Chapter IV Results and discussions
4.2 Morphologies and Raman spectra of the carbon nanostructures
4.4.2 Low temperature growth mechanism
Hofmann et al. proposed the surface diffusion: The low activation energy path for nanotube growth [Hofmann-2005-036101], find low activation energy of 0.4 eV for carbon surface diffusion on Ni and Co (111) planes, much lower than for bulk diffusion. In MPCVD, the plasma ionizes the gas and creates new and more reactive species, such as radicals, in the gas phase and/or the catalyst surface, as well as to cause a local surface heating that enables an efficient adsorption and diffusion of carbon atoms at low substrate temperatures. The plasma atmosphere may influence the detailed catalyst surface kinetics in many ways and may also supply carbon from the gas phase for SWNTs growth. This allows a reduction of the growth activation energy, as, e.g., atomic carbon can chemisorb directly on the catalyst. Therefore, we suggest that diffusion of carbon on the catalyst surface is the rate determining step at low temperatures. The effect of the plasma is to increase the dissociation of CH4, and etch any a-C, which may deposit on top of the catalyst particle, thereby providing a steady supply of carbon atoms at the top surface of the catalyst particle. At low temperatures, the solubility of C in Co is low, so the amount of carbon diffusing through the particle is very limited. However, carbon atoms adsorbed at the top surface of the catalyst particle can diffuse along the surface, where their motion is much faster. Carbon then segregates at the bottom of the particle, forming graphitic planes. This process allows SWNTs to grow at such low temperatures.
Fig. 4.15 EDX analysis of as-grown SWNTs removed substrate.
4.5 Properties analyses of SWNTs 4.5.1 Field emission properties
The field emission current density as a function of electric field for the as-grown well-aligned SWNT of sample A5 (CoCrPtOx 1 nm) is shown in Fig.
4.16. It shows a turn on voltage of 4.6 V/μm (0.01 mA/cm2) and the current
density of 6 mA/cm2 (7.2 V/μm). In our experiments, the tube packing density is obviously higher and results in lower intertube distances. In order to avoid the field screening effect, a lower packing density of CNTs is favorable.
Fig. 4.16 Field emission current density as a function of electric field for the SWNTs
4.5.2 Oxidation resistance
Thermo-gravimetric analysis (TGA) is implemented on 5 mg of the as-grown SWNTs (ramp rate, 10°C/min in air, 30 sccm/min), as shown in Fig.
4.17. The combustion range of the SWNTs was 586°C to 691°C, with the peak weight reduction occurring at 650°C, a result very similar to that of purified, high-quality SWNTs synthesized by a laser-oven method. We believe that the small initial weight increase is due to physisorption,supported by the fact that the weight returns to its initial value by subsequent annealing. No measurable residue remained after heating above 700°C, indicating very high purity.
800.00 600.00
400.00 200.00
0.00 TGA
%
50.00
0.00 100.00
Temperature 0C
Fig. 4.17 Thermo-gravimetric properties of as-grown SWNTs. (5 mg, ramp rate, 10°C/min)
Chapter V Conclusions
In this work, the CoCrPtOx film was successfully used as catalyst precursor to grow the well-aligned SWNTs with high tube number density by MPCVD.
The main mechanism to form SWNTs is due to the fact that the PtOx in the CoCrPtOx precursor can be decomposed during pretreatment to promote miniaturization of the Co-catalyst particle due to explosive effect of the reaction.
Moreover, Cr2O3 in the precursor can act to separate the Co-catalyst nanoparticles from agglomeration. The process also takes the advantage of recycling the catalyst-coated substrate to minimize the processing cost.
These SWNTs exhibit competitive field emission properties, i.e. turn on voltage of 4.6 V/μm (at 0.01 mA/cm2) and the current density of 6 mA/cm2 (at 7.2 V/μm). Raman spectra indicate that the IG/ID ratio of these SWNTs can be reached to ~ 43, indicating a good quality. The results of TGA analysis in air show that these SWNTs can resist oxidation up to 586°C ~ 691°C, which are much higher than the reported temperatures (~ 350°C) in the literature, and are comparable with that for the purified SWNTs synthesized by a laser-oven method.
The scanning local laser heating pretreatment was successfully used to
decrease the CNTs deposition temperature to 373°C, which is based on heating the local area to a higher temperature to form nanoparticles and maintaining the substrate at lower temperature.
Chapter VI Future prospects
1. The effect of catalyst composition on SWNTs growth.
2. Feasibility study of SWNTs growth with higher length at large area.
3. Synthesize SWNTs on plastic substrate.
References B
1. Bachtold, A., P. Hadley, T. Nakanishi, and C. Dekker, Science, 294, (2001), 1317-1320, “Logic Circuits with Carbon Nanotube Transistors”.
