FERRO- AND PIEZOELECTRIC CHARACTERISTICS OF BOTTOM-UP FABRICATED CaBi4Ti4O15 FILMS WITH PREFERRED ORIENTATION

Abstract

ABSTRACT Polar-axis oriented CaBi4Ti4O15 (CBTi144) films were fabricated on Pt foils by a bottom-up method using a complex metal alkoxide solution. The oxygen ambient during crystallization of the films impacted the crystal perfection, crystallite size and the ferroelectric properties. The 500 nm-thick film crystallized in oxygen flow had single columnar structure and in-plane grain size of about 200 nm. The ferroelectric properties were improved. The remanent polarization, Pr and coercive electric field, Ec of the film enhanced as 33.6 μC/cm2 and 357 kV/cm, respectively, at an applied voltage of 50 V. Voltage applied for full polarization switching was lowered by controlling oxygen stoichiometry of the film. The piezoelectric constant, d33 of the films, which was evaluated by PFM without using top electrodes, was enhanced to about 50 pm/V. Indeed, the polar-axis oriented CBTi144 films would open up possibilities for novel devices as Pb-free ferroelectric materials.