Electrical properties and crystal structures of (Ba,Sr)TiO3 films and BaRuO3 bottom electrodes prepared by sputtering

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( Ba,Sr)TiO 3 (BST) films were synthesized on BaRuO3 (BRO) using radio-frequency magnetron sputter deposition. Conductive (∼1 mΩ cm) BRO layers of (110) texture were produced at a deposition temperature Td=400 °C, about 200 °C lower than that of SrRuO3. The BST (100 nm) deposited on the BRO showed a (110) preferred orientation and crystallization formation at temperatures as low as 200 °C. An interfacial layer and the local epitaxial growth of BST on BRO layers within columnar grains were confirmed by high-resolution transmission-electron microscopy studies. Uniform I–V characteristics (I<1×10−7 A/cm2) for bias voltages in the range 0.0–3.0 V of all the BST films deposited within Td=300–500 °C were observed. The dielectric constants of the BST films (e.g., εr=300 at Td=400 °C) are considerably higher than those generally achievable for the same Td by using Pt bottom electrodes. The dependence of the annealing atmosphere (N2 and O2) of the dielectric constants was studied and attributed to a diffused BST/BRO interfacial layer which is semiconductive in a reduced state and insulating in an oxidized state.