Data-driven understanding of collective carbon nanotube growth by in situ characterization and nanoscale metrology


Aligned carbon nanotubes (CNTs) possess great potential for transforming the fabrication of advanced interfacial materials for energy and mass transport as well as for structural composites. Realizing this potential, however, requires building a deeper understanding and exercising greater control on the atomic scale physicochemical processes underlying the bottom-up synthesis and self-organization of CNTs. Hence, in situ nanoscale metrology and characterization techniques were developed for interrogating CNTs as they grow, interact, and self-assemble. This article presents an overview of recent research on characterization of CNT growth by chemical vapor deposition (CVD), organized into three categories based on the growth stage, for which each technique provides information: (I) catalyst preparation and treatment, (II) catalytic activation and CNT nucleation, and (III) CNT growth and termination. Combining all three categories together provides insights into building the process–structure relationship, and paves the way for producing tailored CNT structures having desired properties for target applications.


Aligned carbon nanotubes (CNT), referred to as CNT forests, have repeatedly been shown to possess great potential for transforming the fabrication of thermal interfaces, electrical interconnects, nanoporous membranes, and structural fibers/composites.1,2 However, realizing this potential has proven to be challenging. A major challenge that hinders the successful integration of functional aligned CNTs into applications is the need for building the process–structure–property relationship that governs the fabrication of tailored CNTs by chemical vapor deposition (CVD). Here, what is referred to as “process” encompasses the catalyst preparation, catalytic activation, growth and deactivation steps of CNT growth by CVD. Importantly, CVD is a promising CNT fabrication method owing to its scalability, flexibility and the high quality of CVD-grown CNTs,3,4 but a comprehensive understanding of the whole CVD process is still largely missing. The “structure” refers to the morphology of the individual CNTs, and their organization into the vertically aligned forest morphology, including their diameter distribution, number of walls, alignment, defects, deformation, and density. Finally, the “property” here focuses on the collective properties of the CNT forest structure as a whole, in contrast to the properties of individual CNTs.

Studying how the morphology evolves during the successive stages of CNT growth by CVD from substrate bound catalyst nanoparticles has shown that a typical CNT forest exhibits spatial variations of diameter, alignment, and density, as shown schematically in Fig. 1.58 These variations arise from the dynamics of growth, which are dominated by time-varying kinetics of chemical decomposition, catalytic activation, catalyst poisoning/deactivation, and atomic diffusion.916 Importantly, the non-uniform morphology of CNT forests influences their properties, such as in mechanical compression for example, which was shown to be affected by density gradients.17 Hence, revealing the process–structure and structure–property relationships requires a comprehensive understanding of the atomic scale physicochemical processes underlying the bottom-up synthesis and self-organization of aligned CNTs. To that end, a large number of in situ nanoscale metrology and characterization techniques were explored over the past two decades for interrogating a large number of individual CNTs simultaneously as they grow, interact with each other, and self-assemble into the aligned morphology.

FIG. 1

Schematic showing the successive stages of the collective CNT growth mechanism, organized into three categories: (I) Catalyst preparation and treatment; (II) Catalytic activation and CNT nucleation; and (III) CNT growth and termination.

Many model-based efforts toward understanding CNT growth and termination have relied on one type of data such as the evolution of the forest height as a function of growth time for example, and used these kinetics to explain the behavior expected of a single CNT growing from a single catalyst nanoparticle. An inherent assumption in those studies is that the areal density of CNTs is uniform throughout the forest. However, data-driven approaches enabled by collecting more measurements of the spatiotemporal evolution of CNT morphology during growth revealed that a growing CNT forest behaves as a large population with a time-varying distribution of diameters, tortuosity, and density.5,7,8 Moreover, the interactions among growing CNTs play an important role in creating the self-supporting aligned morphology, as well as in the eventual growth self-termination.5,18

In a typical CNT forest, billions of CNTs grow simultaneously per square centimeter and interact together as they collectively build the vertically aligned structure. As shown in Fig. 1, this collective growth process can be broken down to a number of successive stages that are herein lumped into three main categories: (I) Catalyst preparation and treatment, in which the seeding nanoparticles are created by a combination of thin film deposition and thermal/chemical treatment for dewetting into a population of nanoparticles; (II) Catalytic activation and CNT nucleation, in which the introduction of the hydrocarbon gas leads to catalytic surface reactions and the formation of arranged carbon atoms on the surface of the catalyst nanoparticles that form a cap, leading to the lift-off of a population of CNTs that interact together; and (III) CNT growth and self-termination, in which the growth proceeds after CNT crowding and self-organization until the density starts to decay leading to eventual growth self-termination.


In most cases catalyst nanoparticles for CNT forest growth are prepared by annealing a thin film deposited by a physical vapor deposition (PVD) technique such as sputtering or electron beam evaporation. Annealing the as-deposited film causes dewetting (also referred to as agglomeration), by which a population of nanoparticles are created by atomic surface diffusion at high temperature.19 Although other methods of preparing the catalyst nanoparticles such as by optical and electron beam lithography,20 colloidal self-assembly,21,22 and block copolymer self-assembly23 have been used to successfully grow CNTs, thin film dewetting remains the most common, owing to its simplicity, ease of integration with CNT processing, and its scalability.

A number of transition metal catalysts, and combinations thereof, were used to grow CNTs including Ni, Fe, Mo, Co, and others.4,21,2426 Also, a number of different materials were used as a buffer layer between the metal catalyst and the substrate (usually a Si wafer), such as Al, Al2O3, TiN, and TiO2.27 It was shown that the catalyst–substrate interactions dictated the chemical changes that the as-deposited iron catalyst undergoes on different buffers upon exposure to C2H2. In particular, high growth rate of small-diameter CNTs was observed from FeO on Al2O3 buffer, as opposed to the slow growth of large CNTs having thick walls on both TiN and TiO2 buffers. Moreover, for the same buffer layer material aluminum oxide, different processing routes and film properties were shown to significantly influence CNT growth.15 Over the years, many approaches were explored for modifying the catalyst to improve growth. For example, growth was prolonged by tuning the stoichiometry of bimetallic catalyst particles, such as Ni–Fe,28 and Co–Mo.29 In another study, the stability of the support (aluminum oxide) layer was improved by doping with Lanthanum (La),30 which enabled growing CNT forests as high as 18 mm.31 Recently, ion bombardment was used to modify the surface properties for CNT growth.32

It’s noteworthy that the catalyst nanoparticle could act as a seed for CNT growth while remaining strongly bound to the substrate surface, in which case the growth is referred to as base-growth. On the other hand, if the catalyst nanoparticle is pushed upwards by the growing CNT, it is referred to as tip-growth, as has been shown for some Mo- and Co-containing catalysts.33 In cases of strong interactions between the active catalyst nanoparticles and the underlying support layer, such as between iron and aluminum oxide, base-growth is the dominant mechanism.15,34 Moreover, the growth mechanism was shown to shift between tip growth and base growth based on the diameter of the catalyst nanoparticle.35 Previously, backscatter-electron imaging was used to show that there are no traces of metal nanoparticles on the top of grown CNT forests,36 to confirm the base-growth process for Fe nanoparticle catalysts on aluminum oxide support layers. The rest of this article will focus on studying this catalyst system.

