Abstract
Metal nanoparticles embedded into a semiconductive matrix represent a promising material for widely sought advanced technological applications. We focused our interest on the preparation of TiO2 matrix with embedded Cu nanoparticles.
In particular, we studied the effect of reactive discharge (Ar/O-2) exposition on copper oxidation, which can result in two stable forms: cuprous oxide (Cu2O) and cupric oxide (CuO). Copper nanoparticles, of size in range 10-50 nm, were produced by magnetron sputtering in combination with gas aggregation.
The beam of Cu nanoparticles was impinging onto a silicon substrate which was directly exposed to a reactive Ar/O-2 magnetron discharge providing sputtering of Ti target at the same time. The properties of deposited nanocomposite Cu(O-x)-TiO2 were investigated by X-ray photoelectron spectroscopy, grazing incidence X-ray diffractometry, X-ray reflectometry and scanning electron microscopy techniques to reveal the nanocomposite properties and to understand the oxidation process of embedded Cu nanoparticles.
It was found that CuO is preferentially formed if copper is exposed to active oxygen species (O+, O-, O*. etc.) produced in the reactive magnetron discharge. On the other hand, Cu2O was observed in the case of copper reaction in ambient Ar/O-2 atmosphere.
As a result, two possible copper oxidation mechanisms are proposed, employing chemical kinetics.