Preparation and characterization of Ba1−xSrxTiO3 thin films for uncooled infrared focal plane arrays

(Ba1−xSrx)TiO3 (BST) thin films with different compositions have been prepared on Pt/Ti/SiO2/Si substrates by an improved sol–gel technique. DTA–TGA, XRD and SEM are employed to analyze the thermolysis process of BST gel. The dielectric and ferroelectric properties of BST thin films were measured. The results show that the films exhibit pure perovskite phase through rapid thermal anneal (RTA) above 650 °C and their grain size is about 50–100 nm. The dielectric constants of BT, BST5, BST10 and BST15 are 320, 375, 400 and 425, respectively, at 25 °C and 10 kHz. Their loss tangents are 0.035, 0.041, 0.024 and 0.01, respectively. The remnant polarization, Pr, and coercive field, Ec, of BST10 thin film are 2.5 μC cm−2 and 50 kV cm−1, respectively, and the maximal pyroelectric coefficient reaches 12×10−8 C cm−2 K−1 at 35 °C. BST15 thin film is the advanced candidate material for uncooled infrared focal plane arrays (UFPAs) applied at near ambient temperature.