Film restructuring of the iron/aluminum oxide system was studied previously by a number of surface characterization techniques, such as scanning electron microscopy (SEM), atomic force microscopy (AFM), electron diffraction (ED), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and in situ grazing incidence small angle X-ray scattering (GI-SAXS).7,15,27,3743 Many imaging and chemical characterization techniques such as electron microscopy and XPS are typically difficult to employ in situ owing to the stringent requirements of low pressure, and limitations on the gases that can be introduced into the measurement chamber. On the other hand, scattering-based methods such as GI-XRD and GI-SAXS provided unique information on the morphology and chemical state of the catalyst during the preparation steps at higher pressures.

Environmental transmission electron microscopy (E-TEM) was recently used, as shown in Fig. 2, for the real-time observation of the collective process of catalyst nanoparticle preparation, CNT nucleation and eventual catalytic deactivation on thin TEM membranes. Electron diffraction (ED) enabled studying the structural and associated chemical changes as iron oxide reduces in the H2 environment. Finally, real-time TEM imaging also enabled monitoring the evolution of a population of nanoparticles during annealing. Results revealed the progressive restructuring and reduction of the as-deposited iron oxide film that occur during annealing in H2. As shown in Figs. 2(b)2(e), the ED patterns before annealing exhibited multiple continuous rings, indicating diffraction from multiple crystalline structures that represent a mixture of oxide phases. As temperature is raised during annealing up to 750 °C, distinct reflection points on the rings emerge, which signifies the restructuring of a polycrystalline film to form larger crystallites. Even with dwelling at 750 °C for more than 100 min, the oxide reduction is not complete, as can be inferred from the presence of a mixture of rings corresponding to metallic Fe and oxide phases [Fig. 2(e)].

FIG. 2

In situ characterization of catalyst film evolution during annealing by TEM and ED. (a) Schematic showing the growth of CNTs on TEM membranes inside an E-TEM. (b–e) ED patterns during heating the FexOy/AlxOy catalyst film in hydrogen, showing the reduction to metallic Fe with extended dwell time at 750 °C, as confirmed by the emergence of the red rings at interplanar spacings that are characteristic of metallic Fe (scale bar: 3 nm−1). (f, g) TEM images taken at different temperatures, showing film restructuring during annealing and particle formation by dewetting after 96 min at 750 °C (scale bar: 10 nm). Adapted with permission from Ref. 43. Copyright 2016 American Chemical Society.

Hence, annealing the thin film iron oxide up to 750 °C in H2 in vacuum (40 mTorr) does not fully reduce the catalyst to the metallic phase.42,44 Experimental studies have also shown that heating using a hot tungsten filament up to 2000 °C produces atomic hydrogen that rapidly reduces the catalyst.16,45 Other strong reducing agents such as ammonia (NH3)42 and hydrazine (N2H4)46 were also shown to cause the complete reduction of iron oxide. The reduction and phase change of Fe catalyst are therefore dependent on the annealing conditions, such as temperature, pressure, dwell time, and the gas environment.

As shown in Fig. 3, in situ GI-SAXS was used to study the dynamics of nanoparticle formation by dewetting (agglomeration), and the results showed that this process is rapid once a sufficiently high temperature is reached during fast heating. Mounting the reactor in the beamline of a synchrotron source also enabled GI-SAXS to uniquely track the time evolution of the statistical distribution of nanoparticle sizes and shapes.38 Although GI-SAXS is well-suited to studying dewetting, once CNTs start nucleating it becomes difficult to decouple the scattering coming from CNTs form that coming from the nanoparticles. Eventually, CNT scattering dominates, obscuring any information about the evolution of nanoparticles during growth. Importantly, using scattering intensity as an indication of CNT, both GI-SAXS and GI-XRD clearly demonstrate that the lift-off of aligned CNT forests from tangled CNT mats is an abrupt process.38,47

FIG. 3

Schematics and in situ GI-SAXS patterns of the successive stages of catalyst preparation and CNT nucleation: (a) As-deposited Fe/AlxOy film before heating; (b) Fe/AlxOy film being rapidly heated, showing the formation of nanoparticles by dewetting; (c) CNT nucleation from Fe catalyst nanoparticles; and (d) CNT growth, where scattering from CNTs from the transmitted X-ray beam dominate the collected 2D pattern, obscuring scattering from the nanoparticles. A schematic of scattering geometry corresponding to each pattern is shown above the pattern, and a plot of X-ray intensity (I) versus inverse space parameter (q) along the dashed line in the SAXS pattern is shown below each pattern. The blue shaded part of scattering is used for analysis. Reprinted with permission from Ref. 38. Copyright 2012 American Chemical Society.


Although, there are different schools of thought with respect to the exact atomic scale physicochemical processes underlying catalytic activation and nucleation of CNTs,48 the process generally proceeds by the arrangement of carbon atoms on the surface of the catalyst nanoparticles, leading to cap formation and liftoff. A major challenge is identifying which phase is the catalytically active phase and which pathways leads to the most active CNT growth (faster growth kinetics and higher density of CNTs). Toward this end, Hofmann et al. used in situ XPS to demonstrate that reducing Fe3+ and Fe2+ to the more catalytically active metallic Fe phase is required for efficient CNT nucleation.42 De los Arcos et al. also used the same characterization technique of in situ XPS, as shown in Fig. 4, to identify that active catalyst phase to be either Fe or FeO depending on properties of the buffer layer (chemical and morphological).39 An advantage of using XPS is that it enabled directly monitoring that the transition from chemisorbed carbon to graphitic carbon deposition by looking at the evolution of the core carbon 1s peak. This transition of binding energy, shown in Fig. 5, can be used as an indication of the formation and lift-off of nucleating CNTs.41 However, the penetration depth in XPS analysis is typically limited (∼2 nm), which prevents the continued characterization once CNTs cover the catalyst nanoparticles.

FIG. 4

In situ XPS results, showing the Fe 2p core lines at successive stages of catalyst preparation and CNT nucleation on different support layers (Al2O3, TiN and TiO2). (a) Measurement collected before annealing (as-deposited). (b) Measurement collected after annealing in a vacuum (10−5 mbar) up to 840 °C for 8 min. (c) Measurement collected after annealing the samples for 8 min followed by exposure to C2H2 for 5 s. Reprinted with permission from Ref. 39. Copyright 2004 American Chemical Society.

FIG. 5

In situ XPS of the C 1s core level during Fe exposure to C2H2 at 580 °C (∼2 × 10−7 mbar). Inset on the right show an SEM image of CNTs grown on the same part of the substrate. Inset on the left show the time-evolution of the chemisorbed (dots) and graphitic (crosses) carbon peaks. Adapted with permission from Ref. 41. Copyright 2007 American Chemical Society.

The catalytic activity and phase dynamics of Fe-based catalysts were also studied by in situ ED, and results showed that iron carbide is formed as a result of exposing body-centered cubic (BCC) metallic iron to C2H2. In that study, the cementite phase (Fe3C) was shown to be the active phase required for CNT growth, and the carbon-rich Hägg phase (Fe5C2) was shown to be the inactive (catalytically poisoned) phase.49 Additional in situ GI-XRD characterization also showed the dynamics of catalyst phase change, wherein if you start with FCC-rich iron catalyst (γ-Fe), the metallic Fe is the active phase without the need for carbide formation. On the other hand, if you start with a BCC-rich metallic phase (α-Fe), carbide formation is important for the growth process.50

Hence, individual catalyst nanoparticles within large populations typically follow a variety of different pathways during the successive stages of annealing and changes in the gas environment. These observations highlight the importance of any inherent variability in size, shape, and chemical composition among catalyst nanoparticles. Also, the spatial distribution of surface contaminants and any other local interactions can play a role in influencing the catalytic activity and the phase change dynamics.

