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Ferroelectricity in ultrathin asymmetric ferroelectric tunnel junctions: vanishing critical thickness

Using a modified thermodynamic model, the critical thickness of ultrathin asymmetric ferroelectric tunnel junctions (A-FTJs) is investigated considering the effects of size, asymmetric interfaces and electrodes on the stability and magnitude of two spontaneous polarization states. The results illustrate the important behaviour of vanishing critical thickness for one polarization state due to the existence of a built-in electric field induced by the asymmetric electrodes. The critical thickness for another polarization state exists and can be controlled by adjusting the properties of the asymmetric electrodes. Our results also indicate that other properties of the A-FTJ should be tunable with the design of its asymmetric electrodes.