  We report the detailed current-voltage (I-V) characteristics of resistance
switching in NiO thin films. In unipolar resistance switching, it is commonly
believed that conducting filaments will rupture when NiO changes from a low
resistance to a high resistance state. However, we found that this resistance
switching can sometimes show abnormal behavior during voltage- and
current-driven I-V measurements. We used the random circuit breaker network
model to explain how abnormal switching behaviors could occur. We found that
this resistance change can occur via a series of avalanche processes, where
conducting filaments could be formed as well as ruptured.
