Physical Properties Manipulation Of Oxide Materials Based On Reconstruction Of Substrate Surface

It has been shown great application in modifying films by using nano-techniques.Anodic aluminum oxide(AAO)nanotemplate is a good choice for horizontal nanostructures,because of the advantages of stability,insulator and low costing.However,vertical structures are not benefit to device fabrication.Herein,faceted sapphire is selected as template for lateral nanostructures,which is regarded as the similar properties of AAO.Sapphire is a type of oxide crystals,with the chemical formula of Al₂O₃.We choose m-plane sapphire to form peak-valley structures on the surface by annealing,which would induce lateral growth latterly.In order to study the effects the lateral nano-confinements,we choose two typical perovskite oxides:La_0.7Sr_0.3MnO₃ and Pb(Zr_0.53Ti_0.47)O₃.They are grown on the reconstructed sapphire substrates.The sapphire substrate is put into a KSL-1500X box furnace to anneal.High quality channels structure were formed.La_0.7Sr_0.3MnO₃ films were grown on the reconstructed sapphire substrate by pulsed laser deposition.Atomic force microscope(AFM)and X-ray diffraction(XRD)were used to characterize the microstructures of the films.The metal-insulator transition(MIT)of La_0.7Sr_0.3MnO₃ is tested by the temperature-resistance(RT)curve using van der pauw method.The anisotropy in MIT is observed.The anisotropy in e paramagnetic-ferromagnetic(PM-FM)trainstion is also studied from the M-H curves.The results of the magnetoresistance show that the resistance of the film was decreasing,and critical temperature of MIT is increasing by applying a magnetic field.Specially,the MIT critical point is verified to be close to Curie temperature,when the current was along with the direction of the Al₂O₃[11-20].Pb(Zr_0.53Ti_0.47)O₃ films are also grown on the same reconstructed sapphire substrates and the polycrystalline films were verified by XRD.The reciprocal space mappings are performed along out-of-plane directions.The surface morphology of the films with different thicknesses were characterized by AFM.The reasonable ferroelectricity and piezoelectricity are shown in the films.And the anisotropy in electric domains switching is existed,due to the lateral nanoconfinements.Because of the different depolarization fields the switching of ferroelectric domains along with in-plane and out-plane directions can reach 180°and 150°,respectively.