Preparation, phase transition diffuseness and ferroelectric fatigue behavior of Ba0.85Sr0.15TiO3 thin film for uncooled infrared focal plane arrays

Ba0.85Sr0.15TiO3 (abbreviated to BST15) thin film has been prepared on Pt/Ti/SiO2/Si3N4/SiO2/Si substrates by novel sol–gel technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and tunneling electron microscopy (TEM), etc are employed to analyze the crystallization process of BST15 film. The ferroelectricity and phase transition diffuseness behavior of virgin and fatigue BST15 film are discussed. The result shows that BST15 film annealed at 700 °C exhibits pure perovskite phase with a random orientation and possess advanced ferroelectricity at room temperature (RT). The dielectric constant, remnant polarization and coercive field of virgin BST15 film are, respectively, 475, 3.7 μC cm−2 and 45 kV cm−1, at 25 °C and 10 kHz. Measured at 50 Hz, Curie point (Tc) of virgin BST15 film is 30° C, at which its maximal pyroelectric coefficient reaches 1.2×10−7 C cm−2 K−1. However, no sharp peak but just the recessive and extended protuberances can be observed in the curves of dielectric constant versus temperature of BST15 film, and this effect is enhanced with the increasing frequency. It means the diffuseness of ferro-to-para phase transition in BST15 film. The nonlinear capacitance and coercive field decrease but the leakage current density increases in fatigue BST15 film. BST15 film is hopeful to be the candidate sensitive material for uncooled infrared focal plane arrays (UFPAs) applied at near RT.