Limits...
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.


Related in: MedlinePlus

(a1, a2) AFM topographic images (1 × 1 μm2) of a 'raw' CNT 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. The cantilever load-force was about 16 to 80 nN, respectively, for k = 1 to 5 N/m. Vtip-sample = +1 V.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211423&req=5

Figure 1: (a1, a2) AFM topographic images (1 × 1 μm2) of a 'raw' CNT 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. The cantilever load-force was about 16 to 80 nN, respectively, for k = 1 to 5 N/m. Vtip-sample = +1 V.

Mentions: Figures 1a1 and 1a2 show typical topographic AFM images (1 × 1 μm2) of a MWCNT obtained with a Pt/Ir tip and a diamond tip, respectively; b1 and b2 show typical cross-sections along the dotted lines; c1 and c2 show the associated electrical cartographies of the CNT (+1 V bias) and d1 and d2 show the corresponding distribution histogram of the local resistances R measured within a rectangle selected along the CNT. The CNT diameter can be estimated by considering the height profile in the topography images. With the diamond tip, the CNT has an apparent width larger than its height in the topographic view as well as in the resistance image. However, the image width obtained with a Pt/Ir tip gives a value closer to the real CNT diameter. The contact area of the Pt/Ir tip is very small compared to the diamond tip, which does not have a perfect tetrahedral geometry due to the coating morphology. One can be convinced looking at microscopy images on the manufacturer's website [25]. The MWCNTs observed by high resolution TEM have an average of 30 to 40 walls with an external diameter in the 15 to 40 nm range. These values are in accordance with the AFM observations, since from the scanned CNTs in Figure 1 nominal diameter can be estimated between 20 and 35 nm. The average roughness Ra on the substrate surface is given on the topographic images. For more clarity, the topography images were fitted in plane and then the structures were raised using an arithmetic mean in a 5 × 5 matrix.


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 'raw' CNT 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. The cantilever load-force was about 16 to 80 nN, respectively, for k = 1 to 5 N/m. Vtip-sample = +1 V.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: (a1, a2) AFM topographic images (1 × 1 μm2) of a 'raw' CNT 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. The cantilever load-force was about 16 to 80 nN, respectively, for k = 1 to 5 N/m. Vtip-sample = +1 V.
Mentions: Figures 1a1 and 1a2 show typical topographic AFM images (1 × 1 μm2) of a MWCNT obtained with a Pt/Ir tip and a diamond tip, respectively; b1 and b2 show typical cross-sections along the dotted lines; c1 and c2 show the associated electrical cartographies of the CNT (+1 V bias) and d1 and d2 show the corresponding distribution histogram of the local resistances R measured within a rectangle selected along the CNT. The CNT diameter can be estimated by considering the height profile in the topography images. With the diamond tip, the CNT has an apparent width larger than its height in the topographic view as well as in the resistance image. However, the image width obtained with a Pt/Ir tip gives a value closer to the real CNT diameter. The contact area of the Pt/Ir tip is very small compared to the diamond tip, which does not have a perfect tetrahedral geometry due to the coating morphology. One can be convinced looking at microscopy images on the manufacturer's website [25]. The MWCNTs observed by high resolution TEM have an average of 30 to 40 walls with an external diameter in the 15 to 40 nm range. These values are in accordance with the AFM observations, since from the scanned CNTs in Figure 1 nominal diameter can be estimated between 20 and 35 nm. The average roughness Ra on the substrate surface is given on the topographic images. For more clarity, the topography images were fitted in plane and then the structures were raised using an arithmetic mean in a 5 × 5 matrix.

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