To investigate the influence of small amounts of impurities on the initial oxidation of copper, copper oxidation was carried out at 400 and 800 degrees C in 0.1 MPa oxygen atmosphere by using 99.5% (2 N) and 99.9999% (6 N) pure specimens. Oxidation of 6 N copper at 400 degrees C for 60 s showed that the number density of Cu2O oxide islands beneath the thin CuO layer varied with the face of copper crystals, and the nucleation of Cu2O occurred preferentially at grain boundaries. At an elevated temperature of 800 degrees C, nucleation of Cu2O oxide islands beneath the thin CuO layer occurs faster and uniformly over the surface. In contrast to 6 N copper, initial oxidation of 2 N copper is much hindered at 400 degrees C, but this tendency is interestingly weakened at 800 degrees C. The possible roles of impurity elements in the initial oxidation were discussed. The nonmetallic elements of Se and Te segregated in the vicinity of the surface of 2 N copper during the previous annealing process were concluded to play different roles in initial oxidation at 400 and 800 degrees C by considering their thermodynamic behaviors. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.1943667] All rights reserved.