Electrochemical analysis of initial oxide layers on copper surface

In this study, coulometric reduction method was adopted to investigate the phase and thickness of surface oxide layer of sputtered copper. The samples subjected to citric acid wash and room temperature storage were investigated. Repeated reduction tests in NaOH solution was also carried out to explore the very early state of the copper surface. According to the reduction potential ranging from -0.62 to 0.65 V, the initial oxide formed in NaOH solution was CuO with the thickness of around 1.1~1.2 nm.