In Situ Transmission Electron Microscopy Study of Conductive Filament Formation in Copper Oxides

The structural and electrical property changes of two types of copper oxides (CuO and Cu2O) under voltage bias are studied with in situ transmission electron microscopy (TEM). The phases of different materials are confirmed with electron diffraction. In both types of oxides, dynamic conductive path formation and dissolution are observed. The decrease in resistance of CuO film is found to be accompanied with the formation of Cu4O3 phase where the electric field strength is highest. We also find that the decrease in resistivity of Cu2O film is more extensive and occurs in an area depending on the level of current compliance. The physical mechanisms responsible for the observations and their implications for the formation of conducting regions in copper oxide-based memristors are discussed.