Growth of Single-Walled Carbon Nanotubes Using Germanium Nanocrystals Formed by Implantation

Uchino, Toshitaka; Ayre, G. N.; Smith, David C.; Hutchison, J. L.; Groot, C. H. de; Ashburn, P.

doi:10.1149/1.3147248

Cited by 17 publications

(18 citation statements)

References 24 publications

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“…This leads to a new interpretation of the role of the catalyst particle in CNT growth, where only a nanoscale curvature is needed to act as a template for nanotube formation. This assertion is supported by the reports of CNT formation from semiconductor nanoparticles (Takagi et al, 2007;Uchino et al, 2009;2005b), from which no catalytic functions were expected. The first reports of CNT growth from semiconducting catalysts were by Uchino et al (2005b).…”

Section: Semiconductor Nanoparticle Catalystsmentioning

confidence: 60%

“…In this model, hydrocarbons adsorbed on the metal nanoparticle are catalytically decomposed resulting in atomic carbon dissolving into the liquid catalyst particle, and when a supersaturated state is reached, carbon precipitates in a tubular, crystalline form. Recently, several groups have reported successful growth of CNTs from noble metal (Lee et al, 2005;Takagi et al, 2006;Yoshihara et al, 2008;Yuan et al, 2008;Zhou et al, 2006), ceramic (Liu et al, 2008b;Steiner et al, 2009) and semiconducting nanoparticles (Takagi et al, 2007;Uchino et al, 2009;2005b), all of which are regarded as unable to catalyse the dissociation of hydrocarbons. In addition to this, in their bulk form, these materials do not have a catalytic function to produce graphite.…”

Section: Introductionmentioning

confidence: 99%

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Chemical Vapour Deposition of CNTs Using Structural Nanoparticle Catalysts

Ayre¹,

Uchino²,

Mazumder³

et al. 2010

Carbon Nanotubes

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Section: Semiconductor Nanoparticle Catalystsmentioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Chemical Vapour Deposition of CNTs Using Structural Nanoparticle Catalysts

Ayre¹,

Uchino²,

Mazumder³

et al. 2010

Carbon Nanotubes

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“…This is surprising given that we would expect Ge nanoparticles with diameters less than 5 nm to be necessary for the growth of SWNTs. 15) Figure 9(b) shows a HRTEM image of the early stage of CNT growth [indicated by arrow in Fig. 9(b)], indicating that CNTs start to grow from an amorphous structure on the surface of the sample.…”

Section: Carbon Nanotubes Grown From Ge Nanostructuresmentioning

confidence: 99%

Metal-Catalyst-Free Growth of Silica Nanowires and Carbon Nanotubes Using Ge Nanostructures

Uchino

Hutchison

Ayre

et al. 2011

Jpn. J. Appl. Phys.

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The use of Ge nanostructures is investigated for the metal-catalyst-free growth of silica nanowires and carbon nanotubes (CNTs). Silica nanowires with diameters of 10-50 nm and lengths of ≤ 1 µm were grown from SiGe islands, Ge dots, and Ge nanoparticles. High-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) reveal that the nanowires grow from oxide nanoparticles on the sample surface. We propose that the growth mechanism is thermal diffusion of oxide through the GeO 2 nanostructures. CNTs with diameters 0.6-2.5 nm and lengths of less than a few µm were similarly grown by chemical vapor deposition from different types of Ge nanostructures. Raman measurements show the presence of radial breathing mode peaks and the absence of the disorder induced D-band, indicating single walled CNTs with a low defect density. HRTEM images reveal that the CNTs also grow from oxide nanoparticles, comprising a mixture of GeO 2 and SiO 2

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“…CNTs can clearly be seen, together with shorter and thicker nanowires, which have been shown to be silica nanowires in our 3 earlier work. 8,10 The area density of CNTs was analyzed using several FE-SEM images from different parts of the wafer and evaluated as 3.0 CNTs/µm 2 . …”

mentioning

confidence: 99%

“…Several different metal-catalyst-free growth methods of CNTs have been reported, [6][7][8][9][10][11][12] including our earlier work on CNT growth from Ge nanoparticles. 8,10 However to date, no device results have been reported for CNTFETs produced by any of the metal-catalyst-free CNT growth methods, mainly because it has not been possible to grow CNTs on a suitable insulator without a metal catalyst.…”

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confidence: 99%

Metal-Catalyst-Free Growth of Carbon Nanotubes and Their Application in Field-Effect Transistors

Uchino¹,

Ayre²,

Smith³

et al. 2011

Electrochem. Solid-State Lett.

