Depolarization modulated tunneling in ferroelectric tunnel junctions

Abstract

We investigate charge tunneling in asymmetric junctions comprising a ferroelectric barrier BaTiO3 with a common La0.7Sr0.3MnO3 bottom electrode and various metallic top electrodes. Quantitative analysis of tunneling electroresistance within a direct tunneling framework reveals that the net change in average barrier potential upon polarization reversal scales with the depolarizing electrostatic field, governed by screening asymmetry at the ferroelectric–electrode interfaces. The observed electrode-dependent tunneling electroresistance is thus primarily controlled by the potential barrier height at the top interface. Our results, supported by theoretical considerations and experimentally determined lower bounds to the depolarization field, emphasize the key role of interface electrostatics in ferroelectric tunneling transport.