Electron microscopy and spectroscopy investigations of CuOx-CeO2−δ/Si thin films

CuOx-CeO2−δ/Si thin films were elaborated by pulsed laser deposition. At the surface of all CuOx-CeO2−δ thin films, Ce4+ and Cu+1 ions were present. Depth profiles indicated that a Cu2O rich layer, roughly 40 nm thick, covered the CuOx-CeO2−δ thin films. Apart from the copper enriched surface, the copper repartition in the thin films is highly inhomogeneous and two types of copper oxides, CuO and Cu2O, in form of rounded grains 20 nm were identified in the thin films. At least 10 at.% Cu seems to be inserted in the ceria lattice. Pure CeO2 grains result from the deposition of tetrahedron-like nanoclusters followed by coalescence of (1 1 1) faces, and CuOx-CeO2−δ grains from the deposition of cube-like nanoclusters followed by coalescence of (1 1 0) faces. The good catalytic performances of the CuOx-CeO2−δ/Si thin films are due to active {1 0 0} ceria exposed facets covered by Cu2O nanoparticles.