Ferroelectric domain structures of PbTiO₃ thin films with imprinted ferroelectric hysteresis loops

Understanding and controlling the domain structures and their stability in ferroelectric thin films is crucial for advancing technologies such as energy storage, memory devices, and sensors. By optimizing domain behavior, it is possible to enhance the performance, efficiency, and reliability of ferroelectric-based systems in these applications. Here, we investigated the imprinted ferroelectric hysteresis loops and the imprinted ferroelectric domain structures of the PbTiO₃ (PTO) multilayer thin films, including the oxygen depletion layer. The PTO multilayer thin films were made of a structure of DPTO/PTO/Pt/glass by PTO and PbTiO_3-δ (DPTO) layers by pulsed laser deposition. When the thickness of the DPTO layer was increased to 0, 5, and 7.5 nm, it was observed that the imprint effects of the ferroelectric hysteresis loops of the PTO multilayer thin films increased significantly. Through the observation of ferroelectric domain structures via Piezoresponse force microscopy, it was confirmed that the imprinted ferroelectric hysteresis loops were favored in terms of free energy in one polarization direction. This emphatically verified the presence of imprinted ferroelectric domain structures. Our study offers new insights into the correlation between the thickness of the oxygen-deficient DPTO layer and the enhancement of imprinted ferroelectric hysteresis loops and domain structures in PbTiO₃ thin films. These findings propose a novel design strategy for optimizing ferroelectric properties to advance practical applications.