Structural, ferroelectric and dielectric properties of Na_0.5Bi_0.5(Ti_0.98Fe_0.02)O₃ thin films on different substrates

Na_0.5Bi_0.5(Ti_0.98Fe_0.02)O₃ (NBTFe) thin films have been prepared on monocrystalline Si, Al-doped ZnO/glass and Pt/TiO₂/SiO₂/Si substrates by metal organic decomposition combined with sequential layer annealing. The structure, leakage current, ferroelectric and dielectric properties of NBTFe thin films are very sensitive to the using substrates. The NBTFe on Si exhibits a competitive growth mode with various oriented crystallites at different annealing temperature. At 550 °C, the NBTFe on all the substrates crystallize into the pure rhombohedral perovskite structure with an obvious difference in orientation. The electrical measurements were conducted on metal–ferroelectric–semiconductor and metal–ferroelectric–metal capacitors. The NBTFe film on Si exhibits the capacitance–voltage curve with a maximum memory window of 2 V at the applied voltage of ±6 V originated from the ferroelectric polarization. The NBTFe film on Al-doped ZnO/glass shows a round polarization–electric field hysteresis loop due to the large contribution from the leakage current. In contrast, a large remanent polarization (P _r ) of 18 μC/cm² for NBTFe deposited on Pt/TiO₂/SiO₂/Si can be obtained. Also, the NBTFe thin film on Pt/TiO₂/SiO₂/Si shows a high ε _r of 313 and low tan δ of 0.1 at 100 kHz.