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First principles calculation on nitrogen effect on the growth of carbon nanotube

First principles calculation on nitrogen effect on the growth of carbon nanotube. 2004.11.30. Hyo-Shin Ahn 1,2 , Seung-Cheol Lee 1 , Seungwu Han 3 , Kwang –Ryeol Lee 1 and Doh-Yeon Kim 2 1 Korea institute of science and technology

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First principles calculation on nitrogen effect on the growth of carbon nanotube

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  1. First principles calculation on nitrogen effect on the growth of carbon nanotube 2004.11.30. Hyo-Shin Ahn1,2, Seung-Cheol Lee1, Seungwu Han3, Kwang –Ryeol Lee1 and Doh-Yeon Kim2 1 Korea institute of science and technology 2 Department of materials science and engineering, Seoul national university 3 Department of physics, Ehwa womans university

  2. CNT Growth by CVD Vertically aligned multi-wall CNT Chemical Physics Letters, Vol. 372, 603(2003)

  3. Synthesis condition CNT Morphology Citation method Temperatue(oC) Reaction Gas Catalyst PE-CVD 666 C2H2+NH3 Ni Aligned CNT Science 282, 1105 (1998) PE-CVD 660 C2H2+NH3 Ni Aligned CNT APL 75 1086 (1999) H2, Ar, N2, NH3 PE-CVD 825 C2H2+NH3 Co Aligned CNT APL 77 830 (2000) Process condition Thermal-CVD 750~950 C2H2+NH3 Fe Aligned CNT APL 77 3397 (2000) PE-CVD 825 C2H2+NH3 Co Aligned CNT APL 77 2767 (2000) NH3 decomposition N2 decomposition in plasma Thermal-CVD 800 C2H2+NH3 Fe Aligned CNT APL 78 901 (2001) Thermal-CVD 950 C2H2+NH3 Ni, Co Aligned CNT TSF 398-399 150 (2001) 850 C2H2+H2, C2H2+N2 Tangled CNT Thermal-CVD 950 C2H2+NH3 Ni Aligned CNT DRM 10 1235 (2001) Molecular nitrogen or without nitrogen 950 C2H2+H2, C2H2+N2 Tangled CNT Atomic nitrogen Thermal-CVD 800~900 C2H2+NH3 Ni Aligned CNT JAP 91 3847 (2002) 600~900 C2H2+H2 Tangled CNT PE-CVD 660< C2H2+NH3 Ni Aligned CNT APL 80 4018 (2002) Thermal-CVD 850~900 C2H2+Ar Ni, Co Tangled CNT APL 75 1721 (1999) PE-CVD 500 CH4+N2 Fe, Ni Aligned CNT APL 75 3105 (1999) Aligned CNT PE-CVD 550 CH4+N2 Fe Aligned CNT JAP 89 5939 (2001) Tangled CNT PE-CVD 700 CH4+H2 Ni Aligned CNT APL 76 2367 (2000) Thermal-CVD 800 ferrocene+xylene Fe Aligned CNT APL 77 3764 (2000) Nitrogen effect in CNT fabrication Ambient gas affects the growth of carbon nanotubes

  4. CNT growth in nitrogen atmosphere Vertically aligned multi-wall CNT due to high growth rate Chemical Physics Letters, Vol. 372, 603(2003) Growth rate increases as the nitrogen concentration in microwave plasma J. Lee, and B. Lee, Thin Solid Films, 418, 85-88 (2002)

  5. reactant product Calculation of Growth Kinetics • Kinetic barrier calculation by DMol3 for each reaction step. • Assumptions • Flat graphitic plate represents the large radius (~over 10nm in radius) CNTs. • Reduction of the kinetic barrier by the catalyst is not affected by the existence of nitrogen.

  6. Growth kinetics of nanotube Zigzag Edge Armchair Edge

  7. Growth reaction on zigzag edge Energy (arb. unit) 176 meV hexagon tetragon pentagon Reaction Total energy for the zigzag edge growth is 176meV

  8. 160 meV 64 meV hexagon pentagon Growth reaction on armchair edge Energy (arb. unit) Reaction The zigzag edge growth is rate determining in undoped CNT.

  9. Growth reaction incorporating nitrogen on armchair edge 137meV 160meV 64meV Nitrogen incorporation Pure C Energy (arb. unit) 137meV 160meV ~70meV 64meV hexagon pentagon Reaction No significant change by nitrogen incorporation.

  10. Growth reaction incorporating nitrogen on zigzag edge 152meV No barrier No barrier 154meV 176 meV Energy (arb. unit) Nitrogen incorporation ~26meV Pure C 150 meV hexagon tetragon pentagon Reaction Nitrogen incorporation lowers kinetic barrier by ~26meV.

  11. Growth reaction on nitrogen incorporated armchair edge 152meV 87meV 179meV 96meV Nitrogen at top site 179meV Energy (arb. unit) Nitrogen at valley site 160meV Pure C 96meV 152meV 87meV 64meV hexagon pentagon Reaction No characteristic nitrogen effect on growth of armchair edge.

  12. Growth reaction on nitrogen incorporated zigzag edge No barrier 333meV No barrier No barrier No barrier No barrier 333meV Nitrogen in valley site Energy (arb. unit) Nitrogen in top site 176meV Pure C No barrier hexagon tetragon pentagon Reaction Nitrogen at valley site makes reaction difficult. However, nitrogen at top site eliminates the kinetic barrier for the growth.

  13. Growth reaction on nitrogen incorporated zigzag edge No barrier No barrier growth near the nitrogen incorporated region. growth of C Energy 176 meV No barrier hexagon tetragon pentagon Near the nitrogen incorporated region (top site), the activation energy for carbon growth disappears.

  14. electronic structure weaker bond Eb=0meV Eb=176meV When nitrogen locates in the hexagon network, lone pair (localized) electrons around the nitrogen atom make weak bonds

  15. Conclusion In pure carbon system Armchair edge grows faster, then growth on zigzag edge is rate determining step. Nitrogen incorporation/Incorporated nitrogen effect on carbon attachment With nitrogen, the energy barrier for the zigzag edge growth becomes lower than that of armchair edge. - rate determining step is the growth of armchair edge. Nitrogen enhances the growth by lowering the kinetic barrier.

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