Two-Dimensional Pyroelectric Material with Heat-Transfer Modulation

Abstract

Strontium barium niobate Sr_xBa_1 – xNb₂O₆ films, grown by plasma sputtering on layers of indium tin oxide and platinum on silicon and sapphire substrates, are investigated. Such materials are used in pyroelectric electro-optical converters of a new generation. A two orders of magnitude higher sensitivity to temperature change is detected in some of the investigated films compared to crystalline Sr_xBa_1 – xNb₂O₆, the pyroelectric coefficient of which is γ ~ 6 × 10⁻⁴ C/m² K. The observed phenomenon is explained by the emergence of mobile elements in the “substrate–bottom electrode–ferroelectric–top electrode” system when the top electrode is detached from the ferroelectric. Leakage currents are unevenly distributed across the surface, often concentrated at local points or areas that can be considered one dimensional. It is known that the boundaries of ferroelectric domain walls exhibit abnormally high conductivity. In contrast to a tightly pressed electrode, where charge leakage may occur through it, in this structure, all the charge resulting from the change in spontaneous polarization during heating is transferred to the external circuit. This process occurs because the leakage-current points are local, and in the absence of a pressed electrode, the current flows along the surface.