insulators (TI) are expected to boost the charge-to-spin conversion efficiency across the FM/TI interface. In this context, a thorough control and optimization of the FM/TI interface quality are requested. In this paper, the evolution of the chemical, structural, and magnetic properties of the Fe/Sb₂Te₃ heterostructure, as a function of a rapid mild (up to 200 °C) thermal annealing conducted on the Sb₂Te₃-TI only, is presented. The annealing of Sb₂Te₃ markedly improves its crystalline quality, leading to an increased fraction of ferromagnetic Fe atoms at the buried Fe/Sb₂Te₃ interface and a slight lowering of the Fe layer coercive field. This is quite surprising, since the bi-layer is not subjected to any thermal treatment upon Fe deposition. This method is an efficient tool to clean-up the Fe/Sb₂Te₃ interface, which may be extended to different FM/TI heterostructures. Simultaneously to the interface reconstruction, a constant 20% fraction of FeTe develops at the interface. Since ultrathin FeTe has been reported to be superconducting, these results can open perspective in exploiting phenomena at the edge of magnetism, superconductivity and topology.