Influence of Different Substrates on the Detectivity of Pyroelectric Sensors

Nanosized lead titanate doped with calcium and lanthanum (PCLT) powder obtained by the sol-gel method was homogeneously mixed with vinylidene fluoride-trifluoroethylene [P(VDF-TrFE)] to form nanocomposites. Several pyroelectric sensors were prepared on porous silicon dioxide, on poly(ethylene terephthalate) (PET) film and on bulk silicon substrates, respectively. The nanocomposite PCLT/P(VDF-TrFE) sensing film was deposited by spin-coating and Ni-Cr film was deposited as the top electrode and absorption layer. Experimental results showed that the substrate of the pyroelectric sensor could significantly affect the specific detectivity. The porous silicon dioxide and PET plastic film substrates could effectively decrease the thermal conductivity and the thermal fluctuation noise of the pyroelectric element, increase the voltage responsivity and the specific detectivity. The results indicated that the specific detectivity of PCLT/P(VDF-TrFE) pyroelectric sensors based on porous silicon dioxide and PET plastic film substrates reached 4.2E6 and 3.4E7 cmHz^1/2 W⁻¹ respectively, which is about 1-2 orders of magnitude higher than that of the sensors formed under the same condition on the bulk silicon substrate.