Study On The Effect Of Hydrogenation Reduction On The Physical Properties Of Transition Metal Oxide Films

Perovskite transition metal oxides will cause a series of strong correlation effects due to the mutual coupling and competition between their orbits,spins,charges,and lattices,which exhibit rich physical properties,such as two-dimensional electron gas,Hall effect,ferromagnetism,and Anti-ferromagnetism and so on.At the same time,it has demonstrated scientific research value and application prospects in various fields such as light field,electric field,magnetic order,and catalytic engineering.These novel effects are caused by the formation of various coordination structures between transition metal cations and oxygen ions and the differences in electronic states.Traditionally,increasing the oxygen vacancy content in the film is done by annealing in vacuum while maintaining the temperature during film growth.However,this method often faces disadvantages such as high temperature,weak reducibility,and low oxygen vacancy content,which makes it possible to control the transition by oxygen vacancy content.The physical properties and structure of the metal thin film material have produced obstacles.At present,the strong reducing agent powder and the oxide film are annealed in vacuum at low temperature,which produces ordered layered oxygen vacancies while maintaining the lattice structure without collapsing,which greatly changes the crystal structure and physical properties.This is for discovering novelty.Lay the foundation for physical phenomena.Based on the above reasons,we will carry out the following work:Chapter 1:We mainly introduce the research background of transition metal perovskite oxide materials,including the research progress of common transition metal oxide films,and introduce the progress of hydrogenation reduction reaction in regulating oxygen vacancies in oxide materials in recent years Progress.Chapter 2:Preliminary introduction to the testing methods used during the master's degree,the preparation process of the film,the hydrogenation reduction technology,and the characterization of the related structure,electricity,magnetism,valence,electron orbit,etc.,and the preliminary successful preparation of the nickelate infinite layer oxide film.Chapter 3:We introduce the regulation of the epitaxial stress on the ordered channels of oxygen vacancies in the lanthanum cobalt oxide oxide film in the hydrogenation reduction reaction.According to the different orientations of the oxygen vacancy channels,the film material has undergone local structural changes and the crystal lattice structure is symmetrical.Sexual breakage and so on.Under the modulation of different stresses,the H-LCO film will appear three different orientations of black stripes.Among them,the Co O₅ quadrangular pyramid lacking apex oxygen ions is forced to stretch in-plane on the compressive stress substrate,resulting in phases.Slanted stripes compared to the substrate.According to the changes in the structure of the stress control film,the H-LCO on the compressively stressed substrate has a ferromagnetic insulation performance near room temperature,thus realizing the effective control of the structure and magnetism of the hydrogenated reduction oxide film by the stress.Spintronics devices provide alternative materials.Chapter 4:We studied the effect of stress on the electrical transport properties of infinite-layer oxide Sr Fe O₂ films.Firstly,a Sr Fe O_2.5 film with a wollastonite structure was grown on a compressive and tensile stress substrate and hydrogenated and reduced.The structure changed from a wollastonite structure to an infinite layered oxide,and high-quality crystals were still maintained before and after the structural transformation.The standard four-point method was used to measure the electrical transport performance,and it was found that it showed good electrical conductivity under a tensile stress substrate,and exhibited insulation properties under a compressive stress.The infinite layer Sr Fe O₂ film was analyzed by XAS and XLD,respectively.The characterization of the 3d electron orbital occupancy,it is found that when the electron orbital occupies the in-plane(92_-2 orbital,the Fe 3d orbital and the O 2p orbital overlap more and show good conductivity.It provides a unique reference meaning for the newly emerging infinite layered oxide of nickelate.Chapter 5:We have made a summary and outlook.First,there are two main tasks.One is the appearance of a new structure of lanthanum cobalt oxide film on a compressive stress substrate and a ferromagnetic insulator near room temperature.The second is to explain the mechanism of Sr Fe O₂ metal-insulator transition from the perspective of electron orbital structure.From the perspectives of perovskite oxide dianionology,energy band,structure,etc.,research prospects explain the value and application of dianionology oxide films in new condensed matter physics materials.