At the scale of individual nanoparticles, in situ E-TEM imaging of CNT nucleation informed the understanding of the atomic scale mechanisms of graphitic cap formation and liftoff.41,5053 Hence, E-TEM enabled the direct measurement of CNT growth kinetics of individual CNTs growing from a single catalyst nanoparticle, as shown in Fig. 6.

FIG. 6

(a–d) In situ TEM images showing the growth of a single CNT with time. (e) Extracted growth kinetics for an individual CNT. Adapted with permission from Ref. 51. Copyright 2006 American Chemical Society.

More recently, E-TEM has been applied to observe the nucleation and growth of a large number of CNTs within the field of view, as shown in Fig. 7. In situ E-TEM imaging of catalyst populations, with more than 200 particles in the same image enabled plotting the population kinetics of catalyst nanoparticle formation by dewetting [Fig. 7(e)]. The accelerated dewetting behavior upon C2H2 exposure observed in this study was attributed to the reduction of iron oxide, leading to the sudden appearance, or “popping,” of the fully formed catalyst nanoparticle in view in the E-TEM image.43In situ TEM imaging also enabled studying the mechanical interactions between CNTs as they crowd each other and self-organize into the aligned structure [Figs. 7(f) and 7(g)].43,54

FIG. 7

(a–d) In situ E-TEM images showing the population dynamics of nanoparticle formation by dewetting as well as the nucleation of CNTs (Scale bar is 50 nm). (e) Time evolution of the number of nanoparticles and nucleating CNTs. (f, g) TEM images showing the mechanical interactions between CNTs and their self-organization during crowding (Scale bar is 50 nm). Adapted with permission from Ref. 43. Copyright 2016 American Chemical Society.

Importantly, different carbon-containing feedstock gases were used in CVD growth of CNTs, including acetylene,55 ethylene,56 methane,57 ethanol,58 and carbon monoxide.59 Moreover, other additives were explored to assist growth by either accelerating the growth rate or prolonging the catalyst life, such as water, oxygen, air, ethanol, carbon dioxide, acetone, tetrahydrofuran, methylbenzoate, and benzoaldehyde.4,6063 This review focuses on CVD growth of CNTs using acetylene and ethylene feedstock, and does not focus on the chemistry of growth enhancers.


Toward a mechanistic understanding of CNT growth and termination, characterization of the structure of a CNT forest is needed: from the macroscopic dimensions down to the atomic scale structure. In contrast to the previous category, which relied heavily on surface characterization techniques, the third category involves noncontact sensing of CNT forests and imaging their hierarchical morphology at multiple length-scales, shown in Fig. 8, along with spectroscopic and scattering-based techniques. For example, the evolution of forest morphology was heavily studied using ex situ SEM, to reveal the mechanism of growth temination.64,65

FIG. 8

Imaging a CNT forest at multiple length-scales. (a) Optical imaging of the macroscale forests (Adapted with permission from Ref. 7. Copyright 2011 American Chemical Society) (b) SEM imaging of the microstructure (Adapted with permission from Ref. 7. Copyright 2011 American Chemical Society). (c) Schematic of the nanoscale and mesoscale morphology of the tangled array of tortuous CNTs. (d) SEM showing the hierarchical forest morphology of bundled and tortuous CNTs (Adapted with permission from Ref. 7. Copyright 2011 American Chemical Society). (e) Schematic showing the concentric walls of a multi-wall CNT. (f) TEM image showing the walls of a CNT (Adapted with permission from Ref. 7. Copyright 2011 American Chemical Society). (g) Schematic showing the atomic structure of graphitic carbon walls with a Stone–Wales defect (Adapted with permission from Ref. 66. Copyright 2000 Elsevier). (h) STM image of CNT wall with Stone-Wales defect (Adapted with permission from Ref. 66. Copyright 2000 Elsevier).

A large number of in situ and ex situ techniques were previously explored for the nondestructive characterization of CNT growth kinetics. For example, optical photography and videography,67,68 optical interference,69 single-slit laser diffractography,70 time-resolved reflectivity,9 laser triangulation,71,72 and cycling of growth to create stacked structures visible by SEM.64,73,74 Importantly, all of the abovementioned methods only enables quantifying the height kinetics. On the other hand, real-time mass measurements are more challenging, and have been achieved in the past generally by using a microbalance either ex situ,5,75 or in situ.76 Weighing samples, however, imposes limitations on the resolution of the measurement and does not enable spatial mapping of mass and density across an individual forest.

Indirect measurements of density were obtained from ex situ Z-contrast transmission electron microscopy (Z-STEM) imaging, as well as from real-time changes in the effective extinction coefficient in time-resolved optical reflectivity (TRR).7779 Also, in situ Raman spectroscopy can be used to provide a measure of relative mass kinetics from real-time integration of the area under the G-band.8083 Real-time monitoring of the G-band during growth of single-wall CNTs was instrumental in demonstrating that the growth rate is dependent on CNT chirality.84 Recently, in situ electron energy loss spectroscopy (EELS) was used to quantify the accumulating carbon on the surface during CNT growth inside E-TEM, by plotting the time evolution of the carbon K-edge near-edge structure.43 While some of these indirect approaches can be utilized for spatial mapping of density, they can only infer relative density.

As shown in Fig. 9, X-ray attenuation has been shown to enable accurate spatial mapping of absolute mass density of CNT forests down to a spatial resolution of 10 µm (limited by the size of the focused/trimmed synchrotron X-ray beam). A major advantage of this approach is that information about the evolution of diameter distribution and alignment are obtained simultaneously by analyzing SAXS patterns, as shown in Fig. 10.57,72,85 In fact, Hermans orientation parameter can be used to measure the degree of alignment by quantifying the anisotropy in scattering patterns, obtained by either small angle neutron scattering (SANS)86 or SAXS.5,72,85 Combining high resolution spatial mapping of X-ray scattering and intensity attenuation measurements,5,7 with real-time height kinetics of CNT growth obtained by noncontact laser triangulation,71,72 enabled revealing the spatiotemporal evolution of mass density, number density, and cumulative CNT areal density with unprecedented accuracy throughout the stages of CNT growth [Fig. 9(b)].

FIG. 9

(a) Schematic of the experimental set-up, wherein a CNT forest is placed on a motorized stage in a synchrotron beamline, and the beam is focused to a 10 µm spot. (b) Time evolution of mass density and number of density of CNTs, fitted to a Gompertz model of population growth. Adapted with permission from Ref. 7. Copyright 2011 American Chemical Society.

FIG. 10

(a) Spatial mapping of the Hermans orientation parameter by processing SAXS patterns for forests grown in a hot wall reactor for different growth times. Adapted with permission from Ref. 5. Copyright 2009 American Chemical Society. (b) Probability density function of CNT diameter distribution in the topmost and bottommost slices of a CNT forest. Adapted with permission from Ref. 8. Copyright 2012 Elsevier. (c) Diameter dependent growth kinetics obtained by combing diameter distributions with forest mass kinetics. Adapted with permission from Ref. 8. Copyright 2012 Elsevier.

