EXPERIMENTAL

RESULTS AND DICUSSIONS (CONTrsquoD)

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 1 A Huczko App Phy A 70 (2000) 365-376

2 R Inguanta S Piazza C Sunseri Electrochem Commun 11 (2009) 1385-1388

3 S L Xu X Sun H Ye T You X Y Song S X Sun Mater Chem and Phy 120 (2010) 1-5

4 G Kartopu O Yalcin Electrodeposited Nanowires and Their Applications ISBN 978-953-

7619-88-6 pp228 2000

5 ZH Yang ZW Li L Liu LB Kong J Magn Magn Mater 323 (2011) 2674-2677

6 Q L Xu G W Meng X B Wu Q Wei M G Kong X G Zhu Z Q Chu Chem

Mater 21 (2009) 2397-2402

7 Chowdhury D P Casey J F Rohan Electrochem Commun 11 (2009) 1203-1206

8 W Lee R Ji U Gosele and K Nielsch Nat Mater 5 (2006) 741-747

9 A Santos L Vojkuvka J Pallares J Ferre-Borrull L F Marsal J Electroanal Chem

632 (2009) 139-142

10 S S Djokic J Electrochem Soc 143 (1996) 1300

11 AJ Bard R Parsons J Jordan J Standard Potentials in Aqueous Solution Marcel

Dekker New York 1985

CONCLUSION bull Regular and uniform arrays of Cu nanowires were successfully synthesized by a simple metal

displacement deposition method

bull 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

bull 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 bull 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

bull Study potential factors affecting the redox deposition to investigate optimal conditions for this

fabrication method

XRD Results

Properties of Cu nanowires

bull Face-centered cubic

crystal structures

bull Strong texturing

bull 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 peaks 3 intense peaks

Stage 1

Foil DC anodized in

05M H2C2O4(aq) at

40V for 10-15min

9999

pure Al foil Annealed at 500degC 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

05ml of 1M

NaOH(aq)

bull Morphology of AAO template

and Cu nanowire arrays examined

by Field Emission SEM

bull Crystalline structures of

nanowires identified by XRD

Pre

par

atio

n o

f A

AO

Te

mp

late

s D

ep

osi

tio

n o

f C

u

Nan

ow

ire

Arr

ays

Ch

arac

teri

sati

on

Orderly upstanding Cu nanowires with bases inside AAO templates

0141 μm

0136 μm

0136 μm

0151 μm

(2a) Top-view (2b) Side-view

Islands consisting of bundles of Cu nanowires

(2d) Low magnification

1359 nm

1070 nm

1163 nm

(2e) High magnification

Alumina matrix of AAO template has almost been dissolved away

Cu Nanowires Characterisation

(1a) Top-view (1b) Cross-sectional view

6988 microm 7183 microm

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

bull Pore center distance 160 nm

bull Pore diameter 120 nm

bull Thickness of AAO template 70 μm

bull 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

01M CuCl2(aq)

for 4h

Cut into

Stage 2

Voltage

increased to

60V at 06Vs-1

and

maintained

for 2h

Image taken from httpmediadigikeycomphotos3M20Photos1170-775EX105Ejpg

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 ZH Yang ZW Li L Liu LB Kong J Magn Magn Mater 323 (2011) 2674-2677