Abstract
Abstract
Lead-free Aurivillius ferroelectric materials have attracted considerable interest for high-temperature piezoelectric devices, non-volatile memories, and energy harvesting applications owing to their excellent thermal stability and environmental compatibility. Among these materials, CaBi₄Ti₄O₁₅ (CBT) exhibits promising ferroelectric properties; however, its functional performance is strongly influenced by deposition conditions and defect chemistry. In this study, 4 mol% cobalt-doped CaBi₄Ti₄O₁₅ (CBT-Co) thin films were deposited on Pt(111)/Ti/SiO₂/Si substrates by pulsed laser deposition (PLD) to investigate the influence of substrate temperature (600 and 700°C) and oxygen partial pressure (0.01, 0.05, and 0.10 mbar) on their structural, morphological, ferroelectric, piezoelectric, and electrical properties. The deposited films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), piezoresponse force microscopy (PFM), polarization–electric field (P–E) hysteresis measurements, and current–voltage (I–V) analysis. The results demonstrate that deposition conditions significantly affect crystallinity, grain morphology, domain switching behavior, leakage current, and piezoelectric response. The film deposited at 600°C and 0.10 mbar exhibited the best overall ferroelectric performance, showing a remanent polarization of 6.17 µC cm⁻² and a coercive field of 148.8 kV cm⁻¹ at an applied voltage of 20 V, together with well-developed ferroelectric domains and improved polarization switching. In contrast, films deposited at higher substrate temperature exhibited larger coercive fields, indicating stronger domain pinning associated with microstructural evolution and oxygen-vacancy-related defects. The optimized deposition conditions also resulted in reduced leakage current and enhanced effective piezoelectric response, confirming the strong correlation between processing parameters and functional properties. These findings demonstrate that careful control of substrate temperature and oxygen partial pressure is crucial for tailoring the microstructure and enhancing the ferroelectric and piezoelectric performance of Co-doped CBT thin films. The present study provides valuable insights into the processing–structure–property relationships of Aurivillius thin films and offers an effective strategy for developing lead-free ferroelectric materials for advanced electronic and electromechanical applications.