As a result, CNT forest growth is explained as a time-varying population of individual CNTs that have a variation of growth rates, while interacting together within a growing forest. This collective growth picture emerged in contrast to studies that explain CNT forest growth behavior based on mathematical modeling of the behavior of a single catalyst nanoparticle-CNT system.9,36,87,88 As shown in Fig. 9(b), the mass kinetics exhibit an S-shaped curve, which is fitted by the Gompertz model of population growth. This phenomenological fit indicated that the CNT population dynamics exhibit an autocatalytic nature. Combing this result with the evolution of diameter distributions during CNT growth [Fig. 10(b)] reveals the diameter dependent population growth dynamics [Fig. 10(c)]. Hence, small angle X-ray scattering (SAXS)85,89 and ultra-small angle X-ray scattering (USAXS)90 provide accurate information about density, diameters, bundle size, and alignment of CNTs in a growing forest.

Taken together, these results help paint a picture of the collective growth mechanism of CNT forests, as shown schematically in Fig. 1, starting with the nucleation of randomly oriented CNTs that interact with each other as their density increases. This crowding leads to the build-up of a self-supporting aligned morphology when the density reaches a threshold that was previously identified by numerical and experimental analysis to be in the order of 109 CNTs/cm2.5,7 The CNT forest then grows steadily until density starts to decay as a result of the deactivation of individual CNTs in the growing population. This density decay proceeds until the density becomes too low to support the vertically aligned forest structure (lower than the abovementioned threshold density), at which point growth self-termination is observed. At the point of termination, forest height stops increasing, which is characterized by significant loss of alignment at the bottom of the forest.5,7

It is also probable that some CNTs continue to grow beyond the apparent cessation of forest height kinetics, but their number is too small to push the forest upward. This post-termination evolution likely leads to the accumulation of more tortuous CNTs at the interface between the forest and substrate, and may help control the adhesion of the as-grown CNT forest to the substrate on which it is grown. Hence, employing different cooling recipes, along with using H2O etching can tune forest–substrate interactions.91


Based on the current understanding of CNT growth dynamics, there have been significant advances toward controlling CNT growth by CVD, such as efforts toward improving the control on CNT diameters, chirality, and/or density.37,61,9295 In the future, more improvements are expected in the area of catalyst design and process engineering toward more deterministic control on the overall CNT quality (straightness and defect density) and precise atomic structure, including both mono-chiral and monodisperse diameter distribution of as-grown CNTs. In addition, more understanding on what factors determine whether a catalyst nanoparticle becomes active or inactive in a large population is likely to come by combining multiple in situ characterization techniques, such as combining TEM, ED, and EELS inside the E-TEM.43 Understanding the spatial distribution of catalytic activity on substrates that arise from chemical coupling effects,96 or from designed catalyst gradients/steps,60,97 also enables engineering the three-dimensional geometry of microscale/macroscale CNT structures.

Another challenge that still plagues CNT growth is the deactivation of growth or self-termination, which was previously heavily studied, leading to proposing multiple mechanisms that are likely to be competing, such as catalyst poisoning, overcoating, evaporation or diffusion, nanoparticle coarsening and CNT mechanical coupling.9,16,18,36,98100 Studying the mechanochemical aspects of CNT growth, wherein the effects of mechanical forces on the catalytic process are analyzed both experimentally and numerically, is an area of current research and will enable better understating and control on the CNT growth process. A deeper understanding of all the competing deactivation mechanisms and identifying the dominant ones will open the door for approaches to overcome them. This is still required for the fabrication of ultra-long CNTs for application such as structural fibers and transmission lines.

Finally, from a practical perspective, the realization of many applications requires scaling the fabrication process, such as by roll-to-roll processing,101 along with exercising more control on the inherent process variabilities that could compromise the properties of produced CNTs. Integrating aligned CNT films into functional devices invites the need to grow CNTs directly on different types of substrates such as metallic foils for instance.22,102 Moreover, some applications require weak adhesion with substrate, such as in cases of transfer.103 Other applications require strong adhesion, such as using CNTs as adhesives,104 and rolling CNTs to form horizontally aligned structures.91,105 Hence, controlling the post-termination evolution, shown in Fig. 1, could be an important complement to controlling CNT growth, to tune the mechanical adhesion, as well as the electrical and thermal resistance at the CNT-substrate interface.


This article presented a nonexhaustive overview of different characterization techniques that were utilized to study the successive stages of collective CNT forest growth, with particular focus on methods that are based on synchrotron X-ray scattering and mass attenuation, environmental transmission electron microscopy (E-TEM), electron diffraction (ED), and other spectroscopic techniques. In situ techniques were classified into three categories depending on the stage of the growth process. As shown schematically in Fig. 1, in the first category of catalyst preparation and treatment, thin film restructuring and nanoparticle formation by dewetting are characterized by surface characterization techniques during annealing. The second category of studying catalytic activation and CNT nucleation included efforts toward understanding the atomic pathways leading to the arrangement of carbon atoms on the catalyst and the lift-off of CNTs that interact with other CNTs in proximity. Finally, the third category summarized research on monitoring CNT growth and termination, with emphasis on methodologies for understanding the mechanochemical kinetics and mechanisms of catalytic deactivation. Combining all three categories together provides insights into building the process–structure relationship, which is at the heart of the science and technology of CNT fabrication. Hence, these efforts open the door for producing designed CNT structures having predictable morphology and tailored properties for specific applications.


  1. 1.

    R.H. Baughman, A.A. Zakhidov, and W.A. de Heer: Carbon nanotubes—The route toward applications. Science 297(5582), 787 (2002).

    CAS  Google Scholar 

  2. 2.

    M.F.L. De Volder, S.H. Tawfick, R.H. Baughman, and A.J. Hart: Carbon nanotubes: present and future commercial applications. Science 339(6119), 535 (2013).

    Google Scholar 

  3. 3.

    A.M. Cassell, J.A. Raymakers, J. Kong, and H. Dai: Large scale CVD synthesis of single-walled carbon nanotubes. J. Phys. Chem. B 103(31), 6484 (1999).

    CAS  Google Scholar 

  4. 4.

    K. Hata, D.N. Futaba, K. Mizuno, T. Namai, M. Yumura, and S. Iijima: Water-assisted highly efficient synthesis of impurity-free single-walled carbon nanotubes. Science 306(5700), 1362 (2004).

    CAS  Google Scholar 

  5. 5.

    M. Bedewy, E.R. Meshot, H. Guo, E.A. Verploegen, W. Lu, and A.J. Hart: Collective mechanism for the evolution and self-termination of vertically aligned carbon nanotube growth. J. Phys. Chem. C 113(48), 20576 (2009).

    CAS  Google Scholar 

  6. 6.

    E. Meshot, M. Bedewy, K. Lyons, A. Woll, K. Juggernauth, S. Tawfick, and A. Hart: Measuring the lengthening kinetics of aligned nanostructures by spatiotemporal correlation of height and orientation. Nanoscale 2(6), 896 (2010).

    Google Scholar 

  7. 7.

    M. Bedewy, E.R. Meshot, M.J. Reinker, and A.J. Hart: Population growth dynamics of carbon nanotubes. ACS Nano 5(11), 8974 (2011).

    CAS  Google Scholar 

  8. 8.

    M. Bedewy, E.R. Meshot, and A.J. Hart: Diameter-dependent kinetics of activation and deactivation in carbon nanotube population growth. Carbon 50(14), 5106 (2012).

    CAS  Google Scholar 

  9. 9.

    A.A. Puretzky, D.B. Geohegan, S. Jesse, I.N. Ivanov, and G. Eres: In situ measurements and modeling of carbon nanotube array growth kinetics during chemical vapor deposition. Appl. Phys. A: Mater. Sci. Process. 81(2), 223 (2005).

