Characterization of Oxide Layers on Technical Copper Material Using Ultraviolet Visible (UV-Vis) Spectroscopy as a Rapid On-Line Analysis Tool.

An ultraviolet visible (UV-Vis) spectroscopy method was developed that can quantitatively characterize a technical copper surface to determine oxide layers and organic impurities. The oxide layers were produced by a heating step at 175 ℃ for four different times (range = 1-10 min). Partial least squares (PLS) regression was used to establish a relation between the UV-Vis spectra and film thickness measurements using Auger electron spectroscopy depth profiles. The validation accuracy of the regression is in the range of approximately 2.3 nm. The prediction model allowed obtaining an estimation of the oxide layer thickness with an absolute error of 2.9 nm. Alternatively, already known methods cannot be used because of the high roughness of the technical copper surfaces. An integrating sphere is used to measure the diffuse reflectance of these surfaces, providing an average over all angles of illumination and observation.