S. T. Purcell

Claude Bernard University Lyon 1, Villeurbanne, Rhône-Alpes, France

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Publications (67)288.56 Total impact

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    ABSTRACT: We demonstrate field evaporation of insulating materials, specifically BN nanotubes and undoped Si nanowires, assisted by a convergent electron beam. Electron irradiation leads to positive charging at the nano-object's apex and to an important increase of the local electric field thus inducing field evaporation. Experiments performed both in a transmission electron microscope and in a scanning electron microscope are presented. This technique permits the selective evaporation of individual nanowires in complex materials. Electron assisted field evaporation could be an interesting alternative or complementary to laser induced field desorption used in atom probe tomography of insulating materials.
    Applied Physics Letters 05/2015; 106(19):193102. DOI:10.1063/1.4921166 · 3.52 Impact Factor
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    ABSTRACT: Synchronization has been reported for a wide range of self-oscillating systems. However, even though it has been predicted theoretically for several decades, the experimental realization of phase self-oscillation, sometimes called phase trapping, in the high driving regime has been studied only recently. We explored in detail the phase dynamics in a synchronized field emission SiC nanoelectromechanical system with intrinsic feedback. A richer variety of phase behavior has been unambiguously identified, implying phase modulation and inertia. This synchronization regime is expected to have implications for the comprehension of the dynamics of interacting self-oscillating networks and for the generation of frequency modulated signals at the nanoscale.
    New Journal of Physics 08/2014; 16(8):083009. DOI:10.1088/1367-2630/16/8/083009 · 3.67 Impact Factor
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    ABSTRACT: We report ultra-low threshold optically induced self-oscillations of a ultra-low dissipation nanowire. We interpret the asymmetrically observed responses as a signature of the laser shot noise drive, consistent with our system’s parameters
    CLEO: QELS_Fundamental Science; 06/2014
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    ABSTRACT: We present here well-defined Coulomb staircases using an original field-emission experiment on several individual in situ-grown single-wall carbon nanotubes. A unique in situ process was applied nine times to progressively shorten one single-wall carbon nanotube down to ≃10 nm, which increased the oscillations periods from 5.5 to 80 V, the temperature for observable Coulomb staircase to 1100 K and the currents to 1.8 μA. This process led to the brightest electron source ever reported [9×1011 A/(str m2 V)].
    Physical Review Letters 03/2014; 112(12):126805. DOI:10.1103/PhysRevLett.112.126805 · 7.73 Impact Factor
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    ABSTRACT: A theoretical and experimental description of the threshold, amplitude, and stability of a self-oscillating nanowire in a field emission configuration is presented. Two thresholds for the onset of self-oscillation are identified, one induced by fluctuations of the electromagnetic environment and a second revealed by these fluctuations by measuring the probability density function of the current. The ac and dc components of the current and the phase stability are quantified. An ac to dc ratio above 100% and an Allan deviation of 1.3x10-5 at room temperature can be attained. Finally, it is shown that a simple nonlinear model cannot describe the equilibrium effective potential in the self-oscillating regime due to the high amplitude of oscillations.
    Physical Review B 12/2013; 88(19). DOI:10.1103/PhysRevB.88.195428 · 3.66 Impact Factor
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    ABSTRACT: We report here the first realization of top-down silicon nanowires (SiNW) transduced by both junction-less field-effect transistor (FET) and the piezoresistive (PZR) effect. The suspended SiNWs are among the smallest top-down SiNWs reported to date, featuring widths down to ∼20 nm. This has been achieved thanks to a 200 mm-wafer-scale, VLSI process fully amenable to monolithic CMOS co-integration. Thanks to the very small dimensions, the conductance of the silicon nanowire can be controlled by a nearby electrostatic gate. Both the junction-less FET and the previously demonstrated PZR transduction have been performed with the same SiNW. These self-transducing schemes have shown similar signal-to-background ratios, and the PZR transduction has exhibited a relatively higher output signal. Allan deviation (σA) of the same SiNW has been measured with both schemes, and we obtain σA ∼ 20 ppm for the FET detection and σA ∼ 3 ppm for the PZR detection at room temperature and low pressure. Orders of magnitude improvements are expected from tighter electrostatic control via changes in geometry and doping level, as well as from CMOS integration. The compact, simple topology of these elementary SiNW resonators opens up new paths towards ultra-dense arrays for gas and mass sensing, time keeping or logic switching systems on the SiNW-CMOS platform.