    CAS  Google Scholar 

  10. 10.

    D.N. Futaba, K. Hata, T. Namai, T. Yamada, K. Mizuno, Y. Hayamizu, M. Yumura, and S. Iijima: 84% catalyst activity of water-assisted growth of single walled carbon nanotube forest characterization by a statistical and macroscopic approach. J. Phys. Chem. B 110(15), 8035 (2006).

    CAS  Google Scholar 

  11. 11.

    S. Noda, K. Hasegawa, H. Sugime, K. Kakehi, Z. Zhang, S. Maruyama, and Y. Yukio: Millimeter-thick single-walled carbon nanotube forests: Hidden role of catalyst support. Jpn. J. Appl. Phys. 46(5L), L399 (2007).

    CAS  Google Scholar 

  12. 12.

    E. Einarsson, Y. Murakami, M. Kadowaki, and S. Maruyama: Growth dynamics of vertically aligned single-walled carbon nanotubes from in situ measurements. Carbon 46(6), 923 (2008).

    CAS  Google Scholar 

  13. 13.

    C.T. Wirth, C. Zhang, G. Zhong, S. Hofmann, and J. Robertson: Diffusion- and reaction-limited growth of carbon nanotube forests. ACS Nano 3(11), 3560 (2009).

    CAS  Google Scholar 

  14. 14.

    P. Vinten, J. Lefebvre, and P. Finnie: Kinetic critical temperature and optimized chemical vapor deposition growth of carbon nanotubes. Chem. Phys. Lett. 469(4–6), 293 (2009).

    CAS  Google Scholar 

  15. 15.

    P.B. Amama, C.L. Pint, S.M. Kim, L. McJilton, K.G. Eyink, E.A. Stach, R.H. Hauge, and B. Maruyama: Influence of alumina type on the evolution and activity of alumina-supported Fe catalysts in single-walled carbon nanotube carpet growth. ACS Nano 4(2), 895 (2010).

    CAS  Google Scholar 

  16. 16.

    P.B. Amama, C.L. Pint, L. McJilton, S.M. Kim, E.A. Stach, P.T. Murray, R.H. Hauge, and B. Maruyama: Role of water in super growth of single-walled carbon nanotube carpets. Nano Lett. 9(1), 44 (2009).

    CAS  Google Scholar 

  17. 17.

    S. Pathak, N. Mohan, E. Decolvenaere, A. Needleman, M. Bedewy, A.J. Hart, and J.R. Greer: Local relative density modulates failure and strength in vertically aligned carbon nanotubes. ACS Nano 7(10), 8593 (2013).

    CAS  Google Scholar 

  18. 18.

    M. Bedewy and A.J. Hart: Mechanical coupling limits the density and quality of self-organized carbon nanotube growth. Nanoscale 5(7), 2928 (2013).

    CAS  Google Scholar 

  19. 19.

    C.V. Thompson: Solid-state dewetting of thin films. Annu. Rev. Mater. Res. 42, 399 (2012).

    CAS  Google Scholar 

  20. 20.

    K.B.K. Teo, M. Chhowalla, G.A.J. Amaratunga, W.I. Milne, D.G. Hasko, G. Pirio, P. Legagneux, F. Wyczisk, and D. Pribat: Uniform patterned growth of carbon nanotubes without surface carbon. Appl. Phys. Lett. 79(10), 1534 (2001).

    CAS  Google Scholar 

  21. 21.

    Y. Li, J. Liu, Y. Wang, and Z.L. Wang: Preparation of monodispersed Fe−Mo nanoparticles as the catalyst for CVD synthesis of carbon nanotubes. Chem. Mater. 13(3), 1008 (2001).

    CAS  Google Scholar 

  22. 22.

    E.S. Polsen, M. Bedewy, and A.J. Hart: Decoupled control of carbon nanotube forest density and diameter by continuous-feed convective assembly of catalyst particles. Small 9(15), 2564 (2013).

    CAS  Google Scholar 

  23. 23.

    C. Hinderling, Y. Keles, T. Stöckli, H.F. Knapp, T. de los Arcos, P. Oelhafen, I. Korczagin, M.A. Hempenius, G.J. Vancso, R. Pugin, and H. Heinzelmann: Organometallic block copolymers as catalyst precursors for templated carbon nanotube growth. Adv. Mater. 16(11), 876 (2004).

    CAS  Google Scholar 

  24. 24.

    R.T.K. Baker, M.A. Barber, P.S. Harris, F.S. Feates, and R.J. Waite: Nucleation and growth of carbon deposits from the nickel catalyzed decomposition of acetylene. J. Catal. 26(1), 51 (1972).

    CAS  Google Scholar 

  25. 25.

    A.R. Harutyunyan, O.A. Kuznetsov, C.J. Brooks, E. Mora, and G. Chen: Thermodynamics behind carbon nanotube growth via endothermic catalytic decomposition reaction. ACS Nano 3(2), 379 (2009).

    CAS  Google Scholar 

  26. 26.

    S.M. Bachilo, L. Balzano, J.E. Herrera, F. Pompeo, D.E. Resasco, and R.B. Weisman: Narrow (n,m)-distribution of single-walled carbon nanotubes grown using a solid supported catalyst. J. Am. Chem. Soc. 125(37), 11186 (2003).

    CAS  Google Scholar 

  27. 27.

    T. de los Arcos, M. Gunnar Garnier, P. Oelhafen, D. Mathys, J. Won Seo, C. Domingo, J. Vicente García-Ramos, and S. Sánchez-Cortés: Strong influence of buffer layer type on carbon nanotube characteristics. Carbon 42(1), 187 (2004).

    Google Scholar 

  28. 28.

    W-H. Chiang and R.M. Sankaran: Synergistic effects in bimetallic nanoparticles for low temperature carbon nanotube growth. Adv. Mater. 20(24), 4857 (2008).

    CAS  Google Scholar 

  29. 29.

    B. Kitiyanan, W.E. Alvarez, J.H. Harwell, and D.E. Resasco: Controlled production of single-wall carbon nanotubes by catalytic decomposition of CO on bimetallic Co–Mo catalysts. Chem. Phys. Lett. 317(3–5), 497 (2000).

    CAS  Google Scholar 

  30. 30.

    S. Wang, A.Y. Borisevich, S.N. Rashkeev, M.V. Glazoff, K. Sohlberg, S.J. Pennycook, and S.T. Pantelides: Dopants adsorbed as single atoms prevent degradation of catalysts. Nat. Mater. 3(3), 143 (2004).

    CAS  Google Scholar 

  31. 31.

    V. Shanov, A. Gorton, Y.H. Yun, and M. Schulz: Composite catalyst and method for manufacturing carbon nanostructured materials, US Patent Application 2008/095695.

  32. 32.

    A.E. Islam, P. Nikolaev, P.B. Amama, S. Saber, D. Zakharov, D. Huffman, M. Erford, G. Sargent, S.L. Semiatin, E.A. Stach, and B. Maruyama: Engineering the activity and lifetime of heterogeneous catalysts for carbon nanotube growth via substrate ion beam bombardment. Nano Lett. 14(9), 4997 (2014).

    CAS  Google Scholar 

  33. 33.

    H. Dai, A.G. Rinzler, P. Nikolaev, A. Thess, D.T. Colbert, and R.E. Smalley: Single-wall nanotubes produced by metal-catalyzed disproportionation of carbon monoxide. Chem. Phys. Lett. 260(3), 471 (1996).

