Synthesis and characteristics of nature-superlattice-structured Bi3TiNbO9-Bi4Ti3O12 ferroelectric thin films by MOD

Natural-superlattice-structured ferroelectric thin films, Bi3TiNbO9-Bi4Ti3O12 (BTN-BIT), have been synthesized on Pt/Ti/SiO2/Si by metal organic decomposition (MOD) using BTN-BIT (1 mol:1 mol) solution. BTN-BIT films show natural-superlattice peaks below 2θ = 20o in X-ray diffraction patterns, which indicate that the BTN-BIT films annealed at 700-800 deg. C in O2 ambient are consisted of iteration of two unit cells of Bi3TiNbO9 and one unit cell of Bi4Ti3O12. As the annealing temperature increases from 600 to 750 deg. C, uniform and crack-free films, better crystallinity and ferroelectric properties can be obtained, but the pyrochlore phase in BTN-BIT films annealed over 800 deg. C would impair the ferroelectric properties. With the increase of O2 flow rate from 0.5 to 1.5 L/min, both remanent polarization P r and coercive electric field E C increase, which are mainly attributed to reduction of the vacanvies of Bi and oxide ions in the films. Natural-superlattice-structured BTN-BIT thin films having 2-1 superlattice annealed at 750 deg. C in O2 ambient with a flow rate of 1.5 L/min exhibit superior ferroelectric properties of P r = 23.5 μC/cm2 and E C = 135 kV/cm