Optimization and experimental verification of a pyroelectric bimorph radiation detector

Theoretical and experimental studies were made of pyroelectric bimorph radiation detectors. The bimorphs consisted of two thin layers on a substrate, the upper one having a large pyroelectric coefficient and a large permittivity, and the lower one having a smaller pyroelectric coefficient and a smaller permittivity. The incident radiation is absorbed in the electrode on the upper layer. If the radiation is modulated at a sufficiently high frequency, the thermal waves which are produced will penetrate the upper layer completely but only penetrate the lower layer partially, so that the effective pyroelectric coefficient will be dominated by that of the upper layer. However, the capacitance of the bimorph will be the series combination of the two layers and will be lower than that of either of them. This gives a voltage responsivity that is larger than that of either of the two layers used alone. The analysis was verified experimentally using a PLZT (12/30/70)/PZT (30/70) bimorph. The design of a PLZT (8/35/65)/LiTaO/sub 3/ bimorph was simulated. The calculated voltage responsivity was more than 100 times that of a PLZT (8/35/65) monomorph having the same thickness.