Electronic properties of multiwalled carbon nanotubes in an embedded vertical array

Li, Jun; Stevens, R.; Delzeit, Lance; Ng, Hou T.; Cassell, Alan M.; Han, Jie; Meyyappan, M.

doi:10.1063/1.1496494

Cited by 157 publications

(114 citation statements)

References 22 publications

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“…Average CNT height and diameter were determined using scanning electron microscopy (SEM) to be approximately 5-8 µm and 100 nm, respectfully. A complete characterization of the growth process has been previously reported [4][5][6][7][8]. shows a cross-section of the CNT array after completion of the fabrication process.…”

Section: Cnt Nanoarray Electrodesmentioning

confidence: 99%

“…(2), (3), (4), and (6). A variety of O 2 etch times were tested to achieve the desired tip to tip separation distance of approximately 1 µm measured using SEM (figure 4).…”

Section: Cnt Nanoarray Electrodesmentioning

confidence: 99%

“…K 3 Fe(CN) 6 was used as received from SigmaAldrich (St Louis, MO). Stock solution of 100 mM K 3 Fe(CN) 6 in 0.1 M KCl was diluted with additional 0.1 M KCl to obtain the desired concentrations of K 3 Fe(CN) 6 .…”

Section: Electrochemical Characterizationmentioning

confidence: 99%

“…The CNT nanoarrays were electrochemically characterized by cyclic voltammetry in 5.0 mM K 3 Fe(CN) 6 with 0.1 M KCl at a scan rate of 100 mV s −1 . The anodic and cathodic peak separation ( E p ) was used as the figure of merit for comparison of electrode performance.…”

Section: Electrochemical Characterizationmentioning

confidence: 99%

“…The vertical carbon nanotubes must be encased in a stabilizing matrix prior to the fabrication of the microfluidic channels that will deliver the analyte. In the past, thermal chemical vapour deposition (CVD) of tetraethylorthosilicate (TEOS) has been used as a stabilizing matrix, which requires the use of chemical mechanical polishing (CMP) to planarize the electrode surface and expose the tips of the carbon nanotubes [4][5][6][7][8]. The high temperature CVD TEOS process and accompanying CMP can make this technique expensive, time consuming, and incompatible with other processing requirements for on-chip fluidic channels.…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical characterization of parylene-embedded carbon nanotube nanoelectrode arrays

et al. 2006

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A novel parylene-embedded carbon nanotube nanoelectrode array is presented for use as an electrochemical detector working electrode material. The fabrication process is compatible with standard microfluidic and other MEMS processing without requiring chemical mechanical polishing. Electrochemical studies of the nanoelectrodes showed that they perform comparably to platinum. Electrochemical pretreatment for short periods of time was found to further improve performance as measured by cathodic and anodic peak separation of K 3 Fe(CN) 6 . A lower detection limit below 0.1 µM was measured and with further fabrication improvements detection limits between 100 pM and 10 nM are possible. This makes the nanoelectrode arrays particularly suitable for trace electrochemical analysis.

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Section: Cnt Nanoarray Electrodesmentioning

confidence: 99%

“…(2), (3), (4), and (6). A variety of O 2 etch times were tested to achieve the desired tip to tip separation distance of approximately 1 µm measured using SEM (figure 4).…”

Section: Cnt Nanoarray Electrodesmentioning

confidence: 99%

Section: Electrochemical Characterizationmentioning

confidence: 99%

Section: Electrochemical Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrochemical characterization of parylene-embedded carbon nanotube nanoelectrode arrays

et al. 2006

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Carbon Nanotube–Based Sensors and Biosensors

Compton

Wildgoose

Wong

2009

Biosensing Using Nanomaterials

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Arrays of Heterojunctions of Ag Nanowires and Amorphous Carbon Nanotubes

et al. 2004

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One-dimensional (1D) metal±semiconductor (M/S) heterojunctions with ohmic current±voltage (I±V) characteristics are important to nanodevices because of their necessity in interconnection and packaging. However, it is often the case that Schottky, not ohmic contacts, occur in 1D M/S heterojunctions. [1][2][3][4] In our experiments, we have synthesized arrays of 1D heterojunctions of Ag nanowires (AgNWs) and amorphous carbon nanotubes (a-CNTs), using an approach developed in our group. [5,6] In the 1D heterojunctions, the a-CNTs are contacted ohmically by the AgNWs. This is based on general characteristics of the electronic structure of amorphous semiconductors, which cause contacts between metals and most amorphous semiconductors to be ohmic. [7,8] Therefore, if 1D amorphous semiconductor materials are used as intermediates in interconnection and packaging, a basis can be established for designing ohmic contacts in nanodevices by using a variety of materials.Figures 1a,b show scanning electron microscopy (SEM) images of the cross-section and the top view, respectively, of an AgNW/a-CNT heterojunction array in an anodic aluminum oxide (AAO) template. The AgNW and the a-CNT parts are about 7.2 lm and 32.7 lm in length, respectively. The a-CNTs could be made to protrude from the AAO template, as shown in Figure 1b, only after the AAO template surface had been etched slightly. Their diameters were 40±64 nm, with a dominant value of 51±5 nm (about 80 % were in this range). Figure 2a shows a transmission electron microscopy (TEM) image of a heterojunction node. Its corresponding electron diffraction pattern and high-resolution TEM (HRTEM) image are shown in Figures 2b,c, respectively. In Figure 2b, in addition to single-crystal diffraction spots indexed as face-centered cubic Ag (fcc(Ag)), some faint rings and arcs exist that are too weak to be printed. These come from the amorphous part of the structure, which consists of many disordered tiny carbon clusters, as shown in the CNT part of Figure 2c. It is clear that each heterojunction consists of a single-crystal AgNW and an a-CNT that is composed of many tiny carbon clusters. The amorphous nature of the latter is due to its growth mechanism, which is based on self-catalytic functions of the AAO channels. [9] A resistance±temperature (R±T) curve and a C1s core-level X-ray photoelectron spectroscopy (XPS) spectrum from two arrays containing only a-CNTs are shown in Figures 3a,b, respectively. The R±T curve was acquired by using two electrical probes which were attached to the bottom and top surfaces of the AAO templateÐwhich contained a-CNTsÐusing evaporated Ag films. This method is similar to that described by Heremans et al. [10] From the R±T curve, it can be seen that the resistance increases gradually with decreasing temperature, which is one of the characteristics of semiconductors. Additionally, considering the amorphous nature of our aCNTs, they could be further classified as amorphous semiconductors. The XPS spectrum indicates that the a-CNTs have an sp 2 fractio...

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Electronic properties of multiwalled carbon nanotubes in an embedded vertical array

Cited by 157 publications

References 22 publications

Electrochemical characterization of parylene-embedded carbon nanotube nanoelectrode arrays

Electrochemical characterization of parylene-embedded carbon nanotube nanoelectrode arrays

Carbon Nanotube–Based Sensors and Biosensors

Arrays of Heterojunctions of Ag Nanowires and Amorphous Carbon Nanotubes

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