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Hyo-Shin Ahn * , Seungwu Han † , Do Yeon Kim § , Kwang-Ryeol Lee

Enhanced Growth and Field Emission of Carbon Nanotube by Nitrogen Incorporation: The First Principle Study. Hyo-Shin Ahn * , Seungwu Han † , Do Yeon Kim § , Kwang-Ryeol Lee Future Technology Research Division, KIST, Seoul, Korea

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Hyo-Shin Ahn * , Seungwu Han † , Do Yeon Kim § , Kwang-Ryeol Lee

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  1. Enhanced Growth and Field Emission of Carbon Nanotube by Nitrogen Incorporation: The First Principle Study Hyo-Shin Ahn*, Seungwu Han†, Do Yeon Kim§, Kwang-Ryeol Lee Future Technology Research Division, KIST, Seoul, Korea * Presently at Center for Strongly Correlated Materials Research, Seoul National University, Seoul, Korea † Department of Physics, Ehwa Women’s University, Seoul, Korea § Department of Materials Science, Seoul National University, Seoul, Korea

  2. Enhanced Growth and Field Emission of Carbon Nanotube by Nitrogen Incorporation: The First Principle Study Hyo-Shin Ahn*, Seungwu Han†, Do Yeon Kim§, Kwang-Ryeol Lee Future Technology Research Division, KIST, Seoul, Korea * Presently at Center for Strongly Correlated Materials Research, Seoul National University, Seoul, Korea † Department of Physics, Ehwa Women’s University, Seoul, Korea § Department of Materials Science, Seoul National University, Seoul, Korea

  3. CNT Growth by CVD H2, Ar, N2, NH3 40㎚

  4. 300nm CNT Growth by Thermal CVD at 950℃ with 16.7 vol. % C2H2 in pure NH3 at 950℃ with 16.7 vol. % C2H2 in N2:H2 = 1:3 M.-J. Jung et al, Diam. Rel. Mater. 10, 1235 (2001).

  5. T.Y. Kim et al, Chem. Phys. Lett. 372, 603 (2003).

  6. N with sp2 C N in sp3 environ. Nitrogen Incorporation into CNTs XPS EELS W.-Q. Han et al, Appl. Phys. Lett. 77, 1807 (2000). Kim et al, Chem. Phys. Lett. 372, 603 (2003)

  7. Nitrogen Incorporation into CNTs Nitrogen incorporation significantly enhances the CNT growth resulting in vertically aligned CNTs. 16.7 vol. % C2H2 in NH3, CVD process What is the effect of the incorporated nitrogen?

  8. Enhanced CNT Growth by Nitrogen Incorporation Ab-initio Study of Nitrogen Effect on Carbon Nanotube Growth, Nanotechnology, 17, 909-912 (2006).

  9. CNT-FED by Samsung Field Emission from CNT CNT is a strong candidate for field emission cathode materials 1. Long aspect ratio : Highly enhanced electric field 2. Materials property Low turn-on voltage What’s the effect of nitrogen?

  10. (5,5) Caped CNT, 250atoms Localized basis • Ab initio tight binding calc. To obtain self-consistent potential and initial wave function • Relaxation of the wave function • Basis set is changed to plane wave to emit the electrons • Time evolution • Evaluation of transition rate by time dependent Schrödinger equation Plane wave Calculation Method S. Han et al., PRB, 66, 241402 (2002).

  11. Energy states (eV, E-EF) A B C D Emitted current(μA) Emission from Pure CNT Cutoff radius 80Ry, Electric field at the tip 0.7V/Å Band selection : E-Ef= -1.5eV ~ 0.5V

  12. A State C state D state B State Energy states (eV, E-EF) A B C D Emitted current(μA) Emission from Pure CNT

  13. Emission from Pure CNT S. Han et al., PRB, 66, 241402 (2002).

  14. Emission from N doped CNT Cutoff radius 80, Electric field at the tip 0.7V/Å Band selection : E-Ef= -1.5eV ~ 0.5V Energy states (eV, E-EF) A B C D Emitted current(μA)

  15. Nitrogen doped CNT Pure CNT Energy states (eV, E-EF) Energy states (eV, E-EF) Emitted current(μA) Emitted current(μA) Total current: 13.2mA Total current: 8.8mA Enhanced Field Emssion by Nitrogen Incorporation A B C D

  16. Emission from N doped CNT Cutoff radius 80, Electric field at the tip 0.7V/Å Band selection : E-Ef= -1.5eV ~ 0.5V Energy states (eV, E-EF) A B C D B A Emitted current(μA) D C

  17. Emission from N doped CNT B state D state C state A state πbond: Extended state π*+localized state Localized state Hybridized states of the localized and the extended states contribute to the field emssion.

  18. Localized state - Undoped CNT - N-doped CNT EF Doped Nitrogen Position Nitrogen Effect The nitrogen has lower on-site energy than that of carbon atom. T. Yoshioka et al, J. Phys. Soc. Jpn., Vol. 72, No.10, 2656-2664 (2003). The lower energy of the localized state makes it possible for more electrons to be in the localized states.

  19. N B Experimental Results L.H.Chan et al., Appl. Phys. Lett..82, 4334 (2003).

  20. Boron Doped CNT BORON DOPED NITROGEN DOPED Doped Atom Position

  21. Field Emission from N-doped CNT • Nitrogen incorporating enhances the field emission of CNT. • In addition to localized state, hybrid states of the extended and the localized states play a significant role. • Incorporated nitrogen lowers the energy level of the localized state, which makes electrons more localized to the tip of nanotube. H. S. Ahn et al., Appl. Phys. Lett. 88, 093122 (2006).

  22. Acknowledgement • Financial support from Core Capability Enhancement Program of KIST.

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