First principles calculation on nitrogen effect on the growth of carbon nanotube 2004.11.30....

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


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


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


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.

First principles calculation on nitrogen effect on the growth of carbon nanotube 2004.11.30....

Documents

Transcript of First principles calculation on nitrogen effect on the growth of carbon nanotube 2004.11.30....