Master Presentation Part 2

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Localized growth of Multi-Walled Carbon Nanotubes

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  • Factors contributing to variations
  • Master Presentation Part 2

    1. 1. Electrical Properties Factors <ul><li>Contact: </li></ul><ul><ul><li>Number of concentric layers in contact with electrode [19] </li></ul></ul><ul><ul><li>Contact geometry (side vs tip) [20] </li></ul></ul><ul><ul><li>Contact area [23] </li></ul></ul><ul><ul><li>Electrode materials used [21, 22] </li></ul></ul><ul><ul><li>Interface coupling (scattering induced by defects; tunneling) [24, 25] </li></ul></ul><ul><li>CNT: </li></ul><ul><ul><li>Consistency across different samples </li></ul></ul><ul><ul><li>Semiconducting vs metallic [19] </li></ul></ul><ul><ul><li>Outer-layer vs inner-layer [26, 27] </li></ul></ul><ul><ul><li>Defect density [28] </li></ul></ul><ul><li>Literature: 34 Ω to ~10 MΩ </li></ul>
    2. 2. I-V characteristics <ul><li>9 CNTs connections </li></ul><ul><li>Ohmic response </li></ul><ul><li>~ 480 kΩ </li></ul><ul><li>Stable, repeatable response </li></ul>
    3. 3. I-V characteristics <ul><li>Unstable at same pressure </li></ul><ul><li>~100x reduction in conductivity after SEM </li></ul>
    4. 4. I-V characteristics <ul><li>~ 7 kΩ ( > 10 CNT connections) </li></ul><ul><li>No electrical connection after some CNT breakage </li></ul>
    5. 5. I-V characteristics
    6. 6. Si-CNT contact <ul><li>Assumptions: </li></ul><ul><ul><li>Outercell contributes most current </li></ul></ul><ul><ul><li>d > 16nm => bandgap smaller than 0.026eV </li></ul></ul><ul><ul><li>Metallic </li></ul></ul>
    7. 7. Si-CNT contact <ul><li>W ~ 9 nm </li></ul><ul><li>Tunneling dominate </li></ul><ul><li>Specific contact resistance ~10 -4 Ωcm 2 </li></ul><ul><li>Contact area ~ 2.5x10 -11 cm 2 </li></ul><ul><li>Contact resistance (~0.5-5 MΩ) vs overall resistance of ~ 2.5 MΩ </li></ul>
    8. 8. Native oxide <ul><li>~10Å thickness </li></ul><ul><li>Breakdown field ~3x10 7 V/cm </li></ul><ul><li>Voltage applied (V2~5V, V1~7V) </li></ul>
    9. 9. Non-ohmic I-V characteristics <ul><li>Non-ohmic </li></ul><ul><li>Lacks apparent “turn-on” voltage </li></ul><ul><li>Somewhat symmetrical about origin </li></ul>
    10. 10. Non-ohmic I-V characteristics <ul><li>~8x10 -7 A at 1V (tunneling through 10Å oxide) </li></ul><ul><li>Tunneling current exponential with applied voltage </li></ul>a) [30], b) [31]
    11. 11. Non-ohmic characteristics <ul><li>At low bias (<0.25 V) </li></ul><ul><ul><li>Limited by tunneling current density ~10 A/cm 2 , exponentially increasing) </li></ul></ul><ul><li>At high bias (>0.3 V) </li></ul><ul><ul><li>Limited by combination of CNT and contacts resistance, ohmic) </li></ul></ul><ul><li>Symmetrical about origin </li></ul>
    12. 12. Native oxide <ul><li>Breakdown voltage ~3x10 7 V/cm </li></ul><ul><li>Oxide thickness < 20Å </li></ul><ul><li>Gradient past breakdown => ~270 kΩ </li></ul>
    13. 13. Si-CNT-Au system
    14. 14. Si-CNT-Au system <ul><li>Overall resistance ~170 kΩ, ~6.7 MΩ </li></ul>
    15. 15. Pressure-sensing <ul><li>Pressure-sensing observed in ohmic device </li></ul>
    16. 16. Pressure-sensing <ul><li>Negative resistance coefficient of temperature </li></ul>
    17. 17. Contact annealing <ul><li>Electrically heat up secondary heater </li></ul><ul><li>Fragments of CNTs observed post-heating </li></ul>
    18. 18. Contact annealing <ul><li>Heating in furnace ~500 0 C </li></ul><ul><li>No apparent physical change, though conductivity decreases </li></ul>
