1. EXPERIMENTAL
RESULTS AND DICUSSIONS (CONT’D)
3 intense peaks (200) peak was
larger than
expected for a
random
polycrystalline
sample
Cu NANOWIRE ARRAYS PREPARED BY A
SIMPLE REDOX DEPOSITION METHOD
Leong Feng Ping Angela
INTRODUCTION
Metallic nanowires possess high functionality due to their multiple attractive properties and
characteristics, with potential applications in various fields like nanoscale electronics and
magnetic devices. Cu is particularly desirable due to its electrical properties and low cost. Yet the
fabrication of Cu nanowires remains largely limited; popular template-based methods of
electrodeposition and electroless deposition are energy-consuming, environmentally
unfriendly, non-facile and difficult to control.
PURPOSE
To report the synthesis of Cu nanowires in anodic aluminum oxide (AAO) templates using a
simple metal displacement deposition method, which combines the template deposition and
metal displacement reaction. This method is based on galvanic contact between the sputtered
noble metal film, covering the bottom of the template, and a less noble metal, partially exposed
to the solution.
REFERENCES
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4. G. Kartopu, O. Yalcin, Electrodeposited Nanowires and Their Applications, ISBN 978-953-
7619-88-6, pp.228, 2000.
5. Z.H. Yang, Z.W. Li, L. Liu, L.B. Kong, J. Magn. Magn. Mater. 323 (2011) 2674-2677.
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Mater. 21 (2009) 2397-2402.
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632 (2009) 139-142.
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11. A.J. Bard, R. Parsons, J. Jordan, J. Standard Potentials in Aqueous Solution, Marcel
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CONCLUSION
• Regular and uniform arrays of Cu nanowires were successfully synthesized by a simple metal
displacement deposition method.
• This fabrication technique is easy to control and low-cost, as the deposition can be carried out
at room temperature without requiring energy, organic surfactants, specific equipment, or
modification on the pore walls.
• Considering copper is one of the most important metals in modern electronic technology, this
process can be useful for industrial manufacture of copper nanowires.
RESULTS AND DISCUSSIONS
AAO Template Characterisation
FUTURE WORK
• Extension of method to fabrication of nanowires of other metals and heterogeneous alloys,
since the Al3+/Al redox pair has a lower standard reduction potential than many metallic ions
• Study potential factors affecting the redox deposition to investigate optimal conditions for this
fabrication method
XRD Results
Properties of Cu nanowires:
• Face-centered cubic
crystal structures
• Strong texturing
• Preferred growth direction in the (200)
crystal plane
(200) peak
was larger
than expected
for a random
polycrystalline
sample
3 intense peaks
SEM images of Cu nanowire arrays after template removal
Redox Deposition Scheme
3 intense peaks3 intense peaks
Stage 1:
Foil DC anodized in
0.5M H2C2O4(aq) at
40V for 10-15min
99.99%
pure Al foil
Annealed at 500°C in
air for 5h and
cleaned with acetone
Immersed in 6 wt%
H3PO4(aq) for ~40min
to widen pores
Al-surrounded AAO
floated on 6 wt% H3PO4(aq)
to dissolve barrier layer
100nm Pt layer
sputtered on one side
of template to form
conductive layer
Sample
sputtered
with Pt thin
layer in
vacuum
Alumina film on
surface partially
dissolved by
0.5ml of 1M
NaOH(aq)
• Morphology of AAO template
and Cu nanowire arrays examined
by Field Emission SEM
• Crystalline structures of
nanowires identified by XRD
PreparationofAAOTemplatesDepositionofCu
NanowireArrays
Characterisation
Orderly upstanding Cu nanowires
with bases inside AAO templates
0.141 μm
0.136 μm
0.136 μm
0.151 μm
(2a) Top-view (2b) Side-view
Islands consisting of bundles of Cu nanowires
(2d) Low magnification
135.9 nm
107.0 nm
116.3 nm
(2e) High magnification
Alumina matrix of AAO template has almost been dissolved away
Cu Nanowires Characterisation
(1a) Top-view (1b) Cross-sectional view
69.88 µm
71.83 µm
SEM images of blank AAO templates after pore widening SEM image of cross-section of
AAO template after infiltration,
with Cu nanowires embedded
in pores
• Pore center distance: ̴160 nm
• Pore diameter: ̴120 nm
• Thickness of AAO template: ̴70 μm
• Pores are distributed in perfect hexagonal
order in defect-free area.
ACKNOWLEDGEMENTS
This work was supported by the Young Defence Scientists Programme (YDSP), Ministry of Defence, Singapore. I would like to thank Mr. Yang Zhihong from Temasek Laboratories, NUS, for guiding me through the
experiments, instructing me in the background knowledge, and clarifying my doubts, as well as Mr. Murali Krishnaswamy for his guidance during the editing of the report, and aiding with administrative details.
At cathode:
Cu2+ + 2e-  Cu
At anode:
Al  Al3+ + 3e-
Cl- ions in solution etch away the
alumina layer on Al foil, exposing pure Al
Cu2+
Cu2+
(1c)
Average diameter of
nanowires is ̴120 nm
(2c)
Remaining
Al on back
of template
etched with
1M CuCl2(aq)
100nm Pt layer sputtered on
one side of template to
form conductive layer
Template
infiltrated by
0.1M CuCl2(aq)
for 4h
Cut into
Stage 2:
Voltage
increased to
60V at ̴0.6Vs-1
and
maintained
for ̴2h
Image taken from:
http://media.digikey.com/photos/3M%
20Photos/1170-7.7%5EX10%5E.jpg
*All images and graphs are self-taken and self-drawn unless otherwise stated.
Image taken from: Microstructure and magnetic properties of Co-Cu nanowire arrays fabricated by galvanic
displacement deposition. Z.H. Yang, Z.W. Li, L. Liu, L.B. Kong, J. Magn. Magn. Mater. 323 (2011) 2674-2677.