1D Atomic Defect Tunnel Structure of Oxygen-Deficient Tungsten Oxide Epitaxial Films and Its Redox Device Applications

Transition metal oxides (TMOs) have potential as active materials for information storage devices due to their diverse structural–chemical–physical properties. Among the many TMOs, tungsten oxide (WO _x ) is a promising candidate because the oxygen concentration can control the crystal structure. The 1D atomic defect tunnel structure of oxygen-deficient WO _x is a suitable platform to realize storage devices. Recently, the relationship between the crystal structure and the optical–electrical–thermal transport properties of WO _x using high-quality epitaxial films has been elucidated and an electrochemical redox device using WO _x films with a 1D atomic defect tunnel structure has been demonstrated using this relationship. Herein, the 1D atomic defect tunnel structure of oxygen-deficient WO _x epitaxial films and its redox device applications are reviewed based on these efforts.