Ferroelectric materials and devices in infrared detection and imaging

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Abstract
The use of ferroelectric materials for infrared detection and thermal imaging is an established technology. For example, small pyroelectric detector arrays form the basis of the infrared burglar and intruder alarm industry, and the pyroelectric vidicon camera tube has been successfully exploited for thermal imaging in a wide range of industrial and civil applications. Interest in the ferroelectric materials for infrared devices has continued to grow, based on the ambient temperature operation and the potential for low power and cheap detector technologies. In the recent programmes, the attention has turned to research on the new technologies needed to fabricate large hybrid arrays of ferroelectric detectors interfaced with silicon readout ICs. The key items in the hybrid device for the research programmes are firstly the ferroelectric material for the detector wafer, secondly the design of the silicon readout circuit and thirdly the solder bump, flip-chip technology used to fabricate the hybrid. This paper concentrates on the ferroelectric materials and their performance merit. The materials with a good balance of merit between performance and ease of fabrication are the perovskite ceramics. These may be used in two possible modes. The first is the conventional pyroelectric, but a second alternative mode is to utilize the dielectric peak close to the transition temperature in a dielectric bolometer device, with an applied field across the ceramic element. Materials for the two modes will be different, but can be compared through the general pyroelectric coefficient, p = (dD/dT)E. Factors which apply in both modes to determine the material merit will be discussed.

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