Transcript Research Methods and Methodologies

SYNTHESIS AND
CHARACTERIZATION OF
COPPER NANOWIRES
USING SWIFT HEAVY ION
Dr. David Forsyth
British Institute of Technology & E-commerce (BITE)
structure of talk:
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why copper (Cu) nanowires ?
experimental procedure
irradiation set up at GPSC
copper deposition on copper substrate
block diagram of copper nanowires
fabrication characteristics
SEM picture
future uses
copper (Cu) nanowires:
• “good old-fashioned copper” is good for nanowires – cheap and easy
to produce, superb mechanical properties and electro-thermal
conductivities, more amenable for nanocomposite mixing etc.
• they may complement or replace carbon nanotubes in some
applications and are the most feasable nanostructure for interconnects
in future nanodevices (not communication systems)
• but less anti-corrosive (therefore should be capped)
•
in this work are electrochemically synthesised using etched pores in
polycarbonate ion-track membrane
experimental
• Makrofol KG (polycarbonate from Bayer AG of UK), 20 μm thick were
prepared by irradiating the foils with heavy ion 28Si, 100 MeV with ion
fluence of 1x105 ions/cm2, 2.5x 105 ions/cm2, 5x105 ions/cm2, 1x106
ions/cm2 and 2x106 ions/cm2 at the 15 MV Pelletron accelerator of the
Inter University Accelerator Centre (IUAC), New Delhi, India
• the stopping range of Si ion beam of this energy in the given material using
SRIM code id found to be 32.25 μm, hence the ion beam will simply pass
through a polymer of the given thickness. But in order to have through
etched pores, we have to etch our samples.
• Makrofol KG used since it has density of 1.2 g/cm3, melting point 220 c,
is a perfect insulator, is highly sensitive for the formation of tracks, is semicrystalline in nature and, due to extremely high track etch ratio, it is able to
produce extremely fine cylindrical or conical pores very easily, as it can be
easily dissolved in several organic solutions.
irradiation set up at GPSC:
•chamber is 0.6 m in height and
1.5 in diameter
•vacuum inside is around 1x10-6
mbar
•GPSC is situated at the angle of
20º to the beam line
•beam falls normally on the gold
target of thickness 1mg/cm2 and
scattered at angle of 20º and
falls
normally
to
ladder
containing samples
•both surface barrier detector
(SBD) and Faraday Cup (FC)
detect number of counts/sec, and
connected to pre-amplifier and
scanning channel analyzer
Irradiation set up at GPSC
Actual Fluence = (Detector counts per
sec/Faraday cup counts per sec) x Fluence
copper deposition on copper substrate
• samples were etched in 6N
NaOH, at 60°C for 30 min in a
temperature controlled water bath
(found to be the optimum
conditions to produce etched
through pores for
electrodeposition)
• 80 mm long cylindrical
structure perpex cathode
and anode are made of
copper and are
detachable
• the NTF covers the
cathode and is sealed
thoroughly by an O-ring
Design of etching cell
Block diagram of copper nanowires
• after the electrodeposition
was over, the electrolyte
was drained out and
cathode flushed with 3%
dilute H2SO4 and air-dried
• the NTF was carefully
removed, washed with
distilled water, ethanol and
air dried. On the respective
sides of the NTF, metallic
structure of copper could be
seen
Block diagram of copper nanowires
Fabrication characteristics
Characterization curve
copper deposition using NTF
SEM picture of copper having diameter of 70 nm grown on the copper
substrate.
future uses:
• copper nanowires could serve as interconnects in
electronic device fabrication and as electron emitters in
a television-like, very thin flat-panel display known as
a field-emission display
Block diagram
of field emission
studies
nanowires (similar to the ones fabricated in this work) have many
other potential applications:
• in bio-sensing, molecular electronics, hydrogen storage, memory and display
devices and other sensors
• for example, nanowires can be used to create a memory device - a research
group at Hewlett-Packard (HP) in conjunction with the University of California
(UCLA) have demonstrated a memory cell which can be formed by the
intersection of two nanowires. HP has advanced the idea further in this field
and has prepared a complicated array of nanowires for creating a transistor-like
device by growing nanowires from different semiconductors.
• also, workers at the University of Southern California and NASA Research
Centre are predicting a 40 gigabite per square centimeter storage capacity for an
indium oxide-based nanowire memory device they have created
• nanowires are also expected to have tremendous potential in the field of
electronics and for the most important elements of molecular electronics
• they are also used in switches and light-emitting diodes
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nanowire-based sensors can also detect diseases in blood samples. For this
purpose, a nanowire is first functionalized by attaching nucleic acid molecules to
it. If a fibrosis gene is present in blood sample, the conductance of nanowire
changes. Thus nano wires have huge potential for use as biosensors
DISCUSSION
Copper nanowires have been electrochemically
synthesized using etched pores in polycarbonate iontrack membrane. Morphology of electrodeposited
copper nanowires was studied using scanning
electron microscopy (SEM). Special uses of such
nanowires has been discussed.
END