The oxidation of Cu particles supported on oxidised Si(100) as studied by nuclear reaction analysis and ellipsometry

The oxidation of Cu particles supported on oxidised Si(100) by molecular oxygen was investigated by means of ellipsometry and Nuclear Reaction Analysis. Stepwise oxidation of a sample containing 15 nm Cu particles 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 literature. The ellipsometric parameter δΔ followed a highly non-linear curve upon oxygen exposure, exhibiting a maximum during oxidation, but stabilising when the CuO0.74 ± 0.08 oxide composition was reached. The oxide stoichiometry was less than Cu2O at the maximum of the δΔ-curve, indicating that the CuO0.67-phase nucleated in the sample before the formation of Cu2O had been completed. During surface oxidation, the sensitivity of δΔ to the amount of oxygen was similar to that of copper single crystals. The sensitivity of δΔ to oxygen increased significantly while samples were oxidised to Cu2O and further: it was almost three times larger than the sensitivity of δΔ to oxygen for surface oxidation.