Papers by philippe poncharal
The Journal of Physical Chemistry B, 2002
Multiwalled carbon nanotubes are shown to be ballistic conductors at room temperature, with mean ... more Multiwalled carbon nanotubes are shown to be ballistic conductors at room temperature, with mean free paths of the order of tens of microns. The measurements are performed both in air and in high vacuum in the transmission electron microscope on nanotubes that protrude from unprocessed arc-produced nanotube containing fibers which contact with a liquid metal surface. These experiments follow and extend the original experiments by Frank et al (Science, 280 1744 1998) that demonstrated for the first time the large current carrying capability, very low intrinsic resistivities, and evidence for quantized conductance. This indicated 1D transport, that only the surface layer contributes to the transport, and ballistic conduction at room temperature. Here we follow up on the original experiment including in-situ electron microscopy experiments and a detailed analysis of the length dependence of the resistance. The per unit length resistance ρ < 100 Ω/µm, indicating free paths l > 65 µm, unambiguously demonstrate ballistic conduction at room temperature up to macroscopic distances. The nanotube-metal contact resistances are in the range 0.1-1 kΩµm. Contact scattering can explain why the measured conductances are about half the expected theoretical value of 2 G 0 . For V>0.1V the conductance rises linearly (dG/dV~0.3 G 0 /V) reflecting the linear increase in the density-of-states in a metallic nanotube above the energy gap. Increased resistances (ρ =2-10 kΩ/µm) and anomalous I-V dependences result from impurities and surfactants on the tubes. Evidence is presented that ballistic transport occurs in undoped and undamaged tubes for which the top layer is metallic and the next layer is semiconducting. The diffusive properties of lithographically contacted multiwalled nanotubes most likely result from purification and other processing steps that damage and dope the nanotubes thereby making them structurally and electronically different than the pristine nanotubes investigated here.
Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada, 2000
Nanomaterials have attracted a great deal of research interest recently. The small size of nanost... more Nanomaterials have attracted a great deal of research interest recently. The small size of nanostructures constrains the applications of well-established testing and measurement techniques, thus new methods and approaches must be developed for quantitative measurement of the properties of individual nanostructures. This article reports our progress in using in situ transmission electron microscopy to measure the electrical, mechanical, and field-emission properties of individual carbon nanotubes whose microstructure is well-characterized. The bending modulus of a single carbon nanotube has been measured by an electric field-induced resonance effect. A nanobalance technique is demonstrated that can be applied to measure the mass of a tiny particle as light as 22 fg (1 fg = 10(-15) g), the smallest balance in the world. Quantum conductance was observed in defect-free nanotubes, which led to the transport of a superhigh current density at room temperature without heat dissipation. Fina...
Guest editor/Rédacteur en chef invité: Fabio Pistolesi
AFM and Raman Studies of Graphene Exfoliated on SiC
Materials Science Forum, 2009
We report an investigation of few layers graphene exfoliated on SiC. Using AFM and Raman spectros... more We report an investigation of few layers graphene exfoliated on SiC. Using AFM and Raman spectroscopy, we find that the graphene thickness determined from the normalized intensity of Raman lines significantly depart from the one obtained using XPS.
Science, 1999
Static and dynamic mechanical deflections were electrically induced in cantilevered, multiwalled ... more Static and dynamic mechanical deflections were electrically induced in cantilevered, multiwalled carbon nanotubes in a transmission electron microscope. The nanotubes were resonantly excited at the fundamental frequency and higher harmonics as revealed by their deflected contours, which correspond closely to those determined for cantilevered elastic beams. The elastic bending modulus as a function of diameter was found to decrease sharply (from about 1 to 0.1 terapascals) with increasing diameter (from 8 to 40 nanometers), which indicates a crossover from a uniform elastic mode to an elastic mode that involves wavelike distortions in the nanotube. The quality factors of the resonances are on the order of 500. The methods developed here have been applied to a nanobalance for nanoscopic particles and also to a Kelvin probe based on nanotubes.
