Reflection high energy electron diffraction characterization of Co clusters electrodeposited on Au(100) electrode

CIC nanoGUNE Seminars

Speaker

Mauscheng Zei, Department of Physics, National Central University, Taiwan, Taiwan

When

2010/07/20
13:00

Place

nanoGUNE seminar room, Tolosa Hiribidea 76, Donostia - San Sebastian

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Cobalt was electrodeposited onto the reconstructed Au(100) electrode in 0.25 M Na2SO4 \+ 0.1 mM CoSO4, yielding nanometer sized Co clusters of ca. 3 nm in diameter. The as-prepared Au(100) electrode was transferred via an argon environment and subsequently examined by reflection high energy electron diffraction (RHEED) to characterize the epitaxial growth of Co nano-clusters on Au(100). It is found that Co clusters prefer to pack in the face-centered cube (fcc) rather the hexagonal-closed pack (hcp) phase on Au(100), and grow with their (-110) plane parallel to the Au(100) substrate and their [110] axis aligned parallel to the [011] direction of the Au(100) substrate. The preferential growth of the fcc Co phase is apparently driven by the lower lattice strain between the (-110) plane of Co clusters and the Au(100) substrate network. (2) Investigations of the initial stages of the twinned Pt nano-clusters formation and their epitaxial growth on Ru(0001) as well as the epitaxial growth of Ru nano-particles on Pt(111) M.S. Zei Department of Physics, National Central University, No. 300 Jungda Rd., Jungli 32054, Taiwan, zei@phy.ncu.edu.tw ** ** **Abstract** The epitaxial growth of Pt and Ru deposits by spontaneous, as well as by dynamic, electrodeposition onto Ru(0001) and Pt(111), respectively, have been studied by reflection high energy electron diffraction (RHEED) and Auger electron spectroscopy (AES). For the Pt deposit on Ru(0001), at submonolayer range, it preferably grows compressed commensurate bilayer thick islands on Ru(0001). This is the first time that RHEED observation of the onset of Pt twinning occurs in ca. 2-3 layer thick islands on Ru at room temperature, at which the surface strain due to the 2.5% lattice mismatch of Pt and Ru remains intact. For multilayer thick islands (> 6 ML) ordered reflection twins (diameter of ~ 3 nm) develop and are embedded in a (111) matrix with an incoherent (11-2) twin plane normal to Ru(0001) and aligned with their [-110] direction parallel to the [11-20] Ru(0001) substrate direction. For the Ru deposit on Pt(111), at ~0.2 ML a strained (1x1) monoatomic layer is formed due to the 2.5 % lattice mismatch of Ru and Pt. Increasing the coverage up to ~0.64, the second Ru layer is found to relieve the strain in the first layer, giving rise to dislocations and Ru relaxes to its bulk lattice constant. Multilayers of Ru (> 1ML) result in (0001) nanocluster formation aligned with its [11-20] direction parallel to the [-110] Pt(111) substrate direction. The Pt and Ru clusters grow epitaxially with facets of a hexagonal unit cell on Ru(0001) and Pt(111), respectively, to decrease the interface strain.