Effects of Membrane Thickness on the Pyroelectric Properties of LiTaO 3 Thin Film IR Detectors

High-performance pyroelectric infrared (IR) detectors have been fabricated using lithium tantalite (LiTaO 3 ) thin films deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by the diol-based sol–gel method. The thermal isolation of detecting elements was achieved by anisotropic wet etching of the back of the silicon substrate. In order to reduce the thermal mass and thermal time constant of the detector, the sensing element was fabricated on a thin membrane. The effects of membrane thickness on the response of pyroelectric IR detectors were studied by changing the membrane thickness (20–350 µm). As the membrane thickness decreased, the voltage responsivity ( R v ) increased from 4300 up to 8398 V/W, and the specific detectivity ( D * ) also increased from 1.2×10 8 to 2.7×10 8 cm·Hz 1/2 /W. Experimental results reveal that the thermally isolated detectors with membrane thickness of 20 µm exhibit excellent sensitivity.