Pyroelectric Properties of La-modified Lead Titanate Thin Film Detectors

High-performance pyroelectric infrared (IR) detectors have been fabricated without the back side etching process using La-modified lead titanate (PLT) thin films. PLT thin films were deposited on (111)-oriented Pt thin film on SiO2/Si(100) substrates by a diol-based sol-gel process. The randomly oriented PLT thin film exhibits a relatively small dielectric constant and a large pyroelectric coefficient without poling treatment. The pyroelectric characteristics of point detectors with various La contents as a function of modulation frequency are compared. It was found that the PLT(10) detector has a large voltage responsivity of 3330 (V/W) at 20 Hz. The specific detectivity (D *) at 100 Hz is 6.2×107 cmHz1/2/W. The results showed that Pb1-x La x Ti1-x/4O3 thin film with x=0.10 [PLT(10)] was most suitable for use as a pyroelectric IR detector.