2. Berber, Savas, Young-Kyun Kwon,* and David Tománek, PHYSICAL REVIEW LETTERS, 84, (2000), 4613-4616, “Unusually High Thermal Conductivity of Carbon Nanotubes”.
3. Bethune, D. S., Kiang C. H., Vries M. S. de, Gorman G., R. Savoy, J.
Vazquez, and R. Beyes, Nature, 363, (1993), 605-607, ”Cobalt- Catalysed growth of carbon nanotubes with single-atomic-layer wall”.
4. Baker, R. T. K. and P. S. Harris, in Chemistry and Physics of Carbon, edited by P. L. Walker and P. A. Thrower ~Marcel Dekker, New York, (1978), Vol. 14.
5. Birkett, P.R., A. J. Cheetham, B. R. Eggen, J. P. Hare, H. W. Kroto, Chemical Physics Letter, 281, (1997), 111-114,”Transition metal surface decorated fullerenes as possible catalytic agents for the creation of single walled nanotubes of uniform diameter”.
C
1. Collins, P. G., M. S. Arnold, and P. Avouris, Science, 292, (2001), 706-709,
“Engineering Carbon Nanotubes and Nanotube Circuits Using Electrical
Breakdown”.
2. Che, Jianwei, Tahir Cagın and William, Nanotechnology, 11, (2000), 65–69,
“A Goddard III Thermal conductivity of carbon nanotubes”.
3. Choi, W. B., Chung D. S., Kang J. H., Kim H. Y., Jin Y. W., Ha I. T., Y. H.
Lee, Jung J. E., Lee N. S., Park G. S., and Kim J. M., Appl. Phys. Lett., 75, (1999), 3129-3131, “Fully sealed, high-brightness carbon-nanotube field-emission display”.
D
1. Delzeit, L., B. Chen, A. Cassell, R. Stevens, C. Nguyen, and M. Meyyappan, Chem. Phys. Lett. 348, (2001), 368-374, Multilayered metal catalysts for controlling the density of single-walled carbon nanotube growth”.
2. Dresselhaus, M. S., G. Dresselhaus, P. C. Eklund, “Science of Fullerences and Carbon Nanotubes” (Academic Press, New York, 1996), P756.
3. Dai, H., A. G. Rinzler, P. Nikolaev, A. thess, D. T. Colber, and R. E. Smalle, Chem. Phys. Lett., 260, (1996), 471-475, ”Single-walled nanotubes produced by metal catalyzed disproportionation of carbon monoxide”.
4. Dresselhaus, M. S., G. Dresselhaus, A. Jorio, A.G. Souza Filho, R. Saito, R.
saito, carbon, 35, (2002), 2043–2061, “Raman spectroscopy on isolated single wall carbon nanotubes”.
5. Derycke, V., Martel R., Appenzeller J., and Ph. Avouris, Nano Letter, 1,
(2001), 453-456, “Carbon Nanotube Inter- and Intramolecular Logic Gates”.
6. Dai, H., Hafner J. H., Rinzler A. G., Colber D. T., and Smalley R. E., Nature, 384, (1996), 147-150, ”Nanotubes as nanoprobes in scanning probe microscopy”.
E
1. Eric W. Wong, Paul E. Sheehan, Charles M. Lieber, Science, 277, (1997), 1971-1975, “Nanobeam mechanics: Elasticity, strength, and toughness of nanorods and nanotubes”.
G
1. Groning O., O. M. Kuttel, Ch. Emmenegger, P. Groning, and L. Schlapbach, J. Vac. Sci. Technol. B, 18, (2000), 665-678, “Field emission properties of carbon nanotubes”.
2. Guo, T., P. Nikolaev, A. Thess, D. T. Colbert, and R. E. Smalley, Chem.
Phys. Lett., 243, (1995), 49-54, “Catalytic Growth of Single-walled Nanotubes by Laser Vaporization”.
3. Gavillet, J., A. Loiseau, C. Journet, F. Willaime, F. Ducastelle, and J.-C.Charlier, Physical Review Letters, 87, (2001), 275504-1 -275504-4,
“Root-Growth Mechanism for Single-Wall Carbon Nanotubes”.
4. Gorbunov, A., O. Jost , W. Pompe , A. Graff, Carbon, 40, (2002)
113–118, ”Solid–liquid–solid growth mechanism of single-wall carbon Nanotubes”.
