THE OXIDATION OF CU PARTICLES SUPPORTED ON OXIDIZED SI(100) AS STUDIED BY NUCLEAR-REACTION ANALYSIS AND ELLIPSOMETRY

The oxidation of Cu particles supported on oxidised Si(100) by molecul ar oxygen was investigated by means of ellipsometry and Nuclear Reacti on Analysis. Stepwise oxidation of a sample containing 15 nm Cu partic les at 473 K and 0.1 Pa showed that the sample was eventually oxidised to CuO0.74+/-0.08, which is very close to CuO0.67, known from the lit erature. The ellipsometric parameter delta Delta followed a highly non -linear curve upon oxygen exposure, exhibiting a maximum during oxidat ion, but stabilising when the CuO0.74+/-0.08 oxide composition was rea ched. The oxide stoichiometry was less than Cu2O at the maximum of the delta Delta-curve, indicating that the CuO0.67-phase nucleated in the sample before the formation of Cu2O had been completed, During surfac e oxidation, the sensitivity of delta Delta to the amount of oxygen wa s similar to that of copper single crystals. The sensitivity of delta Delta to oxygen increased significantly while samples were oxidised to Cu2O and further: it was almost three times larger than the sensitivi ty of delta Delta to oxygen for surface oxidation.