Growth and electronic properties of Rh and Au nanoclusters supported on copper oxides grown on Cu(110)

Yi-Lin Li^1*, Guan-Chen Liu¹, Yu-Ling Lai², Li-Chung Yu², Hung-Wei Shiu², Yao-Jane Hsu², Meng-Fan Luo¹

¹Department of Physics, National Central University, Taoyuan, Taiwan
²National Synchrotron Radiation Research center, Hsinchu, Taiwan

* Presenter:Yi-Lin Li, email:minicountryman2526@gmail.com

With reflection high energy electron diffraction (RHEED), scanning tunneling microscopy (STM) and synchrotron-based photoelectron spectroscopy (PES), we have studied Rh and Au nanoclusters supported on copper (Cu) oxide thin films grown on Cu(110) surface. Both Rh and Au clusters were grown by vapor deposition onto the Cu oxides at 300 K under ultrahigh vacuum conditions. The STM images showed that three-dimensional (3D) Rh clusters formed even at a sub-monolayer (ML) level; both the diameter and height of the Rh clusters increased with the coverage. The RHEED measurements indicated that the Rh clusters had an fcc phase and (110) facets parallel to the oxide surface. In contrast, Au clusters grew in a 2D fashion; no clear 3D Au clusters and no ordered structures were indicated at the investigated coverages. The PES results showed that the electronic properties of both Rh and Au clusters varied with their coverages. The PES spectra of Rh 3d core-levels for the Rh clusters at a small coverage (0.05-0.10 ML) exhibited a binding energy (BE) 0.7 eV smaller than the bulk value (Rh 3d_5/2 307.0 eV), and they shifted to a greater BE with increased coverage, despite of thickness of the Cu oxides. Those of Au 4f core-levels underwent a different evolution; their BE were generally 0.1 – 0.2 eV greater than the bulk value (Au 4f_7/2 84.0 eV) and varied little with the coverage. The electronic properties of Rh and Au nanoclusters supported on the Cu oxides of three different thickness showed similar behaviors, whereas their behaviors differs from those on Al₂O₃/NiAl(100), for which their core-level BE shifted negatively toward their bulk values with increasing coverages.

Keywords: Rh, Au, Nanoclusters, Copper oxide, Cu(110)