Intra-family transformation of the Bi–Te family via <i>in situ</i> chemical interactions

The Bi–Te binary system, characterized by the homologous series of (Bi2)m(Bi2Te3)n, has always attracted research interest for its layered structures and potential in advanced material applications. Despite the fact that Bi2Te3 has been extensively studied, the exploration of other compounds has been constrained by synthesis challenges. This study reports the molecular beam epitaxy growth of FeTe on Bi2Te3, demonstrating that varying growth conditions can turn the Bi2Te3 layer into different Bi–Te phases and form corresponding FeTe/Bi–Te heterostructures. Our combined analysis using reflection high-energy electron diffraction, high-resolution x-ray diffraction, and high-resolution scanning transmission electron microscopy indicates that specific growth conditions used for the growth of the FeTe layer can facilitate the extraction of Te from Bi2Te3, leading to the formation of Bi4Te3 and Bi6Te3. In addition, by lowering the FeTe growth temperature to 230 °C, Te extraction from the Bi2Te3 layer could be avoided, preserving the Bi2Te3 structure. Notably, all three FeTe/Bi–Te structures exhibit superconductivity, with the FeTe/Bi2Te3 heterostructure enjoying the highest superconductivity quality. The results of magneto-transport measurements indicate that the induced superconductivity displays a three-dimensional nature. These findings introduce a novel method for realizing Bi4Te3 and Bi6Te3 through Te extraction by growing FeTe on Bi2Te3, driven by the high reactivity between Fe and Te. This approach holds promise for synthesizing other members of the Bi–Te series, expanding the functional potential of these materials.