  In this study, direct-current reactive sputtered ZnO and ZnO1-x based thin
film (30 nm and 300 nm in thickness) memristor devices were produced and the
effects of oxygen vacancies and thickness on the memristive characteristics
were investigated. The oxygen deficiency of the ZnO1-x structure was confirmed
by SIMS analyses. The memristive characteristics of both the ZnO and ZnO1-x
devices were determined by time dependent current-voltage (I-V-t) measurements.
The distinctive pinched hysteresis I-V loops of memristors were observed in all
the fabricated devices. The typical homogeneous interface and filamentary types
of memristive behaviors were compared. In addition, conduction mechanisms,
on/off ratios and the compliance current were analyzed. The 30 nm ZnO based
devices with native oxygen vacancies showed the best on/off ratio. All of the
devices exhibited dominant Schottky emissions and weaker Poole-Frenkel
conduction mechanisms. Results suggested that the oxygen deficiency was
responsible for the Schottky emission mechanism. Moreover, the compliance
currents of the devices were related to the decreasing power consumption as the
oxygen vacancies increased.

Applied Physics;Mesoscale and Nanoscale Physics