Semiconductor/piezoelectrics hybrid heterostructures with highly effective gate-tunable electrotransport and magnetic behaviors

We report the epitaxial growth of oxygen deficient titanium dioxide thin films on 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) single crystals and realized highly effective in situ electrostatic manipulation of electrotransport and magnetism of TiO_2-δ films via gate voltages. Upon the polarization switching in the PMN-PT, the carrier density of the TiO_2-δ film could be reversibly modified, resulting in a large nonvolatile resistivity modulation by 51% at T = 300 K, approximately 4-12 times larger than that of other transition-metal oxide film/PMN-PT structures. By taking advantage of in situ manipulation of the carrier density via gate voltages, we found that competition between the trap of electrons by the Ti³⁺-V_O pairs and that by the positive polarization charges at the interface results in a significant resistivity relaxation upon the polarization switching, and revealed that magnetization is inversely correlated with the carrier density of the TiO_2-δ film. Such hybrid structures combining materials with dissimilar functionalities may have potential applications in multifunctional devices which can take advantage of the useful and unique properties of both materials.