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Thickness dependence of piezoelectric properties of BiFeO3 films fabricated using rf magnetron sputtering system

The piezoelectric property of BiFeO3 films prepared on a (100) LaNiO3/Si(100) substrate using an rf magnetron sputtering system was investigated for their applications in MEMS vibration energy harvesters. The X-ray diffraction profiles indicate that (100)-oriented BiFeO3 films with thicknesses from 450 to 1750 nm were obtained at a deposition temperature of 510 °C. All the films showed well-defined ferroelectric hysteresis loops at room temperature. The thickness dependence of crystallinity and electrical properties indicated that the films have a bottom layer with a high defect density. The e31,f piezoelectric coefficient and electromechanical coupling factor () increase with increasing film thickness and reach −3.2 C/m2 and 3.3%, respectively, at a thickness of 1750 nm, which is considered to be caused by the decrease in defect density.