    19. 19. CNT-based probe electrode <ul><li>Intracellular (~100mV) vs Extracellular (~100µV) </li></ul><ul><li>Patch cell (“gigaohm seal”) </li></ul>
    20. 20. CNT-based probe electrode
    21. 21. Fabrication steps <ul><li>Parylene-C </li></ul><ul><ul><li>high volume resistivity </li></ul></ul><ul><ul><li>Biocompatibility </li></ul></ul><ul><ul><li>conformal deposition </li></ul></ul><ul><ul><li>Melting temp (290 0 C) </li></ul></ul>
    22. 22. Fabrication steps
    23. 23. CNT-based probe electrode
    24. 24. Impedence attempts
    25. 25. Onion cell connection
    26. 26. Conclusions <ul><li>Fine-tune localized growth of CNTs </li></ul><ul><li>In-situ monitoring and controlled growth of CNTs </li></ul><ul><li>Investigate the electrical properties of Si/CNT/Si system </li></ul><ul><li>Pressure-sensing & cell electrode probe </li></ul>
    27. 27. Publications <ul><li>Takeshi Kawano, Dane Christensen, Supin Chen, Chung Yeung Cho , Liwei Lin, “Formation and characterization of silicon/carbon nanotube/silicon heterojunctions by local synthesis and assembly”, Applied Physics Letters , 89(1), (2006) </li></ul><ul><li>Takeshi Kawano, Chung Yeung Cho , Liwei Lin, “Carbon nanotube-based nanoprobe electrode”, IEEE International Conference of Nano/Micro Engineered and Molecular Systems Conference (2007) </li></ul><ul><li>Takeshi Kawano, Chung Yeung Cho , Liwei Lin, “In-situ controlled growth of carbon nanotubes by local synthesis”, IEEE International Conference on Micro Electro Mechanical Systems Conference (2007) </li></ul><ul><li>(Not related to this CNT work) Kyoungsub Shin, Weize Xiong, Chung Yeung Cho , C. Rinn Cleavelin, Thomas Schulz, Klaus Schruefer, Member, IEEE , Paul Patruno, Lee Smith, and Tsu-Jae King Liu, “Study of bending-induced strain effects on MugFET performance”, IEEE Electron Device Letters , 27 (8), 671-673 (2006) </li></ul>
    28. 28. Acknowledgement <ul><li>Prof Lin, Prof King </li></ul><ul><li>Takeshi Kawano </li></ul><ul><li>Brian, Sha Li, Lei Luo, Ethan, Takashi </li></ul><ul><li>Other lab mates </li></ul><ul><li>EML folks </li></ul><ul><li>Tammy, my family </li></ul>
    29. 29. References <ul><li>Eikos.com company info </li></ul><ul><li>Anyuan Cao et al., “ Super-compressive foamlike carbon nanotube films ”, Science, 310 , 1307-1310 (2005) </li></ul><ul><li>Nantero.com NRAM movie </li></ul><ul><li>Ray H. Baughman et al., “ Carbon nanotubes - the route toward applications ”, Science, 297, 787-782 (2002) </li></ul><ul><li>Nadine Wong Shi Kam et al., “ Carbon nanotubes as multifunctional biological transporters and near-infrared agents for selective cancer cell destruction ”, PNAS, 102 (33), 11600-11605 (2005) </li></ul><ul><li>T. D. Yuzvinsky et al., “ Engineering nanomotor components from multi-walled carbon nanotubes via reactive ion etching ”, AIP Conference Proceedings 723 , 512-515 (2004) </li></ul><ul><li>Mei Zhang et al., “ Strong, transparent, multifunctional, carbon nanotube sheets ”, Science 309 , 1215-1219 (2005) </li></ul><ul><li>Hongjie Dai, “Carbon nanotubes: opportunities and challenges”, Surface Science, 500, 218-241 (2002) </li></ul><ul><li>Dane Cristensen, “ Localized synthesis, assembly and application of carbon nanotubes ”, PhD dissertation in Mechanical Engineering in UC Berkeley (2005) </li></ul>
