Pyroelectric properties and application to infrared sensors of PbTiO3, PbLaTiO3and PbZrTiO3ferroelectric thin films

Abstract

Highly c-axis oriented PbTiO₃ and Pb_1−xLa_xTi_1−x/4O₃(PLT), and PbZr_xTi_1−xO₃(PZT) thin films were successfully grown with good epitaxy on MgO single crystal and (100)-oriented Pt thin films by rfmagnetron sputtering method. It was found that the thin films have remarkably large pyroelectric effect and high figures of merit for infrared sensors without a poling treatment. The PLT thin films with x = 0.1 have high pyroelectric coefficient γ of 6.5 × 10⁻⁸ C/cm² K and relatively low dielectric constant ε _r of 200. High performance pyroelectric infrared sensors (single element and linear array) were fabricated by using the PLT thin films, the new structures and device processes. The single element sensors have remarkably high D^* (500, 25, 1) of 5 × 10⁸ cmHz^1/2/W and very fast response. Another type of single element sensors with high sensitivity at low frequency can be also offered. The linear array sensors with reticulated PLT films (64 elements, 5 elements/mm) have a small cross talk of 3% at 100 Hz. A remarkably high D^* (500, 100, 1) of 6.0 × 10⁸ cmHz^1/2/W was attained. The nonreticulated array sensors with 10 elements/mm and 128 elements have a high D^* of 1.5 × 10⁸ cmHz^1/2/W.