Magnetomotive instability and generation of mechanical vibrations in suspended semiconducting carbon nanotubes (original) (raw)
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Magnetic damping of a carbon nanotube nano-electromechanical resonator
New Journal of Physics, 2012
A suspended, doubly clamped single-wall carbon nanotube is characterized at cryogenic temperatures. We observe specific switching effects in dc-current spectroscopy of the embedded quantum dot. These have been identified previously as nano-electromechanical self-excitation of the system, where positive feedback from single-electron tunneling drives mechanical motion. A magnetic field suppresses this effect, by providing an additional damping mechanism. This is modeled by eddy current damping, and confirmed by measuring the resonance quality factor of the radio-frequency-driven nano-electromechanical resonator in an increasing magnetic field. Nano-electromechanical resonator systems offer an intriguing field of research, where both technical applications and fundamental insights into the limits of mechanical motion are possible. Among these systems, carbon nanotubes offer the ultimate electromechanical beam resonator [1-3], because of their stiffness, low mass and high aspect ratio. At the same time, they are an outstanding material for transport spectroscopy of quantum dots at cryogenic temperatures [4, 5]. Chemical vapor deposition (CVD) has been shown to produce on chip defect-free single-wall carbon nanotubes [6]. By performing this growth process as the last chip fabrication step, suspended defect-and contamination-free macromolecules can be integrated into electrode structures and characterized. On the electronic side, this has led to many valuable insights into, e.g., the physics of spatially confined few-carrier systems [7-9].
Magnetic effects on nonlinear mechanical properties of a suspended carbon nanotube
We propose a microscopic model for a nanoelectromechanical system made by a radio-frequency driven suspended carbon nanotube (CNT) in the presence of an external magnetic field perpendicular to the current. As a main result, we show that, when the device is driven far from equilibrium, one can tune the CNT mechanical properties by varying the external magnetic field. Indeed, the magnetic field affects the CNT bending mode dynamics inducing an enhanced damping as well as a noise term due to the electronic phase fluctuations. The quality factor, as observed experimentally, exhibits a quadratic dependence on external magnetic field strength. Finally, CNT resonance frequencies as a function of gate voltage acquire, increasing the magnetic field strength, a peculiar dip-peak structure that should be experimentally observed. arXiv:1212.0267v3 [cond-mat.mes-hall]
A tunable carbon nanotube electromechanical oscillator
Nature, 2004
Nanoelectromechanical systems (NEMs) hold promise for a number of scientific and technological applications. In particular, NEMs oscillators have been proposed for use in ultrasensitive mass detection, radio-frequency signal processing, and as a model system for exploring quantum phenomena in macroscopic systems. Perhaps the ultimate material for these applications is a carbon nanotube. They are the stiffest material known, have low density, ultrasmall cross-sections and can be defect-free. Equally important, a nanotube can act as a transistor and thus may be able to sense its own motion. In spite of this great promise, a room-temperature, self-detecting nanotube oscillator has not been realized, although some progress has been made. Here we report the electrical actuation and detection of the guitar-string-like oscillation modes of doubly clamped nanotube oscillators. We show that the resonance frequency can be widely tuned and that the devices can be used to transduce very small forces.
Nonlinear oscillations of a carbon nanotube resonator
2009 6th International Symposium on Mechatronics and its Applications, 2009
Nonlinear oscillations of a single-walled carbon nanotube excited harmonically near its primary resonance is considered. The carbon nanotube resonator is considered to be doubly-clamped at a source and a drain. The dynamic problem is modeled in the context of nonlinear vibration of an elastic beam theory, with mid-plane stretching. The response of the nanotube illustrates a sequence of period-doubling bifurcations leading to chaos. Introduction Due to their superior electronic, thermal and mechanical properties, carbon nanotubes are nowadays under significant focus to be modeled as promising NEMS building blocks for nanoelectronics, nanodevices, and nanocomposites [1]. Fundamental understanding the dynamic behavior of carbon nanotubes is crucial to their nanoelectromechanical emerging applications including oscillators, nano-scale clocks, parametric amplifiers, charge detection devices, and ultra-sensitive force sensors [2, 3]. In their recent review paper, Gibson et al. [4] devoted a full section to cover studies on the vibration of CNT nanoresonators. It is noted that only few publications have been oriented towards dealing with issues related to carbon nanotubes nonlinear vibrations, although evidences on geometric nonlinearities have been reported on a number of publications. In a relatively early study on the subject, Stumper and Noid [5] used a classical trajectory method to examine the coupled vibration of the 1 978-1-4244-3481-7/09/$25.00 [6] Postma, H. W. Ch., Kozinsky, I., Husain, A., and Roukes, M. L., "Dynamic range of nanotube-and nanowire-based electromechanical Systems,"
Journal of Micromechanics and Microengineering, 2011
We characterize the nanoelectromechanical response of suspended individual carbon nanotubes under high voltage biases. An abrupt upshift in the mechanical resonance frequency of approximately 3 MHz is observed at high bias. While several possible mechanisms are discussed, this upshift is attributed to the onset of optical phonon emission, which results in a sudden contraction of the nanotube due to its negative thermal expansion coefficient. This, in turn, causes an increase in the tension in the suspended nanotube, which upshifts its mechanical resonance frequency. This upshift is consistent with Raman spectral measurements, which show a sudden downshift of the optical phonon modes at high bias voltages. Using a simple model for oscillations on a string, we estimate the effective change in the length of the nanotube to be L/L ≈ −2 × 10 −5 at a bias voltage of 1 V.
