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Open Access Nano Express

Epitaxial deposition of silver ultra-fine nano-clusters on defect-free surfaces of HOPG-derived few-layer graphene in a UHV multi-chamber by in situ STM, ex situ XPS, and ab initio calculations

Gebhu F Ndlovu12, Wiets D Roos2, Zhiming M Wang3, Joseph KO Asante4, Matete G Mashapa1, Charl J Jafta2, Bonex W Mwakikunga15* and Kenneth T Hillie12*

Author Affiliations

1 National Centre for Nano-structured Materials, Council for Scientific and Industrial Research (CSIR), Meiring Naude Road, Brummeria, 395 Pretoria, 0001, South Africa

2 Department of Physics, University of the Free State, 205 Nelson Mandela Drive, 339 Bloemfontein, 9300, South Africa

3 State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China

4 Department of Physics, Tshwane University of Technology, Private Bag X680 Pretoria, 0001, South Africa

5 Department of Physics, University of Malawi-The Polytechnic, Private Bag 303, Chichiri, Blantyre, 0003, Malawi

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Nanoscale Research Letters 2012, 7:173  doi:10.1186/1556-276X-7-173

Published: 6 March 2012

Abstract

The growth of three-dimensional ultra-fine spherical nano-particles of silver on few layers of graphene derived from highly oriented pyrolytic graphite in ultra-high vacuum were characterized using in situ scanning tunneling microscopy (STM) in conjunction with X-ray photoelectron spectroscopy. The energetics of the Ag clusters was determined by DFT simulations. The Ag clusters appeared spherical with size distribution averaging approximately 2 nm in diameter. STM revealed the preferred site for the position of the Ag atom in the C-benzene ring of graphene. Of the three sites, the C-C bridge, the C-hexagon hollow, and the direct top of the C atom, Ag prefers to stay on top of the C atom, contrary to expectation of the hexagon-close packing. Ab initio calculations confirm the lowest potential energy between Ag and the graphene structure to be at the exact site determined from STM imaging.