Hydrogenation of Single-Walled Carbon Nanotubes

Nikitin, Anton; Ogasawara, Hirohito; Mann, David J.; Denecke, R.; Zhang, Zhiyong; Dai, Hongjie; Cho, K.; Nilsson, Anders

doi:10.1103/physrevlett.95.225507

Cited by 248 publications

(206 citation statements)

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“…Ruffieux et al 5 reported a saturation in H uptake after 200 s, leveling off at 50% capacity. Nikitin et al 7 exposed several films of SWCNTs to an atomic hydrogen beam and measured storage capacities of 65% and of 30% and close to 100%. 9 In Ref.…”

Section: ͑1͒mentioning

confidence: 99%

“…Both physisorption ͑H 2 -CNT van der Waals interactions͒ and chemisorption ͑formation of stable sp 3 C-H bonds͒ mechanisms have been accounted for hydrogen adsorption on CNTs. Chemisorption of H atoms ͑generated, e.g., in a H 2 plasma͒ has been shown to provide storage capacities as high as 7 wt %, [3][4][5][6][7][8][9][10] close to the theoretical value of 7.7 wt %, corresponding to a CNT containing one chemisorbed H atom per C atom. The measured storage capacities based on this approach varied among different studies; [3][4][5][6][7][8][9][10] this discrepancy is also due to particular features of the sample used including CNT diameter distribution and bundle density 9 and source of H atoms.…”

mentioning

confidence: 99%

“…This model provides experimentally testable hypotheses which can be used to explain the observed storage capacities for bundles of SWCNTs. 7,9,10 For a more detailed consideration of H mass transfer limitations in SWCNT bundles, we represent the bundle as a regular array of SWCNTs of equal diameter in their pristine state as depicted in Fig. 1͑a͒.…”

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On the hydrogen storage capacity of carbon nanotube bundles

Muniz

Meyyappan

Maroudas

2009

Applied Physics Letters

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An analytical model is presented to describe the effect of carbon nanotube (CNT) swelling upon hydrogenation on the hydrogen storage capacity of single-walled CNT bundles; the model is properly parameterized using atomistic calculations for the relationship between CNT swelling and the degree of hydrogenation as measured by the coverage of the CNTs by chemisorbed atomic H. The model generates experimentally testable hypotheses, which can be used to explain the lower H storage capacities reported for CNT bundles and the experimentally observed nonuniformity of hydrogenation of CNT bundles.

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Section: ͑1͒mentioning

confidence: 99%

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On the hydrogen storage capacity of carbon nanotube bundles

Muniz

Meyyappan

Maroudas

2009

Applied Physics Letters

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“…The sub-threshold characteristics show an excellent I mll o ff ratio of 10 5 and a reasonably steep sub-threshold slope of 130 mVIdec. The output characteristic shows linear characteristics below electronic structure due to the stable covalent C-H bonding [10], [II]. In particular, the Hz could decrease the electron affinity of the CNTs, tending to produce p-FET behavior.…”

Section: R Esults and Discussionmentioning

confidence: 99%

Fe/Ge Catalyzed Carbon Nanotube Growth on HfO<sub>2</sub> for Nano-Sensor Applications

Uchino¹,

Ayre²,

Smith³

et al. 2009

Extended Abstracts of the 2009 International Conference on Solid State Devices and Materials

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Abstract-A carbon nanotube (CNT) growth process on Hf0 2 is reported for the first time for application in nano-sensors, The process uses a combination of Ge nanoparticles and ferric nitrate dispersion and achieves an increase in CNT density from 0.15 to 6.2 11m length/um" compared with the use of ferric nitrate dispersion alone. The growth process is validated by the fabrication of back-gate CNT field-effect transistors (CNTFETs) using AI source/drain (SID) contacts and a "2 anneal at 400°C.The transistors exhibit p-FET behavior with an Iml1offratio of 10 5 and a steep sub-threshold slope of 130 mY/dec. These results are rather sur prising, as earlier research in the literature on CNTFETs with AI SID electrodes showed n-FET behavior. The p-FET behavior is shown to be due to the H 2 anneal, which we ascribe to the smaller electron affinity of hydrogenised CNTs . Measurements of the temperature dependence of the drain current show low Schottky barrier height AI SID contacts after a "2 anneal, which tends to confirm this explanation. Recently, carbon nanotubes (CNTs) are gammg much attention for bio-sensing [1] because they offer the prospect real-time, label-free sensing for point-of-care diagnosis . The main advantage of CNTs for this application is a very high sensitivity due to the large surface to volume ratio of a carbon nanotube. The use of a high-x dielectric as a gate insulator for a CNT field-effect transistor (CNTF ET) is of interest because it delivers improved performance due to an increased l orlloffratio. CNTFETs with a HfD z gate dielectric have also recently been researched for application in high-speed CNT memories and a strong hysteresis effect has been observed [2]. CNTs can be introduced onto HfO z using dispersion techniques, but CNT growth by chemical vapor deposition (CYD) would be more compatible with mainstream silicon technology. However, CYD growth of CNTs on HfD z appears to be very difficult and to our knowledge no work has been reported on this topic to date.In this paper, a CNT growth process on HfO z is reported for the first time and this growth process is used to produce back gate CNTFETs with Al sourceldrain (SID) contacts. The novel growth process uses a combination of Ge nanoparticles and ferric nitrate dispersion to achieve a dramatic increase in CNT yield compared with the use of ferric nitrate dispersion alone. Electrical measurements on completed CNTFETs show p-FET behavior, an excellent l orlloff ratio of 105, and a steep sub-threshold slope of 130 mYIdec.978-1-4 244-4353-6 /09 /$ 25 .00 ©2 0 0 9 IEEE II. E XPERIMENTALA p" Si substrate (0.005 Q·cm) was employed as a back gate and a passivating SiOz layer was thermally grown, followed by the deposition of a HfO z layer by atomic-layer deposition, as shown in Fig.l . A 30nm SiOz layer was then deposited by plasma enhanced chemical vapor deposition (PECYD) on top of the HfO z and densified at 950°C. The SiOz layer was then implanted with s-ro" em", 20 keY Ge and annealed in N z at 600°C for 40 min to create Ge nanoparticles...

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“…This effect can be expected for both single vacancies and adatoms, as a single hydrogen adatom chemisorbed on top of a sp 2 -hybridized carbon atom should change the hybridization of the atom from the sp 2 -to a sp 3 -type and thus effectively remove the atom from the -electron network. Based on experimental data [5,6], one can conclude that such defects must be stable at the temperatures used for heat treatment.…”

Section: Comment On ''Paired Gap States In a Semiconducting Carbon Namentioning

confidence: 99%