    Nanotechnology 11/2013; 24(43):435203. DOI:10.1088/0957-4484/24/43/435203 · 3.67 Impact Factor
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    ABSTRACT: We report here the observation of a new self-oscillation mechanism in nanoelectromechanical systems (NEMS). A highly resistive nanowire was positioned to form a point-contact at a chosen vibration node of a silicon carbide nanowire resonator. Spontaneous and robust mechanical oscillations arise when a sufficient DC voltage is applied between the two nanowires. An original model predicting the threshold voltage is used to estimate the piezoresistivity of the point contact in agreement with the observations. The measured input power is in the pW-range which is the lowest reported value for such systems. The simplicity of the contacting procedure and the low-power consumption open a new route for integrable and low-loss self-excited NEMS devices.
    Nano Letters 03/2013; 13(4). DOI:10.1021/nl304352w · 12.94 Impact Factor
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    ABSTRACT: New models of fluid transport are expected to emerge from the confinement of liquids at the nanoscale, with potential applications in ultrafiltration, desalination and energy conversion. Nevertheless, advancing our fundamental understanding of fluid transport on the smallest scales requires mass and ion dynamics to be ultimately characterized across an individual channel to avoid averaging over many pores. A major challenge for nanofluidics thus lies in building distinct and well-controlled nanochannels, amenable to the systematic exploration of their properties. Here we describe the fabrication and use of a hierarchical nanofluidic device made of a boron nitride nanotube that pierces an ultrathin membrane and connects two fluid reservoirs. Such a transmembrane geometry allows the detailed study of fluidic transport through a single nanotube under diverse forces, including electric fields, pressure drops and chemical gradients. Using this device, we discover very large, osmotically induced electric currents generated by salinity gradients, exceeding by two orders of magnitude their pressure-driven counterpart. We show that this result originates in the anomalously high surface charge carried by the nanotube's internal surface in water at large pH, which we independently quantify in conductance measurements. The nano-assembly route using nanostructures as building blocks opens the way to studying fluid, ionic and molecule transport on the nanoscale, and may lead to biomimetic functionalities. Our results furthermore suggest that boron nitride nanotubes could be used as membranes for osmotic power harvesting under salinity gradients.
    Nature 02/2013; 494(7438):455-8. DOI:10.1038/nature11876 · 42.35 Impact Factor
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    ABSTRACT: This paper explores the field emission (FE) properties of highly crystalline Si nanowires (NWs) with controlled surface passivation. The NWs were batch-grown by the vapor-liquid-solid process using Au catalysts with no intentional doping. The FE current-voltage characteristics showed quasi-ideal current saturation that resembles those predicted by the basic theory for emission from semiconductors, even at room temperature. In the saturation region, the currents were extremely sensitive to temperature and also increased linearly with voltage drop along the nanowire. The latter permits the estimation of the doping concentration and the carrier lifetime, which is limited by surface recombination. The conductivity could be tuned over 2 orders of magnitude by in situ hydrogen passivation/desorption cycles. This work highlights the role of dangling bonds in surface leakage currents and demonstrates the use of hydrogen passivation for optimizing the FE characteristics of Si NWs.
    ACS Nano 07/2012; 6(8):7463-71. DOI:10.1021/nn302744e · 12.03 Impact Factor
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    ABSTRACT: This article presents a study of the poorly understood "shear-force" used in an important class of near-field instruments that use mechanical resonance feedback detection. In the case of a metallic probe near a metallic surface in vacuum, we show that in the 10-60 nm range there is no such a thing as a shear-force in the sense of the nonconservative friction force. Fluctuations of the oscillator resonance frequency, likely induced by local charge variations, could account for the reported effects in the literature without introducing a dissipative force.
    Nano Letters 06/2012; 12(7):3551-6. DOI:10.1021/nl301618p · 12.94 Impact Factor
