Nanostructure Ceria Thin Film Fabricated Via PLD And The Influence Of Ceria Buffer Layer On The Performance Of Superconductor Layer

Rare-earth oxides with distinguished physical characters are extremely necessary for both practical applications and fundamental studies.So far,CeO₂ has been widely investigated since it is the topmost abundant material among rare-earth oxides materials.An application of CeO₂ films is the substrate and buffer layer for epitaxial YBCO,whose quality will play vital roles on coated high-temperature superconductor's performance.In order to fabricate YBCO coated layer with high quality and carrier density,it'necessary to figure out what the influence of CeO₂layers to YBCO layer is.Empirically,we find out that the morphology of CeO₂ films is very susceptive to the PLD parameters.Therefore,we can make CeO₂ films with specific,uniform nanostructures on their surface,such as nanowires and nanosheets.Because CeO₂ films are also prepared for photoelectrochemistry,a gas-phase chemical reaction catalyst,and sensors,our research is helpful to both fundamental studies and practical applications.In the present work,a pulsed lader deposition approach was used to grow CeO₂films with variety morphology on IBAD-MgO,which is served as the substrate for YBCO layer.The transformation of nanostructure and nanofacests on the surface of ceria thin films was also discussed.1.Surface morphology and facets evolution of CeO₂ nanoarray superstructures fabricated by pulsed laser depositionBy modified PLD growth parameters,we made nanowire and nanosheets clusters array on CeO₂ films.These nanostructures share good unity and anisotropy in terms of morphology and structure.Besides,their shapes,size and density could be modified by changing growth parameters.With the nanostructure morphology evolving,faces transfer is found on these nanofacets.Nanowires have?001?crystal face while nanosheets have?111?crystal face,the XRD and EBSD patterns also reveals that?110?crystal faces appears in the vicinity of two nanostructures.Compared to flat thin film,the oxygen defects density,and UV absorbance of CeO₂ films with nanostructures could be enhanced.2.The effect of surface morphology of cerium oxide layer on the performance of superconducting layerCeria films fabricated at high temperature,and laser fluence tends to have flat surface.While at non-optimized parameters,the roughness of ceria films will increase,although their texture is similar.To films fabricated at low temperature and high oxygen partial pressure,grain defects appear on their surface,and the texture starts broken too.When CeO₂ substrates'roughness increase,YBCO layer's performance are not associated with CeO₂ layer's texture values.Instead,RMS and flat area fraction are key issues for PLD epitaxial multilayers.The SEM images of YBCO/CeO₂ revealed that superconducting layer growthed on flat surface showes a perfect z-axial layered growth with fewer defects.As the roughness of CeO₂ increased,the disoriented grains can be observed,and the critical current density jumped down.When grains'density increased on CeO₂ layer,some holes arose which may ensue from surface tension to misfit dislocations.The critical current density will decrease further.In brief,we investigated the morphology evolve at different growth parameters and different performance of YBCO layers on varied CeO₂ substrates.At last,we introduced a novel meathod to fabricate large-scale,high uniform CeO₂ nanowires and nanosheets via PLD.