Microstructural and electrical properties of BaxSr1-xTiO3 thin films on various electrodes

BaxSr1-xTiO3 (BST) thin films were deposited simultaneously on various electrodes by the sputtering technique. When the substrate temperature was varied, the BST thin film on each electrode showed good crystallinity above 550 degrees C as revealed by X-ray diffraction measurements. The surface morphology, determined by atomic force microscopy, indicated that the roughness of BST thin films on RuO2 was substrate dependent. However, BST thin films on Ru electrodes are smoother and showed no substrate dependence, probably because the precursor surface diffusion length was greater than the sinusoidal perturbations of the wavelength. From the stoichiometry analysis of the BST thin films, the largest dielectric constant was obtained at around a 0.7 molar ratio of Ba in each electrode. BST thin film on Pt/TiN/SiO2/Si showed the highest dielectric constant and the lowest leakage current among the considered samples, displaying great improvement over the thin film deposited onto Pt/SiO2/Si by insertion of a TiN barrier layer. The electrical properties of BST thin films on RuO2 were poorer than those of BST thin films on Ru, mainly because of the rough morphology originating from the rough surface of the bottom electrode.