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    ABSTRACT: In this article, we explore and compare two distinct configurations of the “nanoradio” concept where individual carbon nanotube resonators are the central electromechanical element permitting signal demodulation. The two configurations of singly-clamped field emitters and doubly-clamped field effect transistors are examined which at first glance are quite different, but in fact involve quite similar physical concepts. Amplitude, frequency and digital demodulation are demonstrated and the analytical formulae describing the demodulation are derived as functions of the system parameters. The crucial role played by the mechanical resonance in demodulation is clearly demonstrated. For the field emission configuration we particularly concentrate on how the demodulation depends on the variation of the field amplification factor during resonance and show that amplitude demodulation results in the best transmitted signal. For the transistor configuration the important aspect is the variation of the nanotube conductance as a function of its distance to the gate. In this case frequency demodulation is much more effective and digital signal processing was achieved. The respective strengths and weaknesses of each configuration are discussed throughout the article.RésuméDans cet article nous analysons et comparons deux configurations différentes du concept de « nanoradio » où des nanotubes de carbone individuels résonant constituent lʼélément électro-mécanique essentiel permettant la démodulation du signal radio. Les deux configurations, émetteur de champ simplement encastré et transistor à effet de champ doublement encastré, peuvent à première vue sembler relativement différentes mais, après analyse, elles reposent sur des concepts physiques similaires. La démodulation de signaux codés en amplitude (AM), fréquence (FM) et phase (PM) est démontrée et les formules analytiques décrivant cette démodulation sont exprimées en fonction des paramètres des systèmes. Le rôle crucial joué par la résonance mécanique dans le processus de démodulation est ainsi clairement mis en évidence. Pour la configuration en émission de champ nous montrons comment la démodulation dépend de la variation du facteur dʼamplification de champ durant la résonance et que les meilleures performances sont obtenues pour la démodulation dʼun signal codé en amplitude. Pour la configuration transistor le point principal est la variation de la conductance du nanotube en fonction de sa distance à la grille. Dans ce cas la démodulation dʼun signal codé en fréquence est plus efficace et la démodulation de signaux digitaux a été démontré. Les avantages et défauts de chaque configuration sont discutés tout au long de lʼarticle.
    Comptes Rendus Physique 06/2012; 13(5):395–409. DOI:10.1016/j.crhy.2012.01.003 · 1.64 Impact Factor
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    ABSTRACT: We study the contribution of ohmic dissipation to the mechanical damping of nanoresonators. This damping occurs when DC voltage is applied to a resistive resonator, because the mechanical motion modifies the associated capacitance, thus inducing a dissipative current. Silicon carbide nanowire resonators were studied as a function of applied voltage and their geometrical environment. Nanometric positioners were used to control and continuously modify the position of the resonator with respect to counter electrodes. The experimental results are shown to be in agreement with an electromechanical model developed here, which allows for the establishment of a universal formula for the lower dissipation limit of a nanoresonator in its capacitive environment.
    Physical review. B, Condensed matter 02/2012; 85(7). DOI:10.1103/PhysRevB.85.075407 · 3.66 Impact Factor
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    ABSTRACT: 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.
    Electromagnetics in Advanced Applications (ICEAA), 2012 International Conference on; 01/2012
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    ABSTRACT: Silicon Nanowires (SiNWs) are being studied for a wide variety of applications in nanoscience with significant progress in their integration into devices such as transistors, solar cells, photodectors, chemical sensors, etc.. However there has been much less work on field emission (FE) even though their semiconducting properties open distinct possibilities compared to metallic emitters and carbon nanotubes. The few measurements in the literature for SiNW arrays have only shown linear Fowler-Nordheim (FN) behavior as for metallic emitters. In addition to strong current saturation in FE due to the band-gap, their properties could be strongly influenced by surface states because of their large surface-to-volume ratio. As a consequence, there is a clear need for in-depth FE studies of individual NWs in order to understand surface effects and optimize FE characteristics.
    Vacuum Nanoelectronics Conference (IVNC), 2012 25th International; 01/2012
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    ABSTRACT: The authors present studies on the field emission (FE) mechanism and the FE-induced transformation of individual anatase TiO2 nanowires (NWs). The NWs were synthesized by electrospinning followed by calcination at 500 °C which produces polycrystalline anatase nanofibers as determined by Raman spectroscopy and transmission electron microscopy (TEM) characterization. Nanowires of ∼100 nm in diameter were individually mounted at the apexes of tungsten tips for further physical characterization. The FE experiments were carried out in a TEM which allows the measurement of the FE current while simultaneously observing structural modifications leading to the NW’s destruction. For low currents (below 100 nA), we observe reproducible FE Fowler-Nordheim I/V characteristics. Higher currents (up to 1 μA) can be obtained but sudden destruction of the NW may take place. Our observations show that a thermally-activated transition occurs and leads to rapid re-crystallization phenomena and a variation of the FE characteristics. If not controlled, this transition leads to thermal runaway and sample destruction. The understanding of the destruction phenomena is a key parameter to further improve the FE performance of such nanowire cathodes.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2012; 30(1):1801-. DOI:10.1116/1.3668121 · 1.36 Impact Factor
