| dc.description.abstract | By utilizing the reflection high energy diffraction (RHEED), scanning tunneling microscopy (STM), and X-ray photoelectron spectroscopy (XPS), we have investigated the growth and electronic properties of Rh and Au nanoclusters grown on CuO/Cu(110).
Rh atoms that are deposited on CuO/Cu(110) at 300 K self-assemble into nanoclusters in a 3D (three-dimensional) fashion even at small coverage (0.09 ML), indicated by STM. RHEED patterns also reflect the 3D structure of Rh nanoclusters, and are consistent with STM results. The averaged diameter of these nanoclusters increases with Rh coverage, and saturates at around 1.50 nm when above 0.62 ML. However, the averaged height does not increase with coverage but maintains at around 0.22 nm. The cluster density also saturates when above 0.62 ML, together with the unchanged size of Rh nanoclusters, the clusters at the lower position may merge into a Rh film. Electronic structure of Rh nanoclusters evolves with coverage. At small coverages (0.02 to 0.12 ML), Rh 〖3d〗_(5/2) centers at 306.3 eV which is 0.7 eV smaller than the bulk value (307.0 eV). On increasing the Rh coverage, Rh 〖3d〗_(5/2) shifts toward it bulk value, and finally locates at 306.8 eV when at 1.44 ML. This unusual shift of Rh 3d doublet may indicate a charge transfer from substrate or support to Rh nanoclusters.
The Au nanoclusters grow in a 2D fashion at sub-monolayer level, indicated by STM. Au films form on the surface when increasing the coverage, identified by the STM images and RHEED patterns. The electronic structure of Au nanoclusters also evolves with coverage. At the low coverages (≤ 0.23 ML), Au 〖4f〗_(7/2) centers at 84.1 eV which is 0.1 eV higher than its bulk value (84.0 eV), and increases to 84.2 eV at higher coverage. The abnormal shift of the Au 4f doublet may indicate that the chemical enviroment on the Au surface is modified by an extra element, such as the oxygen atoms floating to the CuO surface. | en_US |