Thermally Stable Sr₂RuO₄ Electrode for Oxide Heterostructures

The use of thermally stable Sr₂RuO₄ electrodes in high-temperature synthesis of oxide heterostructures was investigated. Atomically smooth Sr₂RuO₄ thin films were grown on SrTiO₃(001) substrates by pulsed laser deposition and used as a bottom electrode for ferroelectric BaTiO₃ capacitors grown at temperatures of up to 1000 °C. The thermal stability of Sr₂RuO₄ electrodes was verified by structural and electrical measurements of the ferroelectric BaTiO₃ films. The best growth temperature for the BaTiO₃ films was found to be 900 °C, exhibiting the largest spontaneous polarization, dielectric constant, and pyroelectric response. We conclude that Sr₂RuO₄ films are suitable for use as thermally stable electrodes in heterostructures synthesized at temperatures up to at least 1000 °C and oxygen pressures from 10^-6 to 10^-1 Torr. This range of growth film conditions is much wider than that for other common oxide electrode materials such as SrRuO₃, widening the available process window for optimizing the performance of oxide electronic devices.