Non-axis tilted texture and post-annealing imprint effects on the energy storage and ferroelectric properties of polycrystalline Bi₂SiO₅ thin films

Layered-structure Bi₂SiO₅ consists of well-bonded Bi–O and Si–O layers and exhibits low leakage current and excellent anti-fatigue characteristics due to its low density of crystal defects and oxygen vacancies. In this study, we investigated the effect of crystallinity on the energy storage characteristics and ferroelectric properties of polycrystalline Bi₂SiO₅ thin films deposited on (111) Pt/TiO₂/SiO₂/Si substrates. The Bi₂SiO₅ thin films deposited at a high substrate temperature of 650 °C showed a highly c-axis tilted texture, whereas those deposited at a lower substrate temperature of 600 °C exhibited a predominantly non-c-axis tilted texture. Notably, films fabricated under a reduced deposition rate of nearly one-tenth at 600 °C revealed the most pronounced non-c-axis orientation. The as-deposited Bi₂SiO₅ thin films with non-c-axis tilted texture showed a relatively small remanent polarization of ∼6.5 μC/cm² and a relatively high saturation polarization of ∼67.1 μC/cm², resulting in a recoverable energy density of 48.1 J/cm³ with an efficiency of ∼87.8 %. Furthermore, the post-annealed Bi₂SiO₅ thin film exhibited an enhanced ferroelectric hysteresis loop imprinting, achieving a higher recoverable energy density of ∼52.1 J/cm³ and an energy storage efficiency of ∼88.7 %. These outcomes suggest that both crystallographic control and post-annealing imprinting can be effective strategies to improve the energy storage capability of Bi₂SiO₅ films while preserving their favorable leakage and fatigue resistance.