Ferroelectric properties of (Bi3.15Nd0.85)Ti3O12with decreasing film thickness

Film texture and ferroelectric behaviors of (Bi3.15Nd0.85)Ti3O12 (BNdT) of layered-perovskite structure deposited on Pt/TiO2/Si substrate are dependent on the film thickness. When the film thickness is reduced from ∼240 to ∼120 nm, BNdT grains evolve from a rod-like morphology to a spherical morphology, accompanied by a decrease in average grain size. At the same time, P-E hysteresis transforms from a square-shaped hysteresis loop (2Pr ∼24.1 μC/cm2 at 240 nm) to a relative slimmer hysteresis loop (with a lower 2Pr = 19.8 μC/cm2 at 120 nm). The nonvolatile polarization (Δ P) shows a maximum at the film thickness of 160 nm, where Δ P was measured to be 14.7 μC/cm2 and 6.8 μC/cm2 at 5 V and 3 V, respectively. A small amount of excess bismuth in the film thickness of 130 nm, introduced by co-sputtering, can lead to a much enhanced remanent polarization (2Pr of 21.3 μC/cm2 at 5 V and 15.2 μC/cm2at 3 V), which is promising for low voltage FRAM applications.