5. Gao, B., A. Kieinhammes, X. P. Tang, C. Bower, L. Fleming, Y. Wu and O.
Zhou, Chem. Phys. Lett., 307, (1999), 153-157, “Electrochemical intercalation of single walled carbon nanotubes with lithium”
H
1. Hamada Noriaki, Shin-ichi Sawada, and Atsushi Oshiyama, Phy. Rev.
Letters, 68, (1992), 1579-1581, “New One-diamensional Conductors:
Graphitic Microtubules”.
2. Hofmann, S., G. Csanyi, A. C. Ferrari, M. C. Payne and J. Robertson, PHYSICAL REVIEW LETTERS, 95, (2005), 036101, “Surface Diffusion:
The Low Activation Energy Path for Nanotube Growth”
I
1. Iijima, S., Nature, 354, (1991), 56-58, ”Helical microtubules of graphitic carbon”
K
1. Kroto H.W., J.R. Heath, S.C. O’Brien, R.F. Curl & R.E. Smalley, Nature, 318, (1985), 162-163, “C60:Buckminsterfullerence”
2. Kim J., I. Hwang, D. Yoon, I. Park, D. Shin, T. Kikukawa, T. Shima, and J.
Tominaga, Appl. Phys. Lett., 83, (2003), 1701-1703, “Super- resolution by
elliptical bubble formation with PtOx and AgInSbTe layers”.
3. Kurt, R., J. M. Bonard, A. Karimi, Carbon, 39, (2001), 1723-1730,
“Morphology and field emission properties of nano-structured nitrogenated carbon films produced by plasma enhanced hot filament CVD”.
4. Kuo, C. T., T. K. Chao, “Nano-structured materials science” (Chwa technology books), (2004), P.9-10~P.9-14.
5. Kong J., A. M. Cassell, and H. Dai, Chem. Phys. Lett., 292, (1998), 567-574,
“Chemical vapor deposition of methane for single-walled carbon nanotubes”.
L
1. Kuo, Cheng Tzu, Chao Hsun Lin and An Ya Lo, Dia. Rel. Mat., 12, (2003), 799-805, “Feasibility studies of magnetic particle embedded carbon nanotubes for perpendicular recording media”.
2. Lee, C. J., S. C. Lyu, Y. R. Cho, J. H. Lee, and K. I. Cho, Chem. Phys. Lett., 341, (2001), 245-249, “Diameter-controlled growth of carbon nanotubes using thermal chemical vapor deposition”.
3. Lin, C. H., H. L. Chang and C. T. Kuo, Dia. Rel. Mater., 11, (2002), 922-926, “Growth meachanism and properties of the large area well-aligned carbon nanostructures deposited by microwave plasma ECRCVD”.
4. Liu, C., Y. Y. Fan, M. Lu, H. T. Cong, H. M. Cheng, M. S. Dresselhaus,
Science, 286, (1999), 1127-1129, “Hydrogen Storage in Single-Walled Carbon Nanotubes at Room Temperature”.
O
1. Odom Teri Wang, Jin-Lin Huang, Philip Kim and Charles M. Lieber, Nature, 391, (1998), 62-64, “Atomic structure and electronic properties of single-walled carbon nanotubes“.
P
1. Pan Z. W., S. S. Xie, L. Lu, B. H. Chang, L. F. Sun, W. Y. Zhou, G. Wang, and D. L. Zhang, Appl. Phys. Lett., 74, (1999), 3152-3154, “Tensile tests of ropes of very long aligned multiwall carbon nanotubes”.
Q
1. Qin, L. C., D. Zhou, A. R. Krauss, and D. M. Gruen, App. Phys. Lett., 72, (1998), 3437-3439, "Growing carbon nanotubes by microwave plasma-enhanced chemical vapor deposition".
R
1. Rao, A. M., E. Richter, Shunji Bandow, Bruce Chase,P. C. Eklund, K. A.
Williams, S. Fang, K. R. Subbaswamy,M. Menon, A. Thess, R. E. Smalley, G. Dresselhaus,andM. S. Dresselhaus, science, 275, (1997), 187-191,
“Diameter-Selective Raman Scattering from Vibrational Modes in Carbon Nanotubes”.
2. Raravikar, Nachiket R., Pawel Keblinski, Apparao M. Rao, Mildred S.
Dresselhaus, Linda S. Schadler and Pulickel M. Ajayan, PHYSICAL REVIEW B, 66, (2002), 235424-1~235424-9, “Temperature dependence of radial breathing mode Raman frequency of single-walled carbon
nanotubes”.