    CAS  Google Scholar 

  34. 34.

    I. Sushumna and E. Ruckenstein: Role of physical and chemical interactions in the behavior of supported metal-catalysts—iron on alumina—A case-study. J. Catal. 94(1), 239 (1985).

    CAS  Google Scholar 

  35. 35.

    A. Gohier, C.P. Ewels, T.M. Minea, and M.A. Djouadi: Carbon nanotube growth mechanism switches from tip- to base-growth with decreasing catalyst particle size. Carbon 46(10), 1331 (2008).

    CAS  Google Scholar 

  36. 36.

    M. Stadermann, S.P. Sherlock, J-B. In, F. Fornasiero, H.G. Park, A.B. Artyukhin, Y. Wang, J.J. De Yoreo, C.P. Grigoropoulos, O. Bakajin, A.A. Chernov, and A. Noy: Mechanism and kinetics of growth termination in controlled chemical vapor deposition growth of multiwall carbon nanotube arrays. Nano Lett. 9(2), 738 (2009).

    CAS  Google Scholar 

  37. 37.

    K. Hasegawa and S. Noda: Diameter increase in millimeter-tall vertically aligned single-walled carbon nanotubes during growth. Appl. Phys. Express 3(4), 045103 (2010).

    Google Scholar 

  38. 38.

    E.R. Meshot, E. Verploegen, M. Bedewy, S. Tawfick, A.R. Woll, K.S. Green, M. Hromalik, L.J. Koerner, H.T. Philipp, M.W. Tate, S.M. Gruner, and A.J. Hart: High-speed in situ X-ray scattering of carbon nanotube film nucleation and self-organization. ACS Nano 6(6), 5091 (2012).

    CAS  Google Scholar 

  39. 39.

    T. de los Arcos, M.G. Garnier, J.W. Seo, P. Oelhafen, V. Thommen, and D. Mathys: The influence of catalyst chemical state and morphology on carbon nanotube growth. J. Phys. Chem. B 108(23), 7728 (2004).

    Google Scholar 

  40. 40.

    C. Mattevi, C.T. Wirth, S. Hofmann, R. Blume, M. Cantoro, C. Ducati, C. Cepek, A. Knop-Gericke, S. Milne, C. Castellarin-Cudia, S. Dolafi, A. Goldoni, R. Schloegl, and J. Robertson: In-situ X-ray photoelectron spectroscopy study of catalyst−support interactions and growth of carbon nanotube forests. J. Phys. Chem. C 112(32), 12207 (2008).

    CAS  Google Scholar 

  41. 41.

    S. Hofmann, R. Sharma, C. Ducati, G. Du, C. Mattevi, C. Cepek, M. Cantoro, S. Pisana, A. Parvez, F. Cervantes-Sodi, A.C. Ferrari, R. Dunin-Borkowski, S. Lizzit, L. Petaccia, A. Goldoni, and J. Robertson: In situ observations of catalyst dynamics during surface-bound carbon nanotube nucleation. Nano Lett. 7(3), 602 (2007).

    CAS  Google Scholar 

  42. 42.

    S. Hofmann, R. Blume, C.T. Wirth, M. Cantoro, R. Sharma, C. Ducati, M. Hävecker, S. Zafeiratos, P. Schnoerch, A. Oestereich, D. Teschner, M. Albrecht, A. Knop-Gericke, R. Schlögl, and J. Robertson: State of transition metal catalysts during carbon nanotube growth. J. Phys. Chem. C 113(5), 1648 (2009).

    CAS  Google Scholar 

  43. 43.

    M. Bedewy, B. Viswanath, E.R. Meshot, D.N. Zakharov, E.A. Stach, and A.J. Hart: Measurement of the dewetting, nucleation, and deactivation kinetics of carbon nanotube population growth by environmental transmission electron microscopy. Chem. Mater. 28(11), 3804 (2016).

    CAS  Google Scholar 

  44. 44.

    R. Sharma, E. Moore, P. Rez, and M.M.J. Treacy: Site-specific fabrication of Fe particles for carbon nanotube growth. Nano Lett. 9(2), 689 (2009).

    CAS  Google Scholar 

  45. 45.

    Y-Q. Xu, E. Flor, H. Schmidt, R.E. Smalley, and R.H. Hauge: Effects of atomic hydrogen and active carbon species in 1 mm vertically aligned single-walled carbon nanotube growth. Appl. Phys. Lett. 89(12), 123116 (2006).

    Google Scholar 

  46. 46.

    C.L. Pint, S.M. Kim, E.A. Stach, and R.H. Hauge: Rapid and scalable reduction of dense surface-supported metal-oxide catalyst with hydrazine vapor. ACS Nano 3(7), 1897 (2009).

    CAS  Google Scholar 

  47. 47.

    P. Landois, M. Pinault, S. Rouzière, D. Porterat, C. Mocuta, E. Elkaim, M. Mayne-L’Hermite, and P. Launois: In situ time resolved wide angle X-ray diffraction study of nanotube carpet growth: Nature of catalyst particles and progressive nanotube alignment. Carbon 87, 246 (2015).

    CAS  Google Scholar 

  48. 48.

    J-P. Tessonnier and D.S. Su: Recent progress on the growth mechanism of carbon nanotubes: A review. ChemSusChem 4(7), 824 (2011).

    CAS  Google Scholar 

  49. 49.

    S. Mazzucco, Y. Wang, M. Tanase, M. Picher, K. Li, Z. Wu, S. Irle, and R. Sharma: Direct evidence of active and inactive phases of Fe catalyst nanoparticles for carbon nanotube formation. J. Catal. 319, 54 (2014).

    CAS  Google Scholar 

  50. 50.

    C.T. Wirth, B.C. Bayer, A.D. Gamalski, S. Esconjauregui, R.S. Weatherup, C. Ducati, C. Baehtz, J. Robertson, and S. Hofmann: The phase of iron catalyst nanoparticles during carbon nanotube growth. Chem. Mater. 24(24), 4633 (2012).

    CAS  Google Scholar 

  51. 51.

    M. Lin, J.P.Y. Tan, C. Boothroyd, K.P. Loh, E.S. Tok, and Y.L. Foo: Direct observation of single-walled carbon nanotube growth at the atomistic scale. Nano Lett. 6(3), 449 (2006).

    CAS  Google Scholar 

  52. 52.

    H. Yoshida, S. Takeda, T. Uchiyama, H. Kohno, and Y. Homma: Atomic-scale in situ observation of carbon nanotube growth from solid state iron carbide nanoparticles. Nano Lett. 8(7), 2082 (2008).

    CAS  Google Scholar 

  53. 53.

    M. Moseler, F. Cervantes-Sodi, S. Hofmann, G. Csanyi, and A.C. Ferrari: Dynamic catalyst restructuring during carbon nanotube growth. ACS Nano 4(12), 7587 (2010).

    CAS  Google Scholar 

  54. 54.

    V. Balakrishnan, M. Bedewy, E.R. Meshot, S.W. Pattinson, E.S. Polsen, F. Laye, D.N. Zakharov, E.A. Stach, and A.J. Hart: Real time imaging of self-organization and mechanical competition in carbon nanotube forest growth. ACS Nano (2017). Accepted.

  55. 55.

    Z.P. Huang, J.W. Xu, Z.F. Ren, J.H. Wang, M.P. Siegal, and P.N. Provencio: Growth of highly oriented carbon nanotubes by plasma-enhanced hot filament chemical vapor deposition. Appl. Phys. Lett. 73(26), 3845 (1998).

