Measurement of mechanical resonance and losses in nanometer scale silicon wires

Carr, Dustin W.; Evoy, Stéphane; Šekarić, L.; Craighead, Harold G.; Parpia, J. M.

doi:10.1063/1.124554

Cited by 296 publications

(223 citation statements)

References 15 publications

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“…The minimum resolvable signal is achieved at 0.1 mV drive and about 5 A sensing current. Hence, at the highest possible current of 20 A, we can detect a resonance at x c /450/4ϭ0.03 Å, or 3 ϫ10 Ϫ3 Å/ͱHz, which is consistent with our estimate based on Johnson noise from beam resistance at 4.2 K. The corresponding force sensitivity is 75 fN/ͱHz, comparable with previous schemes to detect small NEMS resonators by optical interferometry 6 and the magnetomotive method. 7 The required force to drive the beam to the nonlinearity threshold is 1.5 nN.…”

supporting

confidence: 79%

Two-dimensional electron-gas actuation and transduction for GaAs nanoelectromechanical systems

Tang

Huang

Roukes

et al. 2002

Applied Physics Letters

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We have fabricated doubly clamped beams from GaAs/AlGaAs quantum-well heterostructures containing a high-mobility two-dimensional electron gas ͑2DEG͒. Applying an rf drive to in-plane side gates excites the beam's mechanical resonance through a dipole-dipole mechanism. Sensitive high-frequency displacement transduction is achieved by measuring the ac emf developed across the 2DEG in the presence of a constant dc sense current. The high mobility of the incorporated 2DEG provides low-noise, low-power, and high-gain electromechanical displacement sensing through combined piezoelectric and piezoresistive mechanisms. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1516237͔ Thin, suspended two-dimensional electron gas ͑2DEG͒ heterostructures have been recently perfected, and have subsequently been employed for nanoscale conducting devices. 1,2 In this letter, we present a high-resolution displacement readout that is based upon our ability to achieve very high mobility suspended quantum wires. Molecular beam epitaxial ͑MBE͒ grown materials are directly patterned and in-plane gates are used to excite the vibration. No metallization is needed, hence high Q values can be obtained.The starting material was a specially designed, MBEgrown, 2DEG heterostructure similar to that used in Ref. 1. The structural layer stack comprises seven individual layers having a total thickness of 115 nm. The top and bottom are thin GaAs cap layers