Barium titanate films for electronic applications: Structural and dielectric properties

Synthesis of the precursors, using research grade materials and locally available facilities, is optimized in order to obtain a suitable sol for BaTiO3. The optimally synthesized BaTiO3 sol is then spun onto Cu substrates to obtain films of thickness similar to 0.5 mu m. The deposited BaTiO3 films are heated up to a temperature of 300 degrees C. Surface and structural changes, with heating, are observed by optical microscope, scanning electron microscope, atomic force microscope, and X-ray diffraction. The surface cracked in some cases but is generally uniform, as seen with SEM and AFM, in case of optimized conditions. The SEM images reveal large crystallites, which are correlated to the XRD observation of tetragonal perovskite structure of these sol-gel films. The AFM scan, however, shows an rms roughness of 35.6 nm for an area of 3 mu m x 3 mu m. Tetragonal perovskite BaTiO3 is obtained at a temperature of as low as 300 degrees C. The dielectric constant and loss angle, in the 30Hz-3MHz range, are calculated at room temperature and up to 200 degrees C. At high frequencies the dielectric constant (similar to 290) and loss angle (similar to 2 x 10(-6)) values indicate the usefulness of such films in electronic applications. The leakage current is also measured at room temperature and a conductivity of 2.0 x 10(-15) S/cm is obtained.