Study On Preparation Of Perovskite SmNiO₃ Epitaxial Thin Films And Tuning Of The Metal-insulator Transition By Electric Field

The metal-insulator transition has always been an important topic in condensed matter physics.Among materials that have metal-insulator transition,perovskite-type nickelates?RNiO₃,R?La?are typical with a sharp metal-insulator transition,which make them have broad application such as electronic devices,optoelectronic devices and so on.However,the metal-insulator temperatures of RNiO₃ materials are not at room temperature.Therefore,tuning the metal-insulator transition temperature to room temperature is beneficial to practical application.In this thesis,we select SmNiO₃ whose metal-insulator transition temperature is near 400K and grow SmNiO₃ epitaxial thin films on LaAlO₃ single crystal substrate by pulsed laser deposition.And we study the effect of oxygen partial pressure on metal-insulator transition temperature.Based on the research of dielectric properties of ionic liquids,we select DEME-TFSI as the gate insulation layer to study the tuning of metal-insulator transition temperature by electric field,because of strong carrier tuning ability provided by electric double layer structure.The first chapter introduces the research background and the latest research progress of the related works.Firstly,band theory and four types of transitions were introduced.Then,the metal-insulator transition of strongly correlated electron system was introduced.Finally research progress and metal-insulator transition of perovskite nickelate and ways to tune the metal-insulator transition temperature were explained.The second chapter describes the preparation method and characterization tools of SmNiO₃ thin films used in this thesis.The third,fourth and fifth chapters are the main parts of the thesis.In the third chapter,we mainly study the effect of oxygen partial pressure on crystal structure,surface morphology and transition temperature of SmNiO₃ thin films.In the fourth chapter,dielectric properties of two kinds of ionic liquids?DEME-BF₄ and DEME-TFSI?were studied.In the fifth chapter,high-quality SmNiO₃ thin film was used as the channel layer and ionic liquid was used as the gate insulation layer,an electric double layer transistor was made.By applying the gate voltage,we studied the effect of electric field on the metal-insulator transition temperature of SmNiO₃ epitaxial thin film.