    CAS  Google Scholar 

  56. 56.

    S. Fan, M.G. Chapline, N.R. Franklin, T.W. Tombler, A.M. Cassell, and H. Dai: Self-oriented regular arrays of carbon nanotubes and their field emission properties. Science 283(5401), 512 (1999).

    CAS  Google Scholar 

  57. 57.

    J. Kong, A.M. Cassell, and H. Dai: Chemical vapor deposition of methane for single-walled carbon nanotubes. Chem. Phys. Lett. 292(4–6), 567 (1998).

    CAS  Google Scholar 

  58. 58.

    S. Maruyama, E. Einarsson, Y. Murakami, and T. Edamura: Growth process of vertically aligned single-walled carbon nanotubes. Chem. Phys. Lett. 403(4–6), 320 (2005).

    CAS  Google Scholar 

  59. 59.

    B. Zheng, C. Lu, G. Gu, A. Makarovski, G. Finkelstein, and J. Liu: Efficient CVD growth of single-walled carbon nanotubes on surfaces using carbon monoxide precursor. Nano Lett. 2(8), 895 (2002).

    CAS  Google Scholar 

  60. 60.

    Y. Zhang, J.M. Gregoire, R.B. van Dover, and A.J. Hart: Ethanol-promoted high-yield growth of few-walled carbon nanotubes. J. Phys. Chem. C 114(14), 6389 (2010).

    CAS  Google Scholar 

  61. 61.

    D.N. Futaba, J. Goto, S. Yasuda, T. Yamada, M. Yumura, and K. Hata: General rules governing the highly efficient growth of carbon nanotubes. Adv. Mater. 21(47), 4811 (2009).

    CAS  Google Scholar 

  62. 62.

    C.L. Pint, S.T. Pheasant, A.N.G. Parra-Vasquez, C. Horton, Y. Xu, and R.H. Hauge: Investigation of optimal parameters for oxide-assisted growth of vertically aligned single-walled carbon nanotubes. J. Phys. Chem. C 113(10), 4125 (2009).

    CAS  Google Scholar 

  63. 63.

    X. Li, X. Zhang, L. Ci, R. Shah, C. Wolfe, S. Kar, S. Talapatra, and P. Ajayan: Air-assisted growth of ultra-long carbon nanotube bundles. Nanotechnology 19(45), 455609 (2008).

    Google Scholar 

  64. 64.

    L. Zhu, D.W. Hess, and C-P. Wong: Monitoring carbon nanotube growth by formation of nanotube stacks and investigation of the diffusion-controlled kinetics. J. Phys. Chem. B 110(11), 5445 (2006).

    CAS  Google Scholar 

  65. 65.

    P. Vinten, P. Marshall, J. Lefebvre, and P. Finnie: Distinct termination morphologies for vertically aligned carbon nanotube forests. Nanotechnology 21(3), 035603 (2010).

    CAS  Google Scholar 

  66. 66.

    V. Meunier and P. Lambin: Scanning tunneling microscopy and spectroscopy of topological defects in carbon nanotubes. Carbon 38(11–12), 1729 (2000).

    CAS  Google Scholar 

  67. 67.

    A.J. Hart, L. van Laake, and A.H. Slocum: Desktop growth of carbon-nanotube monoliths with in situ optical imaging. Small 3(5), 772 (2007).

    CAS  Google Scholar 

  68. 68.

    A.A. Puretzky, G. Eres, C.M. Rouleau, I.N. Ivanov, and D.B. Geohegan: Real-time imaging of vertically aligned carbon nanotube array growth kinetics. Nanotechnology 19(5), 055605 (2008).

    CAS  Google Scholar 

  69. 69.

    D-H. Kim, H-S. Jang, C-D. Kim, D-S. Cho, H-S. Yang, H-D. Kang, B-K. Min, and H-R. Lee: Dynamic growth rate behavior of a carbon nanotube forest characterized by in situ optical growth monitoring. Nano Lett. 3(6), 863 (2003).

    CAS  Google Scholar 

  70. 70.

    L.M. Dell’Acqua-Bellavitis, J.D. Ballard, P.M. Ajayan, and R.W. Siegel: Kinetics for the synthesis reaction of aligned carbon nanotubes: A study based on in situ diffractography. Nano Lett. 4(9), 1613 (2004).

    Google Scholar 

  71. 71.

    E.R. Meshot and A.J. Hart: Abrupt self-termination of vertically aligned carbon nanotube growth. Appl. Phys. Lett. 92(11), 113107 (2008).

    Google Scholar 

  72. 72.

    E.R. Meshot, D.L. Plata, S. Tawfick, Y. Zhang, E.A. Verploegen, and A.J. Hart: Engineering vertically aligned carbon nanotube growth by decoupled thermal treatment of precursor and catalyst. ACS Nano 3(9), 2477 (2009).

    CAS  Google Scholar 

  73. 73.

    T. Iwasaki, G.F. Zhong, T. Aikawa, T. Yoshida, and H. Kawarada: Direct evidence for root growth of vertically aligned single-walled carbon nanotubes by microwave plasma chemical vapor deposition. J. Phys. Chem. B 109(42), 19556 (2005).

    CAS  Google Scholar 

  74. 74.

    S.P. Patole, J.H. Park, T.Y. Lee, J.H. Lee, A.S. Patole, and J.B. Yoo: Growth interruption studies on vertically aligned 2–3 wall carbon nanotubes by water assisted chemical vapor deposition. Appl. Phys. Lett. 93(11), 114101 (2008).

    Google Scholar 

  75. 75.

    S. Yasuda, T. Hiraoka, D.N. Futaba, T. Yamada, M. Yumura, and K. Hata: Existence and kinetics of graphitic carbonaceous impurities in carbon nanotube forests to assess the absolute purity. Nano Lett. 9(2), 769 (2009).

    CAS  Google Scholar 

  76. 76.

    A.M. Valiente, P.N. Lopez, I.R. Ramos, A.G. Ruiz, C. Li, and Q. Xin: In situ study of carbon nanotube formation by C2H2 decomposition on an iron-based catalyst. Carbon 38(14), 2003 (2000).

    Google Scholar 

  77. 77.

    J.J. Jackson, A.A. Puretzky, K.L. More, C.M. Rouleau, G. Eres, and D.B. Geohegan: Pulsed growth of vertically aligned nanotube arrays with variable density. ACS Nano 4(12), 7573 (2010).

    CAS  Google Scholar 

  78. 78.

    D.B. Geohegan, A.A. Puretzky, J.J. Jackson, C.M. Rouleau, G. Eres, and K.L. More: Flux-dependent growth kinetics and diameter selectivity in single-wall carbon nanotube arrays. ACS Nano 5(10), 8311 (2011).

    CAS  Google Scholar 

  79. 79.

    A.A. Puretzky, D.B. Geohegan, J.J. Jackson, S. Pannala, G. Eres, C.M. Rouleau, K.L. More, N. Thonnard, and J.D. Readle: Incremental growth of short SWNT arrays by pulsed chemical vapor deposition. Small 8(10), 1534 (2012).

    CAS  Google Scholar 

  80. 80.

    M. Picher, E. Anglaret, R. Arenal, and V. Jourdain: Self-deactivation of single-walled carbon nanotube growth studied by in situ Raman measurements. Nano Lett. 9(2), 542 (2009).

    CAS  Google Scholar 

  81. 81.