Pure and Applied Chemistry, 2000
Property characterization of nanomaterials is challenged by the small size of the structure becau... more Property characterization of nanomaterials is challenged by the small size of the structure because of the difficulties in manipulation. Here we demonstrate a novel approach that allows a direct measurement of the mechanical and electrical properties of individual nanotube-like structures by in situ transmission electron microscopy (TEM). The technique is powerful in a way that it can be directly correlated to the atomic-scale microstructure of the carbon nanotube with its physical properties, thus providing a complete characterization of the nanotube. Applications of the technique will be demonstrated in measurements of the mechanical properties, the electron field emission, and the ballistic quantum conductance of individual carbon nanotubes. A nanobalance technique is demonstrated that can be applied to measure the mass of a single tiny particle as light as 22 fg (1 f = 10-15 ).
Comment on “Geometrical Dependence of High-Bias Current in Multiwalled Carbon Nanotubes”
Physical Review Letters, 2004
ABSTRACT A Comment on the Letter by B. Bourlon et al., Phys. Rev. Lett. 92, 026804 (2004). The au... more ABSTRACT A Comment on the Letter by B. Bourlon et al., Phys. Rev. Lett. 92, 026804 (2004). The authors of the Letter offer a Reply.
Physical Review B, 2009
The Raman spectral signature of folded graphene layers for one to six layers was studied. Folding... more The Raman spectral signature of folded graphene layers for one to six layers was studied. Folding allows realization of rotational disorder in otherwise perfect samples. We show that the two-dimensional Raman band of the folded sample is up shifted compared to the unfolded sample. The evolution of the spectral signature with increasing number of layers is discussed.
Physical Review B, 2008
We compare the main feature of the measured Raman scattering spectra from single layer graphene w... more We compare the main feature of the measured Raman scattering spectra from single layer graphene with a bilayer in which the two layers are arbitrarily misoriented. The profiles of the 2D bands are very similar having only one component, contrary to the four found for commensurate Bernal bilayers. These results agree with recent theoretical calculations and point to the similarity of the electronic structures of single layer graphene and misoriented bilayer graphene. Another new aspect is that the dependance of the 2D frequency on the laser excitation energy is different in these two latter systems.
Physical Review B, 2009
In their Comment, Ni et al. show new data as supporting their hypothesis, i.e., the two-dimension... more In their Comment, Ni et al. show new data as supporting their hypothesis, i.e., the two-dimensional band blueshift between graphene and misoriented bilayer is caused by a reduction in the Fermi velocity. In the first part of our reply, we will demonstrate that the exhibited data, which typically shows a constant blueshift for various excitation energies are in contradiction with a change in Fermi velocity. In the second part we will explain how charge transfer from the substrate that affects the phonon-dispersion curve can account for the observed discrepancies and how this hypothesis is supported by experimental observations.
Journal of Physics and Chemistry of Solids, 2000
Nanomaterials are a fundamental component of nanoscience and nanotechnology. The small size of na... more Nanomaterials are a fundamental component of nanoscience and nanotechnology. The small size of nanostructures constrains the applications of well-established testing and measurement techniques, thus new methods and approaches must be developed for synthesis, property characterization and device fabrication. This has been the focus of our research, aiming at exploring state-of-the-art techniques for materials processing and characterization. This paper reviews our progress in using in situ transmission electron microscopy to measure the electric, mechanical and field emission properties of individual carbon nanotubes with well-defined structures. Quantum conductance was observed in defect-free nanotubes, which led to the transport of a superhigh current density at room temperature without heat dissipation. A nanobalance technique is demonstrated that can be applied to measure the mass of a tiny particle as light as 22 fg 1 f 10 Ϫ15 :
Journal of Nanoscience and Nanotechnology, 2003
The European Physical Journal D, 1999
We present results of carbon nanotube conductance measurements. The experiments were performed us... more We present results of carbon nanotube conductance measurements. The experiments were performed using an scanning probe microscope (SPM) system where a carbon nanotube fiber is connected to the SPM tip and then lowered into a liquid mercury contact. Experiments were also performed using a modified transmission electron microscope (TEM) specimen holder supplied with piezo and micrometer positioning system. Thus the contacting process of the nanotubes with the mercury could be monitored while simultaneously recording the conductance. These measurements and observations confirm previously reported conductance quantization (Frank et al.: Science 280, 1744) of the nanotubes while providing additional details concerning the mercury nanotube contacts. We also report conductance versus voltage characteristics of carbon nanotubes.
