Influence Of Substrate Annealing On The Growth Of La_0.5Ba_0.5CoO₃Films

film, which has a cubic perovskite structure, is a kind of new functional material. It is of increasing interest due to its wide range of electrical transport properties and magnetic properties. Also it shows some unusual physical phenomena such as Giant Magnetoresistance Effect, Negative Thermal Expansion etc. It has potential application in various novel devices for example catalyst, ultra sensitive gas sensor as well as electrodes in solid oxide fuel cell (SOFC) etc.Using the reactive radio-frequency magnetron sputtering method, La0.5Ba0.5CoO3thin films were deposited on the different substrates. The substrates were annealed in air at the temperatures of1200,1350, and1400℃respectively. The LBCO films on the pretreated substrates were studied with the structural and morphological characterization using X-ray diffraction and atomic force microscopy. The results are summarized as follow.1. It was found that the surface of MgO substrates is changed to be step-like after annealing. All of the as-grown films are pure LBCO phase with highly oriented along the a-axis. The (p-scan confirms that the LBCO films have the single-crystal features. The rocking curve measurement of the films shows that the full width at half maximum decreases from2.17°to1.27°with the increase of annealing temperature from room temperature to1400℃. For the as-received substrate and the substrates annealed at1200℃,1350℃and1400℃, the correlation length of the self-affine morphology are216,87,222, and168nm respectively.2. Annealing has a significant influence on the substrate surface morphology. After annealing, The surface roughness is increased to1.29nm due to the appearance of steps. By XRD analysis, it is found that there are steps. For the as-received substrate and the substrates annealed at1350℃, the correlation length of the self-affine morphology are211and78nm, the average crystal size decreased.3. It was found that the unannealed LAO surface roughness is1.17nm. After annealing, AFM images showed that there is island structure found on substrate surfaces and the roughness is decreased to0.66nm. All of the as-grown films are pure LBCO phase with highly oriented along the a-axis. While after annealed, the film peaks became less apparent. AFM images showed that there are a lot of island structure found on film surfaces, the surface roughness is12.3nm. The correlation lengths of the self-affine morphology are270and961nm.