Metal-ferroelectric-insulator-semiconductor (MFIS) capacitor with a BiFeO3 ferroelectric film and a Ba0.5Sr0.5TiO3 buffer layer on a silicon substrate was fabricated and characterized. BiFeO3/Si was studied for comparison. The Ba0.5Sr0.5TiO3/Si structure shows a negligible capacitance-voltage curve and a lower leakage current density of less than 10-7 A/cm2 at 10 V. The maximum memory window of BiFeO3/Si is only 0.38 V due to the severe charge injection. In contrast, a larger memory window of 1.93 V is found for BiFeO3/(Ba0.5Sr0.5)TiO3/Si due to the reduced leakage current by using the (Ba0.5Sr0.5)TiO3 buffer layer. Compared with BiFeO3/Si, the BiFeO3/(Ba0.5Sr0.5)TiO3/Si sample shows a smaller relative dielectric constant of 77.6 and a lower dissipation factor of 0.015 at a frequency of 100 kHz.

Keywords: Ferroelectric, Thin films, BiFeO3.