Effects of the electrical conductivity and orientation of silicon substrate on the synthesis of multi-walled carbon nanotubes by thermal chemical vapor deposition

Choi, Hong‐Seok; Gong, Jaeseok; Lim, Yeongjin; Im, Ki Hong; Jeon, Minhyon

doi:10.1186/1556-276x-8-110

Cited by 11 publications

(4 citation statements)

References 16 publications

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“…The lower mode in the bimodal distribution is attributed to particles formed around the grain boundaries, where the crystal facets are expected to vary. This is in agreement with literature[62], in which smaller particles…”

supporting

confidence: 94%

Integrating carbon nanotube forests into polysilicon MEMS: Growth kinetics, mechanisms, and adhesion

Ubnoske

Radauscher

Meshot

et al. 2017

Carbon

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The growth of carbon nanotubes (CNTs) on polycrystalline silicon substrates was studied to improve the design of CNT field emission sources for microelectromechanical systems (MEMS) applications and vacuum microelectronic devices (VMDs). Microwave plasmaenhanced chemical vapor deposition (PECVD) was used for CNT growth, resulting in CNTs that incorporate the catalyst particle at their base. The kinetics of CNT growth on polysilicon were compared to growth on Si (100) using the model of Deal and Grove, finding activation energies of 1.61 and 1.54 eV for the nucleation phase of growth and 1.90 and 3.69 eV for the diffusion-limited phase on Si (100) and polysilicon, respectively. Diffusivity values for growth on polysilicon were notably lower than the corresponding values on Si (100) and the growth process became diffusion-limited earlier. Evidence favors a surface diffusion growth mechanism involving diffusion of carbon precursor species along the length of the CNT forest to the catalyst at the base. Explanations for the differences in activation energies and diffusivities were elucidated by SEM analysis of the catalyst nanoparticle arrays and through wide-angle X-ray scattering (WAXS) of CNT forests. Finally, methods are presented to improve adhesion of CNT films during operation as field emitters, resulting in a 2.5x improvement.

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supporting

confidence: 94%

Integrating carbon nanotube forests into polysilicon MEMS: Growth kinetics, mechanisms, and adhesion

Ubnoske

Radauscher

Meshot

et al. 2017

Carbon

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“…Therefore, among the samples containing 30 nm TCOs, the differences in their NPs kinetics during annealing cannot be attributed to the roughness variation. Such differences are more likely caused by the distinct TCOs thermal conductivity, , which is directly related to the electrical conductivity, σ, presented in Table .…”

Section: Resultsmentioning

confidence: 99%

Influence of the Substrate on the Morphology of Self-Assembled Silver Nanoparticles by Rapid Thermal Annealing

et al. 2016

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Metal nanoparticles are of great interest for light trapping in photovoltaics. They are usually incorporated in the rear electrode of solar cells, providing strong light scattering at their surface plasmon resonances.In most cases, the nanoparticles are self-assembled by solid-state dewetting over a transparent conductive oxide (TCO) layer incorporated in the cell's rear electrode. Up to now, this process has been optimized mainly by tuning the thermal annealing parameters responsible for dewetting, or the thickness of the precursor metallic layer; but little attention has been paid to the influence of the underlying TCO layer properties on the morphology of the nanoparticles formed, which is the focus of the present article. This work investigates Ag nanoparticles structures produced on distinct surfaces by a simple, fast and highly reproducible method employing rapid thermal annealing. The results indicate that both the thermal conductivity and surface roughness of the TCO layer play a determinant role on the morphology of the nanostructures formed. This is of particular relevance, since we show in the study performed that the parasitic absorption of these Ag nanostructures is reduced, while the scattering is enhanced when the Ag nanostructures are formed on TCO layers with the highest conductivity and the lowest surface roughness (∼1 nm). These results unveil novel possibilities for the improvement of plasmonic nanostructures fabricated by thermal dewetting, via the careful adjustment of the physical properties of the underlying surface.

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“…They are either semiconducting or metallic [ 8 ]. Because of the high aspect ratio and good conductivity, MWCNTs are especially promising as conductive fillers for making polymeric composites with high-strength and electric-shielding properties [ 9 – 11 ].…”

Section: Introductionmentioning

confidence: 99%

Integrated Analysis of Dysregulated ncRNA and mRNA Expression Profiles in Humans Exposed to Carbon Nanotubes

et al. 2016

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BackgroundAs the application of carbon nanotubes (CNT) in consumer products continues to rise, studies have expanded to determine the associated risks of exposure on human and environmental health. In particular, several lines of evidence indicate that exposure to multi-walled carbon nanotubes (MWCNT) could pose a carcinogenic risk similar to asbestos fibers. However, to date the potential markers of MWCNT exposure are not yet explored in humans.MethodsIn the present study, global mRNA and ncRNA expression profiles in the blood of exposed workers, having direct contact with MWCNT aerosol for at least 6 months (n = 8), were compared with expression profiles of non-exposed (n = 7) workers (e.g., professional and/or technical staff) from the same manufacturing facility.ResultsSignificant changes in the ncRNA and mRNA expression profiles were observed between exposed and non-exposed worker groups. An integrative analysis of ncRNA-mRNA correlations was performed to identify target genes, functional relationships, and regulatory networks in MWCNT-exposed workers. The coordinated changes in ncRNA and mRNA expression profiles revealed a set of miRNAs and their target genes with roles in cell cycle regulation/progression/control, apoptosis and proliferation. Further, the identified pathways and signaling networks also revealed MWCNT potential to trigger pulmonary and cardiovascular effects as well as carcinogenic outcomes in humans, similar to those previously described in rodents exposed to MWCNTs.ConclusionThis study is the first to investigate aberrant changes in mRNA and ncRNA expression profiles in the blood of humans exposed to MWCNT. The significant changes in several miRNAs and mRNAs expression as well as their regulatory networks are important for getting molecular insights into the MWCNT-induced toxicity and pathogenesis in humans. Further large-scale prospective studies are necessary to validate the potential applicability of such changes in mRNAs and miRNAs as prognostic markers of MWCNT exposures in humans.

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Effects of the electrical conductivity and orientation of silicon substrate on the synthesis of multi-walled carbon nanotubes by thermal chemical vapor deposition

Cited by 11 publications

References 16 publications

Integrating carbon nanotube forests into polysilicon MEMS: Growth kinetics, mechanisms, and adhesion

Integrating carbon nanotube forests into polysilicon MEMS: Growth kinetics, mechanisms, and adhesion

Influence of the Substrate on the Morphology of Self-Assembled Silver Nanoparticles by Rapid Thermal Annealing

Integrated Analysis of Dysregulated ncRNA and mRNA Expression Profiles in Humans Exposed to Carbon Nanotubes

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