Thickness-dependent microstructural optimization to enhance piezoelectric performance in 0.7Pb(Mg1/3Nb2/3)O₃-0.3PbTiO₃ thin films

The ferroelectric thin film 0.7Pb(Mg1/3Nb2/3)O₃-0.3PbTiO₃ (PMN-PT) shows great promise in microelectronic sensing technologies due to the excellent piezoelectric and dielectric properties. However, the structural and functional evolution of films at the micrometre-scale thickness remains unclear, posing a significant challenge for performance stability and device integration. In this study, PMN-PT films with thicknesses precisely controlled at 0.32, 0.62, 1.07, and 1.29 μm are fabricated via the sol-gel method, and the effects of thickness on surface morphology, crystal orientation, electrical properties, and piezoelectric response are systematically investigated. The results show that with increasing film thickness, the films have higher dielectric frequency stability and insulation. However, the preferred crystal orientation gradually shifts from (100) to (110) with increasing thickness, thereby weakening the polarization response. Notably, the 0.62 μm-thick film achieves the optimal performance balance, exhibiting the strongest piezoelectric response with an effective piezoelectric coefficient d₃₃* of 91 pm/V, highlighting the potential for advanced sensor applications.