Surface-micromachined PbTiO3 pyroelectric detectors

Abstract

Lead titanate (PbTiO₃) thin‐film pyroelectric infrared detectors have been fabricated on polycrystalline silicon micromechanical membranes. Pyroelectric PbTiO₃ thin films of thickness ranging from 0.2 to 0.6 μm were prepared by sol‐gel spin casting techniques and deposited on 1.0‐μm‐thick polycrystalline silicon membranes suspended 1.0 μm above the surface of a silicon wafer. This composite structure offers high sensitivity and low thermal mass. The measured pyroelectric coefficient for 0.36‐μm‐thick PbTiO₃ films is 90 nC/cm² K. The measured blackbody voltage responsivity for a pyroelectric element with an active area of 7×10⁻⁴ cm² at 297 K and a chopping frequency of 50 Hz is 4.2×10⁴ V/W. The measured normalized detectivity D* at 297 K and 50 Hz is 1.0×10⁹ cm Hz^1/2/W.