    30. 30. References <ul><li>Bonard, J.M. et al., “ Purification and size-selection of carbon nanotubes”, Advanced Materials, 9 (10), 827-831 (1997) </li></ul><ul><li>Scott, C.D. et al., “ Growth mechanisms for single-wall carbon nanotubes in a laser-ablation process”, Applied Physics a-Materials Science & Processing, 72 (5), 573-580 (2001) </li></ul><ul><li>Li, J. et al., “ Highly-ordered carbon nanotube arrays for electronics applications”, Applied Physics Letters, 75 (3), 367-369 (1999) </li></ul><ul><li>Hata, K. et al., “ Water-assisted highly efficient synthesis of impurity-free single-waited carbon nanotubes”, Science, 306 (5700), 1362-1364 (2004) </li></ul><ul><li>Huang, S.M., “ Growth mechanism of oriented long single walled carbon nanotubes using &quot;fast-heating&quot; chemical vapor deposition process”, Nano Letters, 4 (6), 1025-1028 (2004) </li></ul><ul><li>Bower, C., “ Plasma-induced alignment of carbon nanotubes”, Applied Physics Letters, 77 (6), 830-832 (2000) </li></ul><ul><li>Yuegang Zhang et al., “Electric-field-directed growth of aligned single-walled carbon nanotubes”, Applied Physics Letters, 79(19), 3155-3157 (2001) </li></ul><ul><li>J. Gavillet et al., “ Root-growth mechanism for single-walled carbon nanotubes ”, Physical Review Letters, 87(27), 275504 (2001) </li></ul>
    31. 31. References <ul><li>C. Ducati, “Temperature selective growth of carbon nanotubes by chemical vapor deposition”, Journal of Applied Physics, 92(6), 3299-3303 (2002) </li></ul><ul><li>P. J. de Pablo et al., “A simple, reliable technique for making electrical contact to multiwalled carbon nanotubes”, Applied Physics Letters, 74, 323–325 (1999) </li></ul><ul><li>Yongqiang Xue et. al, “Fermi-Level Alignment at Metal-Carbon Nanotube Interfaces: Application to Scanning Tunneling Spectroscopy”, Physical Review Letters, 83(23), 4844-4847 (1999) </li></ul><ul><li>Quoc Ngo et al. “Electron Transport Through Metal–Multiwall Carbon Nanotube Interfaces”, IEEE Transactions on Nanotechnology, 3(2), 311-317 (2004) </li></ul><ul><li>Woong Kim et al., “Electrical contacts to carbon nanotubes down to 1 nm in diameter”, Applied Physics Letters, 87, 173101 (2005) </li></ul><ul><li>M. P. Anantram et al., “Which nanowire couples better electrically to a metal contact: Armchair or zigzag nanotube?,” Applied Physics Letters, 78, 2055–2057 (2001) </li></ul><ul><li>J. Tersoff, “Contact resistance of carbon nanotubes”, Applied Physics Letters, 74(15), 2122-2124 (1999) </li></ul>
    32. 32. References <ul><li>A. Bachtold et al., “Contacting carbon nanotubes selectively with low-ohmic contacts for four-probe electric measurements”, Applied Physics Letters, 73(2), 274-276 (1998) </li></ul><ul><li>A. Yu. Kasumov et al., “Conductivity and atomic structure of isolated multiwalled carbon nanotubes”, Europhysics Letters, 43(1), 89-94 (1998) </li></ul><ul><li>Philip G. Collins et al., “Current Saturation and Electrical Breakdown in Multiwalled Carbon Nanotubes”, Physical Reivew Letters, 86(14), 3128-3131 (2001) </li></ul><ul><li>Hongjie Die et al., “Probing electrical transport in nanomaterials: conductivity of individual carbon nanotubes”, Science, 272(5261), 523-526 (1996) </li></ul><ul><li>H. J. Li et al., “Multichannel ballistic transport in multiwall carbon nanotubes”, Physical Review Letters, 95(5), 086601 (2005) </li></ul><ul><li>Xin Guo et al., “Tunneling leakage current in oxynitride: dependence on oxygen/nitrogen content”, IEEE Electron Device Letters, 19(6), 207-209 (1998) </li></ul><ul><li>S.-H. lo et al., “Quantum-mechanical modeling of electron tunneling current from the inversion layer of ultra-thin-oxide nMOSFETs”, IEEE Electron Device Letters, 18(5), 209-211 (1997) </li></ul>

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