In-situ X-ray Photoelectron Spectroscopy Study of Catalyst−Support Interactions and Growth of Carbon Nanotube Forests

Mattevi, Cecilia; Wirth, Christoph; Hofmann, Stephan; Blume, Raoul; Cantoro, Mirco; Ducati, Caterina; Cepek, Cinzia; Knop‐Gericke, Axel; Milne, Simon; Castellarin‐Cudia, Carla; Dolafi, Sheema; Goldoni, A.; Schlögl, Robert; Robertson, John

doi:10.1021/jp802474g

Cited by 248 publications

(278 citation statements)

References 56 publications

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“…From our experience we know that at high growth temperatures catalyst particles become rather large [33]. The enlargement in the particle size is most likely due to fact that at high temperatures, metal oxide loses its oxygen and becomes elemental; a catalyst metal without oxygen, especially on a SiO 2 surface, coalesces more easily and forms larger nanoparticles [4]. However, larger particles are less effective in catalyzing nanotubes [33].…”

Section: Resultsmentioning

confidence: 99%

“…The Ar flow was kept constant at 120 sccm until the given growth temperature was reached. The samples were subjected to H 2 pretreatment at 120 sccm before introducing CH 4 . Flow rate of the gases was controlled by electronic mass flow meters.…”

Section: Methodsmentioning

confidence: 99%

“…It has been shown that CNTs grown on aluminum oxide (Al 2 O 3 ) with Fe a few nanometers thick in ethylene CVD yield densely populated and vertically aligned CNTs [4]. However, direct growth on SiO 2 /Si is very important since it allows integration of CNTs with microelectronics technology and opens the possibility of ben-efiting from already very advanced silicon processing technology [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…Another work reported that hydrogen radicals can have deleterious effects on Single Walled CNTs (SWNT) growth by plasma enhanced CVD, etching away grown NT structures and hence, hindering the growth process [18]. This study reported that when only H 2 was added to CH 4 that CNTs grew to be only scarcely populated. In this report it was claimed that oxygen was needed in addition to H 2 for a vertically aligned growth, which annihilated the effects of H 2 before it destroyed the tubular structure.…”

Section: Introductionmentioning

confidence: 99%

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Carbon nanotube diameter tuning using hydrogen amount and temperature on SiO2/Si substrates

Aksak

Selamet

2010

Appl. Phys. A

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Carbon nanotubes (CNTs) were grown on thin iron (Fe) films on SiO 2 /Si substrates by chemical vapor deposition (CVD) at four different hydrogen (H 2 )/methane (CH 4 ) ratios at temperatures ranging from 925 to 1000°C. The effects of temperature and the amount of hydrogen gas on the mean diameter at increasing temperature were examined. We demonstrated that the mean diameter and its distribution depend not only on temperature but also on the H 2 amount. We showed that increasing H 2 amount strongly affects the structure of CNTs, especially at high growth temperature; the mean diameter at 1000°C reduced from about 383 to 34 nm by increasing H 2 amount from 24 to 50 sccm. We observed that at high temperature growth the mean diameter was decreasing very fast initially with increasing H 2 amount suggesting the dominance of H 2 over the growth temperature. A decrease in the slope of diameter vs. H 2 amount with further increment in H 2 amount implied that the temperature was, then, deciding the CNT diameter through catalyst particle coarsening. The statistical analysis presented implies that the H 2 amount has to be adjusted according to the growth temperature for given CH 4 amount to keep CNT diameter under control, and the large diameter distributions at high temperature and high H 2 amount can be associated with the large variation in the catalyst particle sizes.M. Aksak · Y. Selamet ( ) Carbon

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Carbon nanotube diameter tuning using hydrogen amount and temperature on SiO2/Si substrates

Aksak

Selamet

2010

Appl. Phys. A

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“…[5][6][7][8][9][10] It has been claimed that Fe/Al 2 O 3 interfacial bonding restricts Fe surface mobility and hence allows for high density SWCNT forest growth. 5,6 In addition, it has been suggested 7,8 that Al 2 O 3 , which is a well known catalyst for hydrocarbon formation, 11 aids in decomposing the carbon precursor and therefore enhances SWCNT forest growth from the catalyst. This suggestion, however, has been rejected by Mattevi et al 6 In addition, the morphology of the substrate has been proven to play an important role in the behavior of the catalyst, 9,10 and therefore determines whether or not a SWCNT forest is grown.…”

Section: Catalytic Chemical Vapor Deposition (Cvd) Is Currently the Mmentioning

confidence: 99%

X-ray photoelectron spectroscopy study on Fe and Co catalysts during the first stages of ethanol chemical vapor deposition for single-walled carbon nanotube growth

Oida

McFeely

Bol

2011

Journal of Applied Physics

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Optimized chemical vapor deposition processes for single-walled carbon nanotube (SWCNT) can lead to the growth of dense, vertically aligned, mm-long forests of SWCNTs. Precise control of the growth process is however still difficult, mainly because of poor understanding of the interplay between catalyst, substrate and reaction gas. In this paper we use x-ray photoelectron spectroscopy (XPS) to study the interplay between Fe or Co catalysts, SiO2 and Al2O3 substrates and ethanol during the first stages of SWCNT forest growth. With XPS we observe that ethanol oxidizes Fe catalysts at carbon nanotube (CNT) growth temperatures, which leads to reduced carbon nanotube growth. Ethanol needs to be decomposed by a hot filament or other technique to create a reducing atmosphere and reactive carbon species in order to grow vertically aligned single-walled carbon nanotubes from Fe catalysts. Furthermore, we show that Al2O3, unlike SiO2, plays an active role in CNT growth using ethanol CVD. From our study we conclude that metallic Fe on Al2O3 is the most optimal catalyst/substrate combination for high-yield SWCNT forest growth, using hot filament CVD with ethanol as the carbon containing gas.

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Application of Ambient‐Pressure X‐ray Photoelectron Spectroscopy for the In‐situ Investigation of Heterogeneous Catalytic Reactions

Starr

Bluhm

et al. 2013

In‐situ Characterization of Heterogeneous Catalysts

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Heterogeneous chemical reactions at vapor/solid interfaces play an important role in many processes in the environment and technology. Ambient pressure X-ray photoelectron spectroscopy (APXPS) is a valuable tool to investigate the elemental composition and chemical specificity of surfaces and adsorbates on the molecular scale at pressures of up to 130 mbar. In this review we summarize the historical development of APXPS since its introduction over forty years ago, discuss different approaches to minimize scattering of electrons by gas molecules, and give a comprehensive overview about the experimental systems (vapor/solid interfaces) that have been studied so far. We also present several examples for the application of APXPS to environmental science, heterogeneous catalysis, and electrochemistry.

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In-situ X-ray Photoelectron Spectroscopy Study of Catalyst−Support Interactions and Growth of Carbon Nanotube Forests

Cited by 248 publications

References 56 publications

Carbon nanotube diameter tuning using hydrogen amount and temperature on SiO2/Si substrates

Carbon nanotube diameter tuning using hydrogen amount and temperature on SiO2/Si substrates

X-ray photoelectron spectroscopy study on Fe and Co catalysts during the first stages of ethanol chemical vapor deposition for single-walled carbon nanotube growth

Application of Ambient‐Pressure X‐ray Photoelectron Spectroscopy for the In‐situ Investigation of Heterogeneous Catalytic Reactions

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