Epitaxial growth of cobalt clusters on the bare and the oxide film grown on NiAl(1 0 0) surfaces |
| |
Authors: | MS Zei |
| |
Institution: | Department of Physics, National Central University, No. 300 Jungda Road, Jungli 32054, Taiwan |
| |
Abstract: | The structure of the nano-sized cobalt clusters on bare NiAl(1 0 0) and an oxidized NiAl(1 0 0) surfaces have been investigated by AES, LEED and RHEED. The deposition of Co onto bare NiAl(1 0 0) at room temperature led to small crystalline Co grains and surface asperities of substrate. The latter is likely induced by replacement of surface Al, Ni atoms by Co deposit. At 800 K Co particles aggregate to form clusters, but incorporation of Co into bulk NiAl(1 0 0) could occur upon annealing at 900 K. On the other hand, pure face-centered cubic (fcc) phase of Co crystallites of ≈1 nm in diameter with inclusion of smaller-sized particles (D < 1 nm) are observed on Θ-Al2O3 after Co deposition at room temperature. After annealing the Co nano-clusters grow larger at expense of small particles (D ≈ 3 nm), where the 1 1 0] and −1 1 0] axis of the Co(0 0 1) facets are parallel to the 1 0 0] and 0 1 0] directions of (0 0 1)oxide, respectively. The in-plane lattice constant of Co clusters is ca. 4% larger than that of bulk Co, yielding less strain at the Co/oxide interface. A 15° ± 10% random orientation of the normal to (0 0 1) facet of Co clusters with respect to (0 0 1)oxide surface was deduced from the “arc”-shape reflection spots in RHEED. These results suggest that both orientation and phase of Co clusters are strongly affected by the nature and structure of oxide surface. |
| |
Keywords: | Reflection high-energy electron diffraction (RHEED) Auger electron spectroscopy Cobalt Aluminum oxide Clusters |
本文献已被 ScienceDirect 等数据库收录! |
|