Growth of 0.1(Bi,Na)TiO₃–0.9BaTiO₃ epitaxial films by pulsed laser deposition and their electric properties

Abstract

TiO 3 0.9BaTiO 3 thin films were deposited by pulsed laser deposition as a candidate of lead-free thin films with a positive temperature coefficient of resistance for micro-thermistor applications in microelectro mechanical system devices. ( 001)-oriented epitaxial tetragonal films with a unity (Bi + Na + Ba)/Ti ratio were grown at 675°C under a total pressure of 50 mTorr. The obtained films showed improved insulating properties and clear ferroelectricity. The Curie temperature was estimated to be 200°C by the high-temperature X-ray diffraction measurement, which was almost the same as the reported value for the ceramic.

Achieving High Piezoelectric Performance across a Wide Composition Range in Tetragonal (Bi,Na)TiO3–BaTiO3 Films for Micro-electromechanical Systems

“…According to our previous reports, tetragonal (Bi,Na)TiO 3 –BaTiO 3 films ( x = 0.06–1.0) deposited on SrTiO 3 substrates are epitaxial films and were subjected to detailed XRD analysis. 41 , 42 These results show that the volume fraction of the (100) orientation and non-180° domain fraction of the (100)/(001)-oriented ferroelectric films are determined by the thermal strain from the substrate; the thermal expansion coefficient of the SrTiO 3 substrate is 10.9 × 10 –6 /K, 43 which is larger than that of (Bi,Na)TiO 3 –BaTiO 3 (approximately 6 × 10 –6 /K). 33 Thus, the (Bi,Na)TiO 3 –BaTiO 3 film on the SrTiO 3 substrate was confirmed to have a pure (001) orientation and c -domain structure with a polarization axis along the out-of-plane direction, which can be attributed to the in-plane compressive strain experienced during the cooling process after deposition.…”