Redox Controllable Switch of Crystalline Phase and Physical Property in SrVO $_{x}$ Epitaxial Films

Transition-metal oxides have attracted much attention due to its abundant crystalline phases and intriguing physical properties. However, some of these compounds are difficult to be fabricated directly in film form due to the ease of valence variation of transition-metal elements. In this work, we reveal the reversible structural transition between SrVO $_3$ and Sr $_2$ V $_2$ O $_7$ films via thermal treatment in oxygen atmosphere or in vacuum. Based on this, Sr $_2$ V $_2$ O $_7$ epitaxial films are successfully synthesized and studied. Property characterizations show that the semitransparent and metallic SrVO $_3$ could reversibly switch into transparent and insulating Sr $_2$ V $_2$ O $_7$ , implying potential applications in controllable electronic and optical devices.