APPLICATION OF REFLECTANCE SPECTROPHOTOMETRY TO THE STUDY OF COPPER(I) OXIDES (CU2O AND CU3O2) ON METALLIC SUBSTRATE

The aim of this study is to characterize the compounds grown on copper during the oxidation at low temperature (T < 523 K) by optical method s: photoluminescence and UV-Visible-NIR diffuse reflectance spectrosco py. Two cuprous oxides Cu2O and Cu3O2 have been studied. The absorptio n of Cu2O films in the range 450-630 nm is mainly due to non-stoichiom etry bands associated with copper and oxygen vacancies. Cu3O2 is chara cterized by an optical band gap greater than that of Cu2O (respectivel y 2.25 and 1.95 eV) and by an intense luminescence emission at 760-780 nm. Cu3O2 may be considered as a gross defect structure of Cu2O (a(Cu 2O) = 0.427 nm, aCu3O2 = 0.431 nm). The experimental approach of the o xidation mechanism reveals that a 423 K Cu2O is the primary product wh ich later on is transformed into Cu3O2. Experimental and calculated op tical absorption curves disclose the nucleation of CuO inside the cupr ous oxides layer for oxidation in the range 473-523 K.