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Abstract:The metal-catalyst-free growth of carbon nanotubes (CNTs) using chemical vapor deposition and the application in field-effect transistors (FETs) is demonstrated. The CNT growth process used a 3-nm-thick Ge layer on SiO 2 that was subsequently annealed to produce Ge nanoparticles. Raman measurements show the presence of radial breathing mode peaks and the absence of the disorder induced D-band, indicating single walled CNTs with a low defect density. The synthesized CNTs are used to fabricate CNTFETs and the best device has a state-of-the-art on/off current ratio of 3×10 8 ExperimentalA p + Si substrate (0.005 Ω·cm) was employed as a back gate and a 45-nm-thick thermally grown SiO 2 layer was employed as a gate dielectric. A 3-nm-thick Ge layer was deposited by either sputtering or evaporation on the SiO 2 layer. The nanoparticles on the insulator were formed at 850°C for 10 min in a mixture of Ar (1000 sccm) and H 2 (300 sccm) after a preanneal in H 2 (1000 sccm) at 950°C. The samples were reloaded to a hot-wall reactor and then CNT growth was performed using chemical vapor deposition (CVD) at atmospheric pressure.CNTs were grown at 850°C for 10 min using a mixture of methane (1000 sccm) and H 2 (300 sccm) immediately after a pre-anneal in H 2 (1000 sccm) at 900°C. Back gate CNTFETs were fabricated with Pd source/drain contacts. Pd was deposited by sputtering and the source/drain electrodes were formed using direct write laser lithography and lift-off. The gap between Pd source/drain electrodes was 2.0 µm and the width was 8.0 µm. Typically only one or two CNTs crossed over the 2.0 µm gap between the source and drain. Electrical characteristics of CNTFETs were measured in ambient air. Raman spectra were obtained using He-Ne (632.8 nm) laser excitation. Figure 1a shows the particle height distribution after nanoparticle formation obtained from atomic force microscopy (AFM) measurements. Line analysis shows that the peak particle count occurs at a particle height of 1.4 ± 0.8 nm and area analysis gives a mean particle density of 450 ± 20 particles/µm 2 . Figure 1b shows a typical field emission scanning electron microscope (FE-SEM) image after CNT growth. CNTs can clearly be seen, together with shorter and thicker nanowires, which have been shown to be silica nanowires in our 3 earlier work. 8,10 The area density of CNTs was analyzed using several FE-SEM images from different parts of the wafer and evaluated as 3.0 CNTs/µm 2 . Results and DiscussionEnergy dispersive X-ray spectroscopy analysis indicates that the nanoparticles contain a mixture of Ge, Si, and O. 13 In order to investigate the origins of the oxygen, CNTs were grown without air exposure after the Ar/H 2 anneal. The observed area density of CNT was 3.4CNTs/µm 2 , compared with 3.0 CNTs/µm 2 after air exposure, which indicates that air exposure has no significant effect. This result suggests that the oxygen in the nanoparticles comes from the SiO 2 substrate in this case. These and earlier results 11,12 suggest the following mechanism for CNT...

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Growth of Single-Walled Carbon Nanotubes Using Germanium Nanocrystals Formed by Implantation

Cited by 17 publications

References 24 publications

Chemical Vapour Deposition of CNTs Using Structural Nanoparticle Catalysts

Chemical Vapour Deposition of CNTs Using Structural Nanoparticle Catalysts

Metal-Catalyst-Free Growth of Silica Nanowires and Carbon Nanotubes Using Ge Nanostructures

Metal-Catalyst-Free Growth of Carbon Nanotubes and Their Application in Field-Effect Transistors

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