Ferroelectric tunnel junctions (FTJs) exhibit resistance switching associated with the reversal of the ferroelectric polarization in the barrier material. We have explored the influence of the top electrode materials (W, Co, Ni, Ir) on the electronic band profile in FTJs based on BiFeO3 barriers. Large variations of the transport properties are observed at room temperature. In particular, the analysis of current vs. voltage curves by a direct tunneling model indicates that the metal/ferroelectric interfacial barrier height increases with the top-electrode work function. While larger metal work functions result in larger OFF/ON ratios, they also produce a large internal electric field which results in large and potentially destructive switching voltages.
Engineering ferroelectric tunnel junctions through potential profile shaping
S. Boyn et al, APL Materials 3, 052503 (2015)