Thermally optimized linear pyroelectric array

Abstract

The aim of this research project was to develop a linear 128 element pyroelectric array deposited on a polyimide film substrate. Polyimide has a substantially lower thermal conductivity than silicon, and therefore it is expected that a pyroelectric sensor array on polyimide can achieve a good performance without the use of complex procedures like surface micromachining. A possible drawback of a highly flexible material as the carrier for the pyroelectric elements may be an increased sensitivity to microphony. Therefore, we will make use of a composite pyroelectric with compensated piezoelectric response. Preliminary work has shown that piezoelectrically compensated composite can be fabricated using lead titanate nanoparticles in P(VDF-TrFE) with a ceramic volume fraction of about 30%. This material can be fabricated in the form of a 0-3 composite by hot pressing. The sensor array is prepared by directly hot pressing 40um thick PT/P(VDF-TrFE) film on the electrode structure on the polyimide carrier. This film is then polarized to achieve piezoelectric compensation. Moreover, the pyroelectric, piezoelectric and dielectric properties of the pyroelectric material have also been measured in order to characterize its ferroelectric properties. To compare the sensor performance and the sensitivity to microphony with a polymer sensor, we have fabricated a single - element sensor with both PT/P(VDF-TrFE) and P(VDF-TrFE) elements located at opposite sides of a polyimide membrane. The piezoelectric response of the two elements to vibration has been measured. The current sensitivity and the crosstalk of a selected pixel of the array are also characterized.