Structural, Superconducting and Magnetic Properties of Oxygen‐Annealed Fe ₁₊ <i> _y </i> Te Thin Films

ABSTRACT Fe‐based superconductors have attracted much attention. Among them, FeTe is unique in the series of FeSe 1‐ x Te x with absence of superconductivity. Interestingly, Fe 1+ y Te thin film shows superconductivity after oxygen annealing, and the mechanism is still elusive. This study investigates structural, superconducting, and magnetic properties of a series of Fe 1+ y Te thin films (FeTe:O x ) annealed under different oxygen partial pressures. Scanning transmission electron microscopy is used to examine the amount and distribution of excess Fe, the migration of excess Fe toward the film surface, and the structure and distribution of the iron oxide layer formed on the film surface. Exchange bias emerges at the interface between the ferromagnetic iron oxide and FeTe:O x , persisting in the superconducting state. Theoretical calculations suggest the occurrence of both interstitial oxygen and substitutional oxygen, and suppression of AFM order by the former, which can account for superconductivity. This work is helpful for understanding the interaction of oxygen with Fe 1+ y Te and mechanism of superconductivity for FeTe:O x thin films.