Exploration of highly enhanced performance and resistive switching mechanism in hafnium doping ZnO memristive device

1 x 1 mu m(2) via hole structure ZnO-based resistive random access memory cells are fabricated and the resistive switching behavior is investigated. It can be found that with 5.7% hafnium-doped ZnO film, the memory cell shows remarkable 10(8) pulse endurance. An ON/OFF resistance ratio of at least two orders of magnitude is achieved and the resistive states can remain stable up to 10(4) s. In contrast, a Pt/ZnO/TiN control device presents an unstable resistive switching characteristic and endurance degradation. Compared with pure ZnO film, Hf-doped ZnO film has a relatively smoother surface and larger band gap. X-ray photoelectron spectroscopy analysis indicates that the Hf-doped element induces more non-lattice oxygen ions in the ZnO switching layer. We deduce that the conductive filament forms/ruptures in a fixed path along the Hf atoms. Based on I-V curve fitting and temperature-dependent current measurements, the Pt/Hf:ZnO/TiN device is demonstrated as a Schottky conduction mechanism, which shows reasonable agreement with the possible resistive switching mechanism in the hafnium-doped ZnO memristive device.