Calcium lead titanate thin films for pyroelectric detector application

Pyroelectric materials show a change in their spontaneous polarization due to the temperature variations. This property makes these materials unique for sensing radiation in the infrared (IR) broad range. Here, we report the deposition and characterization of pyroelectric Calcium Lead Titanate (PCT) thin films for using them to fabricate pyroelectric detectors. PCT films were deposited on both silicon and Si/SiN/Ti/Au substrates at 13 mTorr pressure by 200W Radio Frequency (RF) sputtering in Ar+O₂ environment for four hours. Substrates were kept at variable temperatures starting from 550 ºC up to 800 ºC during the deposition. The PCT films were annealed at 550, 600, 650 and 700 ºC in O₂ environment for 15 minutes. X-ray diffraction (XRD) results confirm the polycrystalline nature of these films. Energy dispersive spectroscopy (EDS) function of scanning electron microscope (SEM) was done to determine the elemental composition of PCT films. Our EDS result reveals the presence of the elements such as Calcium, Lead, Titanium , and Oxygen in the thin films. Moreover, it shows that the films are stoichiometric (Ca0.43Pb0.57)TiO3 (Ca/Ti=0.5, Pb/Ti=0.66). The film thicknesses were measured using a Dektak model XT profilometer which ranges from ~ 250 to 400 nm. The surface morphology obtained from SEM and atomic force microscopy confirms the crack-free nature of our films as well as their smoothness and low surface roughness. Temperature dependence of capacitance, pyroelectric current, and pyroelectric coeeficient were investigated for different PCT films. Our results show that films deposited at 550ºC and 600 ºC demonstrate better quality and larger values of pyroelectric coefficient. On the other hand, the capacitance fabricated on the PCT films at 550 ºC showed the highest value of pyroelectric current and pyroelectric coefficient which are 14 pA and 50 μC/m2K respectively at higher temperature.