S
1. Shaijumon M. M., N. Bejoy, and S. Ramaprabhu, Appl. Sur. Sci., 242, 192, (2002), 192-198, “Temperature dependence of radial breathing mode Raman frequency of single-walled carbon nanotubes”.
2. Saito R., Fujita M., Dresselhaus G., and Dresselhaus M. S, Appl. Phys. Lett., 60, (1992), 2204-2206, “Electronic structure of chiral graphene tubules”.
3. Spindt, C. A., I. Bride, L. Humprey and E. R. Westerberg, ,J. Appl. Phys., 47, (1976), 5248, “ Physical properties of thin-film field emission cathodes molybdenum cones”
4. Satio, Y, Carbon, 33, (1995), 979-988, “Nanoparticles and filled nanocapsules”.
5. Saito, Yahachi, Mitsumasa Okuda, Naoya Fujimoto Tadanobu Yoshikawa, Masato Tomita, and Takavoshi Hayashi, Jpn. J. Appl. Phys, 33, (1994), L526-L529, ”Single-wall carbon nanotubes growing radially from Ni fine particles formed by arc evaporation”.
6. Saito, Y., S. Uemura, and K. Hamaguchi, Jpn. J. Appl. Phys., 37, (1998),
L346-348, “Cathode Ray Tube Lighting Elements with Carbon Nanotube Field Emitters”.
7. Sander, J. Tans, A. R. M. Verschueren, and C. Dekker, Nature, 393,
(1998), 49-52, “Room-temperature transistor based on a single carbon nanotube”.
T
1. Tsai, M. H., M.S. Thesis, (2001), Mat. Res. Lab., MSE, NCTU, “Deposition mechanisms and properties of large area well-aligned carbon nanotubes by catalyst-assisted ECR-CVD method”.
2. Thess, Andreas, Lee, Roland, Nikolaev, Pavel, Dai, Hongjie, Science, 273, (1996), 483-487, “Crystalline ropes of metallic carbon nanotubes”.
3. Tuinstra, F., and J. L. Koenig, The journal of chemical, 53, (1970), 1126-1130, “Raman Spectrum of Graphite”.
W
1. Wildoer, Jeroen W. G., Liesbeth C. Venema, Andrew G. Rinzler†, Richard E. Smalley and Cees Dekker, 391, (1998), 59-62, “Electronic structure of atomically resolved carbon nanotubes”.
2. Wong, S. S., E. Joselevich, A. T. Woolley, C. L. Cheung, C. M. Lieber, Nature, 394, (1998), 52-55, “Covalently functionalized nanotubes as nanometre-sized probes in chemistry and biology”.
3. W.H. Wang, Y.R. Peng, C.T. Kuo, Diamond & Related Materials, (2006),
“Low temperature growth mechanism of SWNTs networks by buffer layer assisted MPCVD”.
4. W.H. Wang, Y.R. Peng, C.T. Kuo, Diamond & Related Materials, 14, (2005), 1906-1910, “Effects of buffer layer materials and process conditions on growth mechanisms of forming networks of SWNTs by microwave plasma chemical vapor deposition”.
Y
1. Yu, M, O. Lourie, M. Dyer, K. Mooni, T. Kelly, R. S. Ruoff, Science, 287, (2000), 637-640, “Strength and Breaking Mechanism of Multiwalled Carbon Nanotubes Under Tensile Load”.
2. Yun Sung Woo, Duk Young Jeon, In Taek Han, Young Jun Park, Ha Jin Kim, Jae Eun Jung, Jong Min Kim, Nae Sung Lee, J. of Appl. Phy., 94, (2003), 6789-6795, “Structural characteristics of carbon nanorods and nanotubes grown using electron cyclotron resonance chemical vapor deposition”.
3. Yue G. Z., Q. Qiu, Bo Gao Y. Cheng, J. Zhang, H. Shimoda, S. Chang, J. P.
Lu and O. Zhou, Appl. Phys. Lett., 81, (2002), 355-357, “Generation of continuous and pulsed diagnostic imaging x-ray radiation using a carbon-nanotube-based field-emission cathode”.
Z
1. Zhong G., T. Iwasaki, K. Honda, Y. Furukawa, I. Ohdomari, and H.
Kawarada, Jpn. J. Appl. Phys. 44, (2005), 1558-1561, “Low Temperature Synthesis of Extremely Dense and Vertically Aligned Single-Walled Carbon Nanotubes”.
2. Zhou Dan and Su Wang, Appl. Phys. Lett., 65, (1994), 1593-1595,
“Single-walled carbon nanotubes growing radially from YC2 particles”.