Physical characteristics and electrical properties of Sr0.8Bi2+xTa2O9 films on Al2O3/Si annealed at high temperature

Bismuth-containing layered perovskite ${\mathrm{Sr}}_{\text{0.8}}{\mathrm{Bi}}_{\text{2+x}}{\mathrm{Ta}}_2{\mathrm{O}}_9$ (SBT) thin films with $\text{x=0–0.8}$ were prepared to investigate annealing temperature effect, especially at high temperature, on physical characteristics and electrical properties of SBT films on ${\mathrm{Al}}_2{\mathrm{O}}_3$ (10 nm)/Si. At 800 °C, the ${\mathrm{Sr}}_{\text{0.8}}{\mathrm{Bi}}_2{\mathrm{Ta}}_{\text{2+x}}{\mathrm{O}}_9/{\mathrm{Al}}_2{\mathrm{O}}_3/\mathrm{Si}$ exhibits ferroelectric mode and the width of memory window decreases with the increase of Bi content that is dependent on the effective coercive field. However, at a higher annealing temperature of 900 °C, a larger ferroelectric memory window was obtained for Bi-rich ${\mathrm{Sr}}_{\text{0.8}}{\mathrm{Bi}}_{\text{2+x}}{\mathrm{Ta}}_2{\mathrm{O}}_9$ $\text{(x=0.4}$ or 0.8) films compared to SBT film $\text{(x=0)}$ that should be related to the reduced leakage current due to the formation of rod-shape grains and amorphous SBT composite layer. The leakage current of ${\mathrm{Sr}}_{\text{0.8}}{\mathrm{Bi}}_{\text{2.4}}{\mathrm{Ta}}_2{\mathrm{O}}_9/{\mathrm{Al}}_2{\mathrm{O}}_3/\mathrm{Si}$ annealed at 900 °C is about ${\text{1.2×10}}^{\text{−9}}\hspace{0.17em}{\mathrm{A/cm}}^2$ that has two orders of magnitude lower than that of 800 °C-annealed SBT films measured at −100 kV/cm. However, the ${\mathrm{Sr}}_{\text{0.8}}{\mathrm{Bi}}_2{\mathrm{Ta}}_2{\mathrm{O}}_9$ $\text{(x=0)}$ film on ${\mathrm{Al}}_2{\mathrm{O}}_3/\mathrm{Si}$ capacitor shows no obvious change with the increase of annealing temperature.