CHARACTERIZATION OF THE INITIAL-STAGES OF COPPER OXIDATION BY OPTICAL-ABSORPTION AND PHOTOLUMINESCENCE

Optical methods are easy to use and give useful informations on oxidat ion products. In the case of copper oxides, layers from several nanome ters up to several micrometers thick can be studied. The following oxi des : Cu(x)O precursor of Cu2O, Cu2O, Cu3O2 and CuO are characterized by UV-Vis-NIR diffuse reflectance spectroscopy. The defects in cuprous oxides may be identified by photoluminescence spectra. The oxide form ed at 423 K for long oxidation times is Cu3O2. In the 473-573 K temper ature range, the outer layer is a mixture of CuO and copper (1) oxides and periodic changes in the composition of the layer are observed in the early stages of oxidation. The experimental data observed at 573 K indicate that the oxidation involves a fast process Of Cu to Cu3O2 (2 Cu + 1/2 O2 --> Cu2O and 3 Cu2O + 1/2 O2 --> 2 Cu3O2) and a slow proc ess for the formation of CuO. For copper oxidation at T greater-than-o r-equal-to 673 K, the corrosion layer is a multiphase and multilayer s tructure : CuO/Cu3O2/Cu2O/Cu.