Highly stable resistive switching on monocrystalline ZnO.

We report on the achievement of planar memristive devices on monocrystalline ZnO substrates using Ti/Al and Pt/Au contacts with dimensions of 100 x 100 microm(2) and spacings of approximately 60 microm. Effects of both thermal and electro-forming processes on the switching characteristics are investigated. It is observed that the thermally formed devices exhibit an extremely large R(OFF)/R(ON) value of approximately 20 000. The electrically formed devices, on the other hand, demonstrate an exceptional switching stability, with R(OFF)/R(ON) variations of < 2% for durations of over 10(5) s and more than 1800 switching cycles. The dependence of the switching characteristics on the formation processes, as well as the metal electrodes, could be explained by an oxygen vacancy formation/annihilation and migration model.