Unraveling the resistive switching effect in ZnO/0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 heterostructures

This work reports the effect of partial oxygen pressure, used in the deposition of the ZnO layer, on the band alignment at ZnO − 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (0.5BZT-0.5BCT) interface and on the resistive switching (RS) behavior of pulsed laser deposited ZnO/0.5BZT-0.5BCT heterostructures. X-ray photoelectron spectroscopy (XPS) has been employed to measure the valence band offset and the conduction band offset of the ZnO/0.5BZT-0.5BCT heterojunctions. The valence and conduction band offsets of the ZnO/0.5BZT-0.5BCT heterostucture with ZnO deposited at 10−2 mbar of partial oxygen pressure were found to be 0.27 and 0.80 eV, respectively. The RS effect in heterostructures is explained on the base of the charge coupling between the switchable polarization of ferroelectric layer and the non-switchable polarization of semiconductor layer. The heterostructure with ZnO deposited at 10−2 mbar of partial oxygen pressure displays optimum RS characteristics, with a switching ratio ≥ 104 and excellent retention and endurance characteristics. The optimum RS characteristics are attributed to a good interface quality with enough carrier concentration in ZnO, as evidenced by XPS.This work was supported by: (i) Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013 and (ii) Project Norte-070124-FEDER-000070 Nanomateriais Multifuncionais. The author J.P.B.S. is grateful for financial support through the FCT Grant SFRH/BPD/92896/2013. The authors acknowledge the CERIC-ERIC Consortium for access to experimental facilities and financial support under proposal 20157018 and the contribution of the COST Action MP1308-TO-BE. The authors would also like to acknowledge P. B. Tavares, from Centro de Química da Universidade de Trás-os-Montes e Alto Douro, for the supply of the 0.5BZT-0.5BCT PLD target and Engineer José Santos for technical support at Thin Films Laboratory