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    ABSTRACT: We have recently shown that individual single wall carbon nanotubes (CNTs) can be grown on metallic tips in a field emission microscope (FEM) on which carbon passivation layers and Ni catalysts have been pre-deposited in situ (see Fig. 1). This allows direct observation from the nucleation stage until the end of the growth [1]. In this talk I will review this unique synthesis method and our more recent progress, and discuss the comportment of the as-grown CNTs as field emission sources and nano-mechanical oscillators.
    Vacuum Nanoelectronics Conference (IVNC), 2012 25th International; 01/2012
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    ABSTRACT: High frequency Silicon NanoWire Resonators (SNWR) have been fabricated and their performances for time reference applications have been assessed. The SNWR have been designed to operate at different frequencies going from 55 MHz up to 300 MHz with quality factors higher than 2000 at room temperature under high vacuum. The measured temperature coefficient of frequency (TCF) for different SNWR is about 40 ppm over a range of temperature going from 4 K to 300 K. The evolution of the quality factor as function of temperature has also been measured as well as the Allan deviation for different nanowire lengths.
    Frequency Control Symposium (FCS), 2012 IEEE International; 01/2012
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    ABSTRACT: The fabrication and the electromechanical characterization of top-down silicon nanowire resonators for sensing applications are presented. To date, these are the smallest nanowires reported that can take advantage of compatibility with CMOS fabrication and co-integration. The nanowires are actuated through the electrostatic force and the resonances are transduced by the piezoresistive effect of second order. Their electromechanical characterization is performed with the FM demodulation technique, which has allowed the detection of resonances at frequencies as high as 94.7 MHz. In the future, silicon nanowires could serve as mass sensors with sensitivities as low as 1zg/root Hz. (C) 2011 Published by Elsevier Ltd.
    Procedia Engineering 12/2011; 25:1649-1652. DOI:10.1016/j.proeng.2011.12.408
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    ABSTRACT: Measurements of the gauge factor of suspended, top-down silicon nanowires are presented. The nanowires are fabricated with a CMOS compatible process and with doping concentrations ranging from 2 × 10(20) down to 5 × 10(17) cm(-3). The extracted gauge factors are compared with results on identical non-suspended nanowires and with state-of-the-art results. An increase of the gauge factor after suspension is demonstrated. For the low doped nanowires a value of 235 is measured. Particular attention was paid throughout the experiments to distinguishing real resistance change due to strain modulation from resistance fluctuations due to charge trapping. Furthermore, a numerical model correlating surface charge density with the gauge factor is presented. Comparison of the simulations with experimental measurements shows the validity of this approach. These results contribute to a deeper understanding of the piezoresistive effect in Si nanowires.
    Nanotechnology 09/2011; 22(39):395701. DOI:10.1088/0957-4484/22/39/395701 · 3.67 Impact Factor
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    ABSTRACT: A simple technique is explored to determine the temporal photo-response, Τ, of individual semiconducting SiC and Si nanowires (NWs), with a high time resolution. Laser-assisted field emission (LAFE) from the NWs is first shown to be highly sensitive to continuous laser illumination. Pulsed illumination is then combined with measurements of the total energy distributions to determine Τ which were rather large, 4–200 μs. The time response scaled roughly with the square of the NWs length and could be attributed to laser-induced heating. LAFE is thus a new tool for quantifying rapid thermo-optical effects in such nano-objects.
    Applied Physics Letters 08/2011; 99. DOI:10.1063/1.3627168 · 3.52 Impact Factor

Publication Stats

1k Citations
288.56 Total Impact Points

Institutions

  • 1992–2014
    • Claude Bernard University Lyon 1
      • • Laboratoire de physique de la matière condensée et nanostructures (LPMCN)
      • • Laboratoire de la matière condensée et nanostructures (LPMCN)
      • • Laboratoire de la physique de la matière condensée et nanostructures (PMCN)
      Villeurbanne, Rhône-Alpes, France
  • 2001–2012
    • French National Centre for Scientific Research
      • Laboratoire des Multimatériaux et Interfaces (LMI)
      Lutetia Parisorum, Île-de-France, France
  • 2007–2009
    • University of Lyon
      Lyons, Rhône-Alpes, France
  • 1994
    • Universidad Autónoma de Madrid
      Madrid, Madrid, Spain