Abnormal Resistance Switching Behaviors of NiO Thin Films: Possible   Occurrence of Simultaneous Formation and Rupture of Conducting Channels
  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. 
Chunli Liu, S. C. Chae, S. H. Chang, S. B. Lee, T. W. Noh, J. S. Lee,   B. Kahng, D.-W. Kim, C. U. Jung, S. Seo and Seung-Eo...