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Growth of Carbon Nanotubes Using Cobalt Nanoparticles as Catalysts

Growth of Carbon Nanotubes Using Cobalt Nanoparticles as Catalysts. Nick McDonnell and Jay Pasquesi ECE 345 April 30, 2003. Overview. Objective Background Information Original Design Successes and Challenges Testing Conclusions. Project Objective. Objective :

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Growth of Carbon Nanotubes Using Cobalt Nanoparticles as Catalysts

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  1. Growth of Carbon Nanotubes Using Cobalt Nanoparticles as Catalysts Nick McDonnell and Jay Pasquesi ECE 345 April 30, 2003

  2. Overview • Objective • Background Information • Original Design • Successes and Challenges • Testing • Conclusions

  3. Project Objective • Objective: • To control the size and length of carbon nanotubes using CLCB-deposited cobalt nanoparticles as catalysts • Requirements • Interparticle distance <5m • Nanoparticle diameter <10nm

  4. What are Carbon Nanotubes? • Discovered by S. Ijima in 1991 • Tubular hexagonal arrays of graphene sheets • Can be single-walled or multi-walled (~2 nm SWCNT diameter) • Have metallic or semiconducting properties • Nanoelectronic Applications (i.e. FETs)

  5. CNT Background Info Chiral vector: • Ch= aV1 + bV2 Metallic: • a=b Semi-conducting: • (a-b)=3N Types: • Zigzag : (a,0) angle = 0° • Armchair: (a,a) angle = 30° • Chiral: (a,b) 0°>angle>30°

  6. Benefits of CNTs • Conduct electricity better than copper • Transmit heat better than diamond • 5 times stronger than steel • Max. tensile strength about 30GPa

  7. Design Overview • Precursor Development • Charged Liquid Cluster Beam (CLCB) Deposition • Catalytic Chemical Vapor Deposition (CCVD) • CNT Analysis

  8. Precursor Development • 2 Precursors: • Ni(TMP)4 • 0.003M • Co(EtAc)2 • 0.0025M, 0.003M, 0.005M, 0.009M

  9. CLCB Theory

  10. CLCB Setup

  11. CLCB Variables • Voltage Applied • Flow Rate • Deposition Time • Width of Tungsten Needle • E=V/r • Heater-to-Substrate Distance • E=V/d • Heater Temperature

  12. CCVD Theory • Introduce Methane Gas into furnace at 900°C • Temperature causes C-H bonds to break • Carbon attached to Cobalt’s dangling bonds • Strings of Carbon bonds form CNTs

  13. CCVD Variables • Furnace Temperature • Methane Gas Flow Rate • CCVD Duration

  14. Scanning Electron Microscopy (SEM) • Column generates electron beam that is aimed at sample and focused with EM fields • Images are obtained by detecting and processing electron scattering • Resolution of 5-10 nm • Fast Scanning Speed

  15. CNT Growth with Impurities Using Ni(TMP)4 Precursor

  16. CNT Growth From A Small Diameter Particle

  17. Short CNT Growth Between Cobalt Nanoparticles

  18. Long CNT Growth Between Cobalt Nanoparticles

  19. Single-Walled and Multi-Walled CNT Growth Between Particles Single-Walled Multi-Walled

  20. Atomic Force Microscopy (AFM) • Two modes: Contact & Tapping* • Tip diameter used was 5-10 nm • Diameter will affect spreading effects • Atomic Resolution • Small Damage Effects • Slow Scanning Speed

  21. AFM • 1. Laser • 2. Mirror • 3. Photodetector • 4. Amplifier • 5. Register • 6. Sample • 7. Probe • 8. Cantilever

  22. CNT Growth Between Two Nanoparticles

  23. AFM Analysis ofCNT Diameter

  24. Problems and Solutions • Glass Capillary very fragile • Switched to Polymer Nozzle • Durable • Diameter constant • Air Bubbles formed easily with new nozzle • Switched back to Glass Capillary

  25. Conclusions from SEM, AFM • For growth of CNTs, need small diameter nanoparticles (<10nm) • Large interparticle distance = long CNTs • Small interparticle distance = short CNTs

  26. Effects of CLCB on CNT Growth • Smaller particle diameter with: • Increasing Voltage • Decreasing Flow Rate • Decreasing Precursor Concentration • Smaller interparticle distance with: • Increasing Deposition Time • Increasing Precursor Concentration • Optimize CLCB Variables

  27. CNT Length vs.Interparticle Distance

  28. CNT Diameter vs.Small Particle Diameter

  29. Final Conclusions • Possible to control size and diameter of CNTs by varying CLCB parameters • Difficult to grow CNTs in a specific area • Can possibly use masking

  30. Acknowledgements • Prof. Kevin Kim for guidance and use of his facilities • Prof. Choi for patented precursors and expertise • Tim Day and the rest of Prof. Kim’s staff for their assistance and knowledge • Matt Olson for his advice

  31. Questions?

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