A copper oxide (CuxO) layer was formed by applying plasma oxidization on a copper film grown on a Si substrate. Pt deposited on this CuxO layer then function as the top electrode to form a Pt/CuxO/Cu structure. A device created with this structure exhibited a forming-free bipolar resistive switching property. Conductive atom force microscope (C-AFM) was employed to investigate the nanoscale electrical properties of the device. Based on I-V curve analysis, it was found that the Poole-Frankel and conducting filaments models were suitable for the present device. C-AFM analysis for the sample indicated that the random formation/rupture of conducting paths in the CuxO layer may play a key role for the device instability in high resistance state. (C) 2013 Elsevier B.V. All rights reserved.