    S. Chiashi, M. Kohno, Y. Takata, and S. Maruyama: Localized synthesis of single-walled carbon nanotubes on silicon substrates by a laser heating catalytic CVD. J. Phys. Conf. Ser. 59, 155–158 (2007).

    CAS  Google Scholar 

  82. 82.

    A. Li-Pook-Than, J. Lefebvre, and P. Finnie: Phases of carbon nanotube growth and population evolution from in situ Raman spectroscopy during chemical vapor deposition. J. Phys. Chem. C 114(25), 11018 (2010).

    CAS  Google Scholar 

  83. 83.

    N. Latorre, E. Romeo, F. Cazana, T. Ubieto, C. Royo, J.J. Villacampa, and A. Monzon: Carbon nanotube growth by catalytic chemical vapor deposition: A phenomenological kinetic model. J. Phys. Chem. C 114(11), 4773 (2010).

    CAS  Google Scholar 

  84. 84.

    R. Rao, D. Liptak, T. Cherukuri, B.I. Yakobson, and B. Maruyama: In situ evidence for chirality-dependent growth rates of individual carbon nanotubes. Nat. Mater. 11(3), 213 (2012).

    CAS  Google Scholar 

  85. 85.

    B.N. Wang, R.D. Bennett, E. Verploegen, A.J. Hart, and R.E. Cohen: Quantitative characterization of the morphology of multiwall carbon nanotube films by small-angle X-ray scattering. J. Phys. Chem. C 111(16), 5859 (2007).

    CAS  Google Scholar 

  86. 86.

    H. Wang, Z. Xu, and G. Eres: Order in vertically aligned carbon nanotube arrays. Appl. Phys. Lett. 88(21), 213111 (2006).

    Google Scholar 

  87. 87.

    O.A. Louchev, T. Laude, Y. Sato, and H. Kanda: Diffusion-controlled kinetics of carbon nanotube forest growth by chemical vapor deposition. J. Chem. Phys. 118(16), 7622 (2003).

    CAS  Google Scholar 

  88. 88.

    R.F. Wood, S. Pannala, J.C. Wells, A.A. Puretzky, and D.B. Geohegan: Simple model of the interrelation between single- and multiwall carbon nanotube growth rates for the CVD process. Phys. Rev. B: Condens. Matter Mater. Phys. 75(23), 235446 (2007).

    Google Scholar 

  89. 89.

    B.N. Wang, R.D. Bennett, E. Verploegen, A.J. Hart, and R.E. Cohen: Characterizing the morphologies of mechanically manipulated multiwall carbon nanotube films by small-angle X-ray scattering. J. Phys. Chem. C 111(48), 17933 (2007).

    CAS  Google Scholar 

  90. 90.

    E. Verploegen, A.J. Hart, M. De Volder, S. Tawfick, K-K. Chia, and R.E. Cohen: Non-destructive characterization of structural hierarchy within aligned carbon nanotube assemblies. J. Appl. Phys. 109(9), 094316 (2011).

    Google Scholar 

  91. 91.

    C.L. Pint, Y-Q. Xu, M. Pasquali, and R.H. Hauge: Formation of highly dense aligned ribbons and transparent films of single-walled carbon nanotubes directly from carpets. ACS Nano 2(9), 1871 (2008).

    CAS  Google Scholar 

  92. 92.

    G. Zhong, J.H. Warner, M. Fouquet, A.W. Robertson, B. Chen, and J. Robertson: Growth of ultrahigh density single-walled carbon nanotube forests by improved catalyst design. ACS Nano 6(4), 2893 (2012).

    CAS  Google Scholar 

  93. 93.

    S.K. Youn, N. Yazdani, J. Patscheider, and H.G. Park: Facile diameter control of vertically aligned, narrow single-walled carbon nanotubes. RSC Adv. 3(5), 1434 (2013).

    CAS  Google Scholar 

  94. 94.

    J.R. Sanchez-Valencia, T. Dienel, O. Groning, I. Shorubalko, A. Mueller, M. Jansen, K. Amsharov, P. Ruffieux, and R. Fasel: Controlled synthesis of single-chirality carbon nanotubes. Nature 512(7512), 61 (2014).

    CAS  Google Scholar 

  95. 95.

    S. Esconjauregui, B.C. Bayer, M. Fouquet, C.T. Wirth, C. Ducati, S. Hofmann, and J. Robertson: Growth of high-density vertically aligned arrays of carbon nanotubes by plasma-assisted catalyst pretreatment. Appl. Phys. Lett. 95(17), 173115 (2009).

    Google Scholar 

  96. 96.

    M. Bedewy, B. Farmer, and A.J. Hart: Synergetic chemical coupling controls the uniformity of carbon nanotube microstructure growth. ACS Nano 8(6), 5799 (2014).

    CAS  Google Scholar 

  97. 97.

    M. De Volder, S. Park, S. Tawfick, and A.J. Hart: Strain-engineered manufacturing of freeform carbon nanotube microstructures. Nat. Commun. 5, 4512 (2014).

    Google Scholar 

  98. 98.

    D.N. Futaba, K. Hata, T. Yamada, K. Mizuno, M. Yumura, and S. Iijima: Kinetics of water-assisted single-walled carbon nanotube synthesis revealed by a time-evolution analysis. Phys. Rev. Lett. 95(5), 056104 (2005).

    Google Scholar 

  99. 99.

    A.I. La Cava, C.A. Bernardo, and D.L. Trimm: Studies of deactivation of metals by carbon deposition. Carbon 20(3), 219 (1982).

    Google Scholar 

  100. 100.

    S.M. Kim, C.L. Pint, P.B. Amama, D.N. Zakharov, R.H. Hauge, B. Maruyama, and E.A. Stach: Evolution in catalyst morphology leads to carbon nanotube growth termination. J. Phys. Chem. Lett. 1(6), 918 (2010).

    CAS  Google Scholar 

  101. 101.

    R.G. de Villoria, S.L. Figueredo, A.J. Hart, S.A. Steiner, A.H. Slocum, and B.L. Wardle: High-yield growth of vertically aligned carbon nanotubes on a continuously moving substrate. Nanotechnology 20(40), 405611 (2009).

    Google Scholar 

  102. 102.

    S.N. Yoshikawa, T. Asari, N. Kishi, S. Hayashi, T. Sugai, and H. Shinohara: An efficient fabrication of vertically aligned carbon nanotubes on flexible aluminum foils by catalyst-supported chemical vapor deposition. Nanotechnology 19(24), 245607 (2008).

    Google Scholar 

  103. 103.

    Y. Zhou, L. Hu, and G. Grüner: A method of printing carbon nanotube thin films. Appl. Phys. Lett. 88(12), 123109 (2006).

    Google Scholar 

  104. 104.

    L. Ge, S. Sethi, L. Ci, P.M. Ajayan, and A. Dhinojwala: Carbon nanotube-based synthetic gecko tapes. Proc. Natl. Acad. Sci. 104(26), 10792 (2007).

    CAS  Google Scholar 

  105. 105.

    S. Tawfick, K. O’Brien, and A.J. Hart: Flexible high-conductivity carbon-nanotube interconnects made by rolling and printing. Small 5(21), 2467 (2009).

    CAS  Google Scholar 

Download references

Author information



Corresponding author

Correspondence to Mostafa Bedewy.

Rights and permissions

This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (, which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Bedewy, M. Data-driven understanding of collective carbon nanotube growth by in situ characterization and nanoscale metrology. Journal of Materials Research 32, 153–165 (2017).

Download citation