Sol-gel derived pyroelectric barium strontium titanate thin films for infrared detector applications

Ba_0.8Sr_0.2TiO₃ thin films were prepared by a sol-gel technique using a highly diluted precursor solution. A columnar structure with grain size close to 200 nm was obtained with layer-by-layer homoepitaxy due to a very small thickness of individual layer. A remnant polarization of 3.5 μC/cm² and a coercive field of 83 kV/cm were measured. The remnant polarization of the films decreases with the temperature increasing. Especially from 7 to 40 °C, the remnant polarization decreased rapidly, which results in a large pyroelectric coefficient. The infrared response, measured using a 500 K chopped blackbody and a voltage amplifier with an amplification of 6000 at room temperature, exhibits a typical pyroelectric response waveform. The Ba_0.8Sr_0.2TiO₃ thin-film-capacitor with a top electrode area of 3.4×10^-3 cm² exhibits an output voltage of 280 mV at a chopping frequency of 10 Hz.