Figure 3. Statistic results of current reading at +2 V and −2 V after process (1) to (4), respectively when the current compliance was set at 10 nA.

Both states can be kept after the power is shut down while the resistance of the ZnO nanoisland depends on both the process that the nanoisland undergoes and the polarity of the reading voltage. This suggests that the observed threshold-like I–V characteristics is a bistable resistive switching.