| Composite oxide films have attracted increasing interesting in recent years because oftheir potential applications in novel technological devices. The main driving force is thatoxide films in composites are appealing as the interacting between the constituents canlead to enhanced functionalities or multifunctionalities. Ferroelectric BaTiO3（BTO）materials show rich functionalities such as ferroelectricity, piezoelectricity,thermoelectricity, and non-linear optical properties. And they have potential applications insuch as ferroelectric random access memory （FRAM）, infrared detector, spatial lightmodulator, and optical sensor etc. Ferroelectric composite oxide films combined theadvantages of the above two materials and will enhance the functionalities of ferroelectricmaterials.In the present work, we deposited pure BTO, pure Sm2O3, and （BaTiO3）1-x:（Sm2O3）xcomposite films by pulsed laser deposition. The corresponded targets have been fabricatedby solid-state reaction.We investigated and compared the microstructure and physical properties of pureBTO, pure Sm2O3, and （BaTiO3）1-x:（Sm2O3）xcomposite films, including lattice structure,strain, surface morphology, ordering structure, leakage currents, and dielectric properties. Ithas been found that, in the composite films, the BTO and the Sm2O3phases have beenseparated spontaneously. And the vertically alligned nanocolumn structure has beenself-assembled, which contribute to the vertical interface between the BTO and the Sm2O3nanocolumns. The vertical interface resulted in an out-of-plane tensile strain on BTO phasein the composite films. The strain increases with the increasing composition of Sm2O3andreaches a maximum value of+3.73%.We analyzed the leakage and dielectric properties of composite films by fabricating a Pt/（BaTiO3）1-x:（Sm2O3）x/Nb-STO capacitor. We found that1) at the same temperature andelectric field, the leakage currents of the composite films are2to5orders of magnitudelower compared with those of pure BTO films. The main reason is that at the BTO, oxygenvacancies have been reviewed as the main reason of leakage currents. In the compositefilms, because of the vertical interface, there is oxygen transportation or diffusion from theSm2O3to the BTO. It decreased the density of oxygen vacancies in the BTO phase andreduced the leakage current effectively in the composite films.2) by comparing the leakagemechanism, we found that the leakage currents of pure BTO are mainly dominated byinterface effects. In the composite films, the leakage currents show space charge limitedcurrent （SCLC） behaviour, which is a typical bulk effect. The main reason is that in thecomposite films, there are lots of defects along the vertical interface. The charge carriers（mainly electrons） trapped by the defects formed space charges and resulted to the SCLCbehaviour.In conclusion we found that in the （BaTiO3）1-x:（Sm2O3）xcomposited films, thevertical interface play a critical role to determine the leakage and dielectric properties. Thepresent work will contribute to the understanding of growth mechanism, microstructures,interface effects, and leakage behaviour of the composite oxide films. |
