Structural and Ferroelectric Properties of Ba₂NaNb₅O₁₅ Thin Films on La-Doped SrTiO₃ Substrates

The c-axis-oriented Ba2NaNb5O15 (BNN) thin films were prepared on La0.05Sr0.95TiO3 substrates by pulsed laser deposition. The c-axis orientation and surface roughness of the BNN thin films depend on oxygen gas pressure (Po-2) and substrate temperature (T-sub) during the deposition. When Po-2 and T-sub were fixed at 5.0 mTorr and 700degreesC, respectively, the BNN thin film exhibited a strong c-axis orientation and a smooth surface. Its remanent polarization (P-r) and coercive field (E-c) were 2P(r) = 48.5 muC/cm(2) and 2E(c) = 290 kV/cm, respectively. The band gap of this strongly c-axis-oriented BNN thin film was about 3.1 eV, which accords with that of the BNN single crystal.