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Parameters controlling the design of a pyroelectric PVDF matrix arrayVui V. Pham, Daniel Esteve, Essaid Bousbiat, Jean Farre, Rene Leguerre, Jean SimonneLaboratoire d'Automatique et d'Analyse des Systemes du C.N.R.S.7, ay. du Colonel Roche, 31077 Toulouse cedex, FranceAbstractPVDF, mostly investigated for its piezoelectric properties has been also demonstratedas a promising candidate for pyroelectric detection ; the challenge is to assess how far itsperformance can be brought to set the chance of development of PVDF infrared detectors tocivilian applications with regard to other conventional pyroelectrics.We have therefore elaborated discrete elements, linear arrays and test structures on9 to 40 4m thick materials to check the best conditions to be fulfilled in order to designa bidimensional array, with 8 x 8 elements to begin with.The poling process carried out on a biaxially strdched material with a slowly increa-sing a.c. electric field at room tempe5ature (the Bauer's method) insures the largestremanent polarization (around 10 4C /cm ) and its stability with time. Sensibility of freelymounted detectors decreases as an hyperbolic function of the thickness, while the thermalcut off time constant increases up to a limit reached at 25 µm. Influence of the pixel areaand spacing between cells on cross talk is also investigated on a multi -units array.Finally, design of a matrix is proposed.IntroductionAs infrared detection and imaging are promised to make a real breakthrough in the90's, thermal detection is to date considered as a true alternative way to quantum detec-tion in specific applications where ultimate detectivity is not required, like in driveand security in automotive, watching, alarm, medical controls and even in certain militaryapplications.In the same way ub MCT (Mercury Cadmium Telluride) is in competition with Silicides /Siin the 3 -5 4m range in cooled IR -FPA (Infra Red Focal Plane Array), PVDF (PolyvinylideneFluoride) is emerging in pyroelectrics, against ceramics, even if today the best perfor-mances of a 32 x 32 FPA have been achieved with a material of the _PZLT _lceramic familyEven though the pyroelectric coefficient of PVDF |
