SYNTHESIS AND CHARACTERIZATION OF COPPER NANOWIRES USING SWIFT HEAVY ION

1. SYNTHESIS AND CHARACTERIZATION OF COPPER NANOWIRES USING SWIFT HEAVY ION Dr. David Forsyth British Institute of Technology & E-commerce (BITE)

2. structure of talk: • 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

3. 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

4. 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 semi-crystalline 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.

5. 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

6. 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

7. 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

8. Fabrication characteristics Characterization curve

9. copper deposition using NTF SEM picture of copper having diameter of 70 nm grown on the copper substrate.

10. 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

11. 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

12. 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 ion-track membrane. Morphology of electrodeposited copper nanowires was studied using scanning electron microscopy (SEM). Special uses of such nanowires has been discussed. END