Flexible (Ba 0.7 Sr 0.3 )TiO 3 thick films with mechanically stable dielectric tunability

We report the fabrication and electrical properties of flexible (Ba 0.7 Sr 0.3 )TiO 3 (BST) thick films. Fluorophlogopite mica substrates enable the growth of high-quality BST films because of their high melting temperature and flexible functionality for both concave and convex curvatures. The BST films are flat with quite small roughness of 4.2 nm, and dense without any pores or cracks. The BST films show a small remanent polarization of 3.8 μC/cm 2 , a high dielectric constant of 1390 at 10 kHz, a small leakage current density of 2.2 × 10 –3 A/cm 2 at 200 kV/cm, and a dielectric tunability of 45%. The dielectric tunability is slightly higher for concave bending and is robust with respect to successive mechanical bending up to 10,000 cycles.