Dielectric properties of (Ba,Sr)TiO3 MOD films grown on various substrates

(Ba_0.7SrO_0.3)TiO₃ (BST) double layer capacitors with Pt electrodes were fabricated under identical conditions on different substrates: SiO₂/Si(111), r-plane sapphire, polycrystalline alumina Al₂O₃ (99.6%), Zirconia/Yttria Stabilized Alumina (ZYSA) and glazed polycrystalline alumina. The formation of the crystalline structure of BST films, grown by metal-organic decomposition (MOD) at various thermal processing conditions, leads to significant change in the dielectric properties of the BST films. By preparing BST films of the same thickness and under the same processing conditions, we observed that they possess higher capacitance when grown on all types of alumina-based substrates compared to those on SiO₂/Si substrates. The higher capacitance on alumina were always associated with larger dissipation factors, and lower or similar leakage current densities. The final tuning of dielectric properties of BST double layer capacitors on non-silicon substrates was correlated to the processing conditions. Furthermore, the processing parameters and the type of lower electrode should be optimized individually for each specific substrate. The lowest achieved leakage current density of Pt/BST/Pt capacitor (500×500 μm²) on glazed alumina was 2.8×10^-9 A/cm² at 200 kV/cm with capacitance per unit area of 27 fF/μm².