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 Ahn1,2, Seung-Cheol Lee1, Seungwu Han3,
Kwang –Ryeol Lee1 and Doh-Yeon Kim2
1 Korea institute of science and technology2 Department of materials science and engineering, Seoul national university
3 Department of physics, Ehwa womans university
CNT Growth by CVDCNT Growth by CVD
Vertically aligned multi-wall CNT Chemical Physics Letters, Vol. 372, 603(2003)
Tangled CNTC2H2+H2600~900
Tangled CNTC2H2+H2, C2H2+N2950
Tangled CNTC2H2+H2, C2H2+N2850
method
ferrocene+xylene
CH4+H2
CH4+N2
CH4+N2
C2H2+Ar
C2H2+NH3
C2H2+NH3
C2H2+NH3
C2H2+NH3
C2H2+NH3
C2H2+NH3
C2H2+NH3
C2H2+NH3
C2H2+NH3
C2H2+NH3
Reaction Gas CatalystTemperatue(oC)
APL 77 3764 (2000)Aligned CNTFe800 Thermal-CVD
APL 76 2367 (2000)Aligned CNTNi700 PE-CVD
JAP 89 5939 (2001)Aligned CNTFe550 PE-CVD
APL 75 3105 (1999)Aligned CNTFe, Ni500 PE-CVD
APL 75 1721 (1999)Tangled CNTNi, Co850~900Thermal-CVD
APL 80 4018 (2002)Aligned CNTNi660< PE-CVD
JAP 91 3847 (2002)Aligned CNT
Ni800~900
Thermal-CVD
DRM 10 1235 (2001)Aligned CNT
Ni950
Thermal-CVD
TSF 398-399 150 (2001)Aligned CNT
Ni, Co950
Thermal-CVD
APL 78 901 (2001)Aligned CNTFe800 Thermal-CVD
APL 77 2767 (2000)Aligned CNTCo825 PE-CVD
APL 77 3397 (2000)Aligned CNTFe750~950Thermal-CVD
APL 77 830 (2000)Aligned CNTCo825 PE-CVD
APL 75 1086 (1999)Aligned CNTNi660 PE-CVD
Science 282, 1105 (1998)Aligned CNTNi666PE-CVD
CitationCNT MorphologySynthesis condition
Nitrogen effect in CNT fabricationNitrogen effect in CNT fabrication
Molecular nitrogenor
without nitrogen
Tangled CNT
Atomic nitrogen
Aligned CNT
Process condition
NH3 decompositionN2 decomposition in plasma
H2, Ar, N2, NH3
Ambient gas affects the growth of carbon nanotubes
Growth rate increases as the nitrogen concentration in microwave plasmaJ. Lee, and B. Lee, Thin Solid Films, 418, 85-88 (2002)
Vertically aligned multi-wall CNT due to high growth rateChemical Physics Letters, Vol. 372, 603(2003)
CNT growth in nitrogen atmosphereCNT growth in nitrogen atmosphere
Calculation of Growth KineticsCalculation 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.
reactant product
Zigzag Edge Armchair Edge
Growth kinetics of nanotubeGrowth kinetics of nanotube
Ener
gy (a
rb. u
nit)
176 meV
tetragon pentagonhexagon
Growth reaction on zigzag edgeGrowth reaction on zigzag edge
Reaction
Total energy for the zigzag edge growth is 176meV
Growth reaction on armchair edgeGrowth reaction on armchair edge
pentagonhexagon
160 meV
64 meV
Reaction
Ener
gy (a
rb. u
nit)
The zigzag edge growth is rate determining in undoped CNT.
137meV
64meVNitrogen incorporation
~70meV
Pure C
pentagon hexagon
No significant change by nitrogen incorporation.
137meV
64meV
160meV
Reaction
Ener
gy (a
rb. u
nit)
160meV
Growth reaction incorporating nitrogen on armchair edgeGrowth reaction incorporating nitrogen on armchair edge
154meV
~26meVPure C
Nitrogen incorporation
tetragon pentagonhexagon
150 meV
176 meV
Nitrogen incorporation lowers kinetic barrier by ~26meV.
Reaction
Ener
gy (a
rb. u
nit)
152meV
No barrier
Growth reaction incorporating nitrogen on zigzag edgeGrowth reaction incorporating nitrogen on zigzag edge
No barrier
152meV 87meV
179meV 96meVNitrogen at top site
Pure C
pentagon hexagon
Nitrogen at valley site
No characteristic nitrogen effect on growth of armchair edge.
64meV
152meV160meV
179meV
96meV
87meV
Reaction
Ener
gy (a
rb. u
nit)
Growth reaction on nitrogen incorporated armchair edgeGrowth reaction on nitrogen incorporated armchair edge
No barrier
No barrierNo barrier No barrier
Pure C
Nitrogen in valley site
tetragon pentagonhexagon
333meV
Nitrogen in top site
No barrier
176meV
333meV
Nitrogen at valley site makes reaction difficult. However, nitrogen at top site eliminates the kinetic barrier for the growth.
No barrier
Reaction
Ener
gy (a
rb. u
nit)
Growth reaction on nitrogen incorporated zigzag edgeGrowth reaction on nitrogen incorporated zigzag edge
Near the nitrogen incorporated region (top site), the activation energy for carbon growth disappears.
No barrier
Energ
y
growth of C
tetragon pentagonhexagon
growth near the nitrogen incorporated region.
No barrier
No barrier
176 meV
Growth reaction on nitrogen incorporated zigzag edgeGrowth reaction on nitrogen incorporated zigzag edge
electronic structureelectronic structure
Eb=176meV
Eb=0meV
When nitrogen locates in the hexagon network, lone pair (localized) electrons around the nitrogen atom make weak bonds
weaker bond
ConclusionConclusion
In pure carbon systemArmchair 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.