Forming Process Investigation of $\hbox{Cu}_{x} \hbox{O}$ Memory Films

The forming process, which is the first transition from fresh state to low resistance state, was investigated in Cu
_x
O memory films prepared by plasma-induced oxidation. X-ray photoelectron spectroscopy investigation of surface chemical bonds of Cu
_x
O films and Auger electron spectroscopy depth spectra show that the formation of a highly resistive CuO layer on the Cu
_x
O surface is the main reason for the requirement of a large forming voltage. After selectively deoxidizing the CuO into Cu
₂
O, the need for the "forming" process disappears.