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Evaluation of the nanotube intrinsic resistance across the tip-carbon nanotube-metal substrate junction by Atomic Force Microscopy.

Dominiczak M, Otubo L, Alamarguy D, Houzé F, Volz S, Noël S, Bai J - Nanoscale Res Lett (2011)

Bottom Line: For negative tip-substrate bias, a systematic degradation in color and contrast of the electrical cartography occurs, consisting of an important and non-reversible increase of the measured resistance.This effect is attributed to the oxidation of some amorphous carbon areas scattered over the diamond layer covering the tip.For a direct polarization, the CNT and substrate surface can in turn be modified by an oxidation mechanism.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lab, MSSMat, UMR CNRS 8579, Ecole Centrale Paris, Grande Voie des Vignes, Châtenay-Malabry 92290, France. frederic.houze@supelec.fr.

ABSTRACT
Using an atomic force microscope (AFM) at a controlled contact force, we report the electrical signal response of multi-walled carbon nanotubes (MWCNTs) disposed on a golden thin film. In this investigation, we highlight first the theoretical calculation of the contact resistance between two types of conductive tips (metal-coated and doped diamond-coated), individual MWCNTs and golden substrate. We also propose a circuit analysis model to schematize the «tip-CNT-substrate» junction by means of a series-parallel resistance network. We estimate the contact resistance R of each contribution of the junction such as Rtip-CNT, RCNT-substrate and Rtip-substrate by using the Sharvin resistance model. Our final objective is thus to deduce the CNT intrinsic radial resistance taking into account the calculated electrical resistance values with the global resistance measured experimentally. An unwished electrochemical phenomenon at the tip apex has also been evidenced by performing measurements at different bias voltages with diamond tips. For negative tip-substrate bias, a systematic degradation in color and contrast of the electrical cartography occurs, consisting of an important and non-reversible increase of the measured resistance. This effect is attributed to the oxidation of some amorphous carbon areas scattered over the diamond layer covering the tip. For a direct polarization, the CNT and substrate surface can in turn be modified by an oxidation mechanism.

No MeSH data available.


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(a1, a2) AFM topographic images (1 × 1 μm2) of a CNT functionalized with AuNPs, obtained with a Pt/Ir and a diamond tip, respectively; (b1, b2) CNT height profile along dotted lines; (c1, c2) corresponding electrical maps; (d1, d2) distribution histograms of resistance values measured in the region marked out by a rectangle on the CNT. Same experimental parameters as for Figure 1.
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Figure 2: (a1, a2) AFM topographic images (1 × 1 μm2) of a CNT functionalized with AuNPs, obtained with a Pt/Ir and a diamond tip, respectively; (b1, b2) CNT height profile along dotted lines; (c1, c2) corresponding electrical maps; (d1, d2) distribution histograms of resistance values measured in the region marked out by a rectangle on the CNT. Same experimental parameters as for Figure 1.

Mentions: Besides these measurements on 'raw' CNTs, a series of tests on CNTs functionalized with AuNPs was also carried out in order to see if electrical properties of the CNTs could be modified. AuNPs are produced with a few drops of DDAB (didodecyldimethylammonium bromide) type organic molecule, introduced to reticulate the nanoparticles to CNTs by covalent bonds (micellar system). The particle size is about 5 nm. Figures 2a1 and 2a2 show topography views of a CNT with an AuNPs attachment for a conductive Pt/Ir tip and a diamond tip, respectively, b1 and b2 the corresponding cross-sections along dotted lines, c1 and c2 the associated resistance images (always under +1 V bias) and d1 and d2 typical distribution histograms of the local resistances. The a2 topography obtained with a diamond tip has a better resolution, showing individual gold grains, than the one obtained on raw CNT. We did not measure any resistance reduction of the MWCNTs with a gold nanoparticle functionalization (Table 1). Grafting of AuNPs may not be uniformly distributed and disposed in large quantity along MWCNTs. We think that the AuNPs are not enough numerous to induce a modification of the global electrical properties with CP-AFM. One of the main problems of the measurement with the AFM tip is that an individual CNT can slide under the tip pressure [28]. This is why the CNT position has sometimes changed between two successive pictures and the observed area can be rid of nanoparticles due to tip scanning. Hence, CNTs with metal nanoparticles in our situation were not found to show an improved conductivity by CP-AFM measurements, but they allowed us to check the reproducibility of the results when varying voltage bias as will be seen further (see section 'DC voltage effects').


