In the study of the characteristics and mechanisms of resistive switching behavior in oxide, most researchers just analyze the point I-V curves or current images/surface potential images after removing the external electric field by conductive Atomic Force Microscopy (c-AFM) combined with Kelvin Probe Force Microscopy (KPFM) (Min Hwan Lee et al, 'Scanning probe based observation of bipolar resistive switching NiO films'). There are few people who study the current image with/without the high external electric field simultaneously.

Does anyone find that with/without the high external electric field, the resistance states are different? I mean, when you apply bias (such as 1V to 10V) to a certain area, you can get a high current image at these regions, which you can make you consider this area to be in a low resitance state. However, when you remove this bias and scan this area with very small bias (0.5V) at a larger area, you may find that there is no current in the area, which is scanned by 10V. What's the mechanism underlying this phenomenon?