Temperature-dependent structuring of Au-Pt bimetallic nanoclusters on a thin film of Al2O3/NiAl(100).
Au-Pt bimetallic nanoclusters on a thin film of Al(2)O(3)/NiAl(100) undergo significant structural evolution on variation of the temperature. Au and Pt deposited sequentially from the vapor onto thin-film Al(2)O(3)/NiAl(100) at 300 K form preferentially bimetallic nanoclusters (diameter ≦ 6.0 nm and height ≦ 0.8 nm) with both Au and Pt coexisting at the cluster surface, despite the order of metal deposition. These bimetallic clusters are structurally ordered, have a fcc phase and grow with their facets either (111) or (001) parallel to the θ-Al(2)O(3)(100) surface. Upon annealing the clusters to 400-500 K, the Au atoms inside the clusters migrate toward the surface, resulting in formation of a structure with a Pt core and an Au shell. Annealing the sample to 500-650 K reorients the bimetallic clusters--all clusters have their (001) facets parallel to the oxide surface--and induces oxidation of Pt. Such annealed bimetallic clusters become encapsulated with the aluminium-oxide materials and a few Au remain on the surface.
Department of Physics and Center for Nano Science and Technology, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan. mfl28@phy.ncu.edu.tw
Meng-Fan
MF
Luo
Chao-Chuan
CC
Wang
Chen-Sheng
CS
Chao
Chiun-Yu
CY
Ho
Cheng-Ting
CT
Wang
Won-Ru
WR
Lin
Yin-Chang
YC
Lin
Yu-Lin
YL
Lai
Yao-Jane
YJ
Hsu