Pyroelectric characteristics of thin PbTiO3 and la-modified PbTiO3 films on platinum films for infrared sensors

Abstract: In this work, we grew lead titanate (PbTiO₃) and La-modified PbTiO₃ thin films on platinized silicon (Si(100)) substrates under controlled substrate temperature and ambient by a modified jet-vapor deposition (JVD) process described in this paper. The x-ray diffraction patterns obtained from these films showed a single-phase perovskite structure. We examined locally homogeneity and thickness of these films through the comparative use of laser Raman spectroscopy. We also collected Raman and x-ray data on pure PbTiO₃, as well as prepared lead zirconate titanate (PZT) (54/46), and PZT (50/50) films using the JVD process. This paper discusses the temperature variations of the pyroelectric and dielectric properties of three compositions of La-modified PbTiO₃ films containing 5.2% to 15% of La, respectively, with a view toward studying the effect of La in place of Pb on these electrical properties. We detected significant pyroelectric currents on all three La-modified PbTiO₃ films before performing poling treatments, and observed pyroelectric coefficeints as high as 84 nC/cm²·°C in the poled La-doped PbTiO₃ films containing 5.2% La. The pyroelectric coefficient and dielectric constant varied significantly with La content. We compared the calculated figures of merit, which were based on the measured physical properties, with pure PbTiO₃ as well as PZT and lead lanthanide zirconate titanate (PLZT) films. These properties just described illustrate that these films would be suitable for IR detectors.