Design and preparation of stress-free epitaxial BaTiO₃ polydomain films by RF magnetron sputtering

Domain structures of BaTiO₃ thick films grown on (100) SrTiO₃ single-crystal substrates were engineered using an RF magnetron sputtering deposition process. By tuning the sputtering power and cooling rate and using an off-axis sputtering technique to prepare conducting perovskite oxide bottom electrode with heteroepitaxial quality, we have deposited epitaxial tetragonal single-domain and polydomain BaTiO₃ films with a self-assembled three-domain architecture. The electrical properties and microstructure of the BaTiO₃ films were characterized, and a c/a₁/a₂ cellular polydomain structure was clearly observed in as-grown films by optical microscopy. Such a polydomain structure was a consequence of a complete relaxation of misfit stresses of the film. Engineering of this self-assembled microstructure has great potential in providing large, field-tunable pyroelectric and electromechanical responses in next-generation microelectronic devices and micro-electro-mechanical systems (MEMS).