Evaluation of the nanotube intrinsic resistance across the tip-carbon nanotube-metal substrate junction by Atomic Force Microscopy.

Dominiczak M, Otubo L, Alamarguy D, Houzé F, Volz S, Noël S, Bai J - Nanoscale Res Lett (2011)

(a1, a2) AFM topographic images (1 × 1 μm2) of a CNT functionalized with AuNPs, obtained with a Pt/Ir and a diamond tip, respectively; (b1, b2) CNT height profile along dotted lines; (c1, c2) corresponding electrical maps; (d1, d2) distribution histograms of resistance values measured in the region marked out by a rectangle on the CNT. Same experimental parameters as for Figure 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211423&req=5

Figure 2: (a1, a2) AFM topographic images (1 × 1 μm2) of a CNT functionalized with AuNPs, obtained with a Pt/Ir and a diamond tip, respectively; (b1, b2) CNT height profile along dotted lines; (c1, c2) corresponding electrical maps; (d1, d2) distribution histograms of resistance values measured in the region marked out by a rectangle on the CNT. Same experimental parameters as for Figure 1.
Mentions: Besides these measurements on 'raw' CNTs, a series of tests on CNTs functionalized with AuNPs was also carried out in order to see if electrical properties of the CNTs could be modified. AuNPs are produced with a few drops of DDAB (didodecyldimethylammonium bromide) type organic molecule, introduced to reticulate the nanoparticles to CNTs by covalent bonds (micellar system). The particle size is about 5 nm. Figures 2a1 and 2a2 show topography views of a CNT with an AuNPs attachment for a conductive Pt/Ir tip and a diamond tip, respectively, b1 and b2 the corresponding cross-sections along dotted lines, c1 and c2 the associated resistance images (always under +1 V bias) and d1 and d2 typical distribution histograms of the local resistances. The a2 topography obtained with a diamond tip has a better resolution, showing individual gold grains, than the one obtained on raw CNT. We did not measure any resistance reduction of the MWCNTs with a gold nanoparticle functionalization (Table 1). Grafting of AuNPs may not be uniformly distributed and disposed in large quantity along MWCNTs. We think that the AuNPs are not enough numerous to induce a modification of the global electrical properties with CP-AFM. One of the main problems of the measurement with the AFM tip is that an individual CNT can slide under the tip pressure [28]. This is why the CNT position has sometimes changed between two successive pictures and the observed area can be rid of nanoparticles due to tip scanning. Hence, CNTs with metal nanoparticles in our situation were not found to show an improved conductivity by CP-AFM measurements, but they allowed us to check the reproducibility of the results when varying voltage bias as will be seen further (see section 'DC voltage effects').

Bottom Line: For negative tip-substrate bias, a systematic degradation in color and contrast of the electrical cartography occurs, consisting of an important and non-reversible increase of the measured resistance.This effect is attributed to the oxidation of some amorphous carbon areas scattered over the diamond layer covering the tip.For a direct polarization, the CNT and substrate surface can in turn be modified by an oxidation mechanism.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lab, MSSMat, UMR CNRS 8579, Ecole Centrale Paris, Grande Voie des Vignes, Châtenay-Malabry 92290, France. frederic.houze@supelec.fr.

ABSTRACT
Using an atomic force microscope (AFM) at a controlled contact force, we report the electrical signal response of multi-walled carbon nanotubes (MWCNTs) disposed on a golden thin film. In this investigation, we highlight first the theoretical calculation of the contact resistance between two types of conductive tips (metal-coated and doped diamond-coated), individual MWCNTs and golden substrate. We also propose a circuit analysis model to schematize the «tip-CNT-substrate» junction by means of a series-parallel resistance network. We estimate the contact resistance R of each contribution of the junction such as Rtip-CNT, RCNT-substrate and Rtip-substrate by using the Sharvin resistance model. Our final objective is thus to deduce the CNT intrinsic radial resistance taking into account the calculated electrical resistance values with the global resistance measured experimentally. An unwished electrochemical phenomenon at the tip apex has also been evidenced by performing measurements at different bias voltages with diamond tips. For negative tip-substrate bias, a systematic degradation in color and contrast of the electrical cartography occurs, consisting of an important and non-reversible increase of the measured resistance. This effect is attributed to the oxidation of some amorphous carbon areas scattered over the diamond layer covering the tip. For a direct polarization, the CNT and substrate surface can in turn be modified by an oxidation mechanism.

No MeSH data available.


Related in: MedlinePlus