Physical Property Control Of Ferrioc Materials Based On Reconstruction Of Substrate Surface

Porous anodized aluminum oxide?AAO?is widely used in microelectronics due to its chemical stability and insulating properties.It has been used as a nano-template for preparing nanostructures.However,only vertical nanostructures can be prepared with this template due to its structural limitation,and thus limit their device applications.Therefore,research on horizontal nanostructures is necessary.In this work,crystal sapphire?Al₂O₃?,which shows consistent chemical properties as AAO,was selected as the substrate.The surface of m-plane sapphire was reconstructed by high temperature annealing,and decomposed spontaneously to form a channel of peak-valley structure,thus becoming a natural horizontal nano template.In order to study the role of this horizontal nano-templates,two typical ferroic materials,inorganic VO₂ and organic PVDF-TrFE were grown on the templates respectively.The effect of the templates on the structure and properties of the two materials was investigated.VO₂ films were grown on the reconstructed sapphire substrate using pulsed laser deposition?PLD?.The microstructure of the films was characterized by atomic force microscopy?AFM?,X-ray diffraction?XRD?and transmission electron microscopy?TEM?.The results showed that the structure of the sapphire substrate channel guided double epitaxial growth of VO₂ films along both sides of the channel.Besides,we also paid attention to the metal-insulator transition?MIT?characteristics of VO₂ by measuring its temperature-resistance?R-T?property through Van der pauw method,and found anisotropy at different channel orientations of the reconstructed sapphire substrate.The?-phase PVDF-TrFE nanostructures were successfully prepared on a reconstructed sapphire substrate by chemical solution deposition?CSD?and recrystallization.The surface morphology was characterized by AFM.For PVDF-TrFE with different thicknesses,nanorods and thin film structures were form and guided by the surface of the substrate.XRD tests showed that they were all?-phase PVDF-TrFE.The piezoelectric and ferroelectric properties were characterized by PFM,and were different for the two morphologies.Moreover,the in-plane ferroelectricity exhibited better performance than the out-of-plane under the confinement of nano-templates.