Negative frequency tuning of a carbon nanotube nano-electromechanical resonator under tension
physica status solidi (b), 2013
A suspended, doubly clamped single wall carbon nanotube is characterized as driven nanoelectromechanical resonator at cryogenic temperatures. Electronically, the carbon nanotube displays small bandgap behaviour with Coulomb blockade oscillations in electron conduction and transparent contacts in hole conduction. We observe the driven mechanical resonance in dc-transport, including multiple higher harmonic responses. The data shows a distinct negative frequency tuning at finite applied gate voltage, enabling us to electrostatically decrease the resonance frequency to 75% of its maximum value. This is consistently explained via electrostatic softening of the mechanical mode.
physica status solidi (b), 2013
A suspended, doubly clamped single wall carbon nanotube is characterized as driven nanoelectromechanical resonator at cryogenic temperatures. Electronically, the carbon nanotube displays small bandgap behaviour with Coulomb blockade oscillations in electron conduction and transparent contacts in hole conduction. We observe the driven mechanical resonance in dc-transport, including multiple higher harmonic responses. The data shows a distinct negative frequency tuning at finite applied gate voltage, enabling us to electrostatically decrease the resonance frequency to 75% of its maximum value. This is consistently explained via electrostatic softening of the mechanical mode.
Carbon nanotubes as ultrahigh quality factor mechanical resonators
Nano letters, 2009
We have observed the transversal vibration mode of suspended carbon nanotubes at millikelvin temperatures by measuring the single-electron tunneling current. The suspended nanotubes are actuated contact-free by the radio frequency electric field of a nearby antenna; the mechanical resonance is detected in the time-averaged current through the nanotube. Sharp, gate-tuneable resonances due to the bending mode of the nanotube are observed, combining resonance frequencies of up to ν0 = 350 MHz with quality factors above Q = 10 5 , much higher than previously reported results on suspended carbon nanotube resonators. The measured magnitude and temperature dependence of the Q-factor shows a remarkable agreement with the intrinsic damping predicted for a suspended carbon nanotube. By adjusting the RF power on the antenna, we find that the nanotube resonator can easily be driven into the non-linear regime.
Journal of Applied Physics
With continuous downscaling of resonators, clamping is expected to significantly impact the mechanical stability as well as the energy dissipation mechanisms, especially at the nanoscale. To understand the clamping effects at the nanoscale, we here report on an experimental investigation of a same nanotube based resonator subjected to two different clamping configurations. We investigate clamping associated stability and damping mechanisms by pushing the resonator into the nonlinear regime. The nanotube was first dry-transferred and suspended between source-drain palladium electrodes resulting in a bottom clamped configuration. A selective top-metallization process by platinum atomic layer deposition applied later resulted in a top-bottom clamped configuration. Large nanotube motional amplitude leading to a nonlinear Duffing response initiated small slippage of the nanotube. This instability in clamping was seen in both clamping configurations and was measured as an irreversible resonance frequency downshift. For the measured resonator devices, a gate induced nanotube tension in the range of 58-71 pN was estimated to overcome clamping forces and initiate slipping. In terms of energy dissipation, the topmetallization process was accompanied by a reduction in amplitude dependent nonlinear damping and Q-factor enhancement. Subjecting the same nanotube to both clamping configurations allowed for a direct comparison of clamping and quantification of nonlinear damping. In the present case, nonlinear damping was observed at an estimated nanotube motional amplitude of 11 nm (and higher), being dominant in bottom clamped configuration, suggesting the origin of this nonlinear damping to partially stem from external mechanisms in addition to other possible internal dissipation paths reported such as viscoelastic effects.