Huge gain in pyroelectric energy conversion through epitaxy for integrated self-powered nanodevices
Résumé
Polycrystalline (textured) and epitaxial 500 nm thick Pb(Zr0.52Ti0.48)O3 (PZT) layers have been monolithically integrated in metal-insulator-metal structure on silicon in order to compare their pyroelectric properties, both statically (under stabilized temperatures) and dynamically (when submitted to temperature transient as a pyroelectric device should work). The films have roughly the same out-of-plane orientation, and thus a similar out-of-plane remnant ferroelectric polarization around 12 μC/cm2. Whereas their static pyroelectric coefficients are similar (around −470 μC m−2 K−1), the dynamic pyroelectric coefficient of the epitaxial layer is about one order of magnitude larger than that of the polycrystalline layer (−230 vs −30 μC m−2 K−1). This causes an important difference on the densities of converted pyroelectric energy by almost two orders of magnitude (1 vs 1.5 10−2 mJ/cm3 per cycle for temperature variations of ∼6 K). This difference is explained here by the counterbalanced extrinsic pyroelectric contribution arising from the domain walls motion in the dynamical measurements. Extrinsic pyroelectric contribution appears almost twice larger on polycrystalline layer than on epitaxial layer (+430 vs +250 μC m−2 K−1). These results are crucial for further design of advanced integrated pyroelectric-based nanodevices.
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