Redox Controllable Switch Of Crystalline Phase And Physical Property In SrVOx Epitaxial Films

Due to the unfilled 3d orbital of the transition metal,it exhibits a rich valence state,and its corresponding oxide exhibits a variety of crystal phases and interesting physicochemical properties,which are widely used in many high-tech fields.Some phase transitions of the transition metal oxides have been studied,which found that the physical and chemical properties such as electrical conductivity,magnetic state and electrocatalytic activity can be greatly tuned,further broadening and deepening the application fields of transition metal oxides.In this work,we reveal the invertible structural transition between SrVO3 and Sr2V2O7 films via thermal treatment in oxygen atmosphere or in vacuum.Based on this,the Sr2V2O7 films were successfully synthesized and studied.Property characterization show that the semitransparent and metallic SrVO3 could reversibly switched into transparent and insulating Sr2V2O7,implying potential applications in controllable electronic and optical devices.The content of the paper is as follows:The first chapter mainly introduced the research background of transition metal oxide phase regulation.Firstly,the application of transition metal oxides is briefly introduced.Secondly,we have listed several commonly used phase control methods,such as ionic liquid,high temperature and electrochemical bias;then,some representative transition metal elements are introduced of their phase transition;finally,we introduced the phase regulation of representative vanadium oxides and related studies on SrVO3 and Sr2V2O7.The second chapter mainly introduced the preparation process and structure of SrVOx.Firstly,the preparation of SrVO3 film was introduced based on PLD technology.Then,we introduced the reversible transformation between SrVO3 and Sr2V2O7.Finally,the surface morphology of SrVOx film was characterized by AFM.The third chapter mainly introduced the performance characterization of SrVOx samples.Including the XAS study of the oxidation state,the optical properties were studied by UV-visible near-infrared spectrophotometer,the electrical properties were studied by PPMS,and finally the theoretical calculation was performed using Materials Studio software which also confirmed the electrical optical properties in the experiment.The last chapter is a summary of the main conclusions in this paper.We reveal the redox-induced reversible structural phase transition between SrVO3 and Sr2V2O7 via thermal treatment in oxygen or in vacuum atmosphere.Based on this find,we successfully prepared Sr2V2O7 films with high quality,which is regarded to be difficult to be fabricated previously.These controllable switches of properties imply potential applications in electronic and optical devices.