Physical Review Applied, 2016
Nano electromechanical systems are considered as ultra sensitive devices for mass and force detec... more Nano electromechanical systems are considered as ultra sensitive devices for mass and force detection. Capacitive actuation is widely used in these devices but is known to degrade the quality factor of the resonator due to DC electrostatic damping. We report the enhancement of the quality factor of SiC vibrating nanowires detected nano optomechanically and electrically by applying an AC capacitive driving at a frequency above both the resonance frequency and the electrical cut-off frequency. Self-oscillations are demonstrated for optimal conditions. We developed an analytical model of the phenomenon and showed that it can lead to an improvement of the force sensitivity.
In-Situ Electric Transport of Carbon Nanotubes
Electron Microscopy of Nanotubes, 2003
Electrical transport in single-walled nanotubes (SWNTs) and multiwalled nanotubes (MWNTs) is of g... more Electrical transport in single-walled nanotubes (SWNTs) and multiwalled nanotubes (MWNTs) is of great importance for their applications in electronics [1]. The electronic band structure of SWNTs is well known: depending on the helicity and statistically in a third of the cases, a tube has two one-dimensional subbands (channels) that intercept the Fermi level, giving rise to metallic conduction. More precisely, only armchair tubes are gapless: all others are often referred to as metallic, although small gaps that are introduced by curvature effects of the order of 10 meV for 1.4 nm diameter SWNTs effect transport at low temperatures. The gap diminishes with increasing tube diameter. Measurements of nanotube conductance mainly use two techniques. Using lithographically made gold electrodes, a carbon nanotube is laid down across two or four electrodes, and the I-V characteristic is measured [2, 3]. The other technique takes the advantage of using liquid mercury as a soft contacting electrode; a nanotube is inserted into the mercury, and the conductance is monitored as a function of the depth that the nanotube is inserted into the mercury [4]. The latter has been carried out in-situ in TEM. This chapter is intended to review the progress in applying the second technique in electrical property characterization of nanotubes. A comprehensive review about all of the existing literature and the comparison of data in electrical characterization can be found from [5].
MRS Proceedings, 1999
Property characterization of nanomaterials is challenged by the small size of the structure becau... more Property characterization of nanomaterials is challenged by the small size of the structure because of the difficulties in manipulation. Here we demonstrate a novel approach that allows a direct measurement of the mechancial and electrical properties of individual nanotube-like structures by in-situ transmission electron microscopy (TEM). The technique is powerful in a way that it can directly correlate the atomic-scale microstructure of the carbon nanotube with its physical properties, providing an one-to-one correspondence in structure-property characterization. Applications of the technique will be demonstrated on mechanical properties, the electron field emission and the ballistic quantum conductance in individual nanotubes. A nanobalance technique is demonstrated that can be applied to measure the mass of a single tiny particle as light as 22 fg (1 f= 10−15).
2015 28th International Vacuum Nanoelectronics Conference (IVNC), 2015
Over these past years our team has been pioneering an original orientation which is the use of fi... more Over these past years our team has been pioneering an original orientation which is the use of field emission (FE) as a probe of mechanically resonating nanotubes (NTs), nanowires (NWs) and recently graphene. The resonators and electrical environment can be considered to be a nano-electro-mechanical system (NEMS). My goal here is to promote this subject better within the FE community whereas it has mostly been exposed within the NEMs community.
2012 International Conference on Electromagnetics in Advanced Applications, 2012
We present in this paper a study on highly resistive SiC nanowires in a singly clamped geometry. ... more We present in this paper a study on highly resistive SiC nanowires in a singly clamped geometry. We demonstrate that these field emission nanoelectromechanical systems (NEMS) can be synchronized ton an external AC signal and act as an amplifier.
Physical Review B, 2001
Phase transitions and staging in doped single-wall carbon nanotubes ͑SWNT's͒ are controversial is... more Phase transitions and staging in doped single-wall carbon nanotubes ͑SWNT's͒ are controversial issues. Here, we report on combined in situ conductivity and Raman measurements of Rb-doped SWNT's. Striking correlations between resistance, changes of resistance under laser irradiation, and frequency of the main Raman peak are observed. In the last steps of doping, two different Raman signatures, with peaks at 1596 and 1555 cm Ϫ1 , respectively, are observed and assigned to two different stable doped phases. The two phases coexist in a specific range of doping with the latter growing progressively at the expense of the former.
Quantum conductance and electron field emission of carbon nanotubes
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Papers by philippe poncharal