The satellite peaks are also produced by Cu2+. In Fig. 5(c), the O 1s core-level spectrum is broad, and two O 1s peaks can be resolved by using curve-fitting procedure. The peak observed at 529 is in an agreement with O2 in CuO, while peak at 531.2 eV is attributed to O adsorbed on the surface of rectangular shaped structure of CuO. Thus XPS result indicates that the sample is composed of CuO. In Fig. 6, the weight loss was observed in the region between 320 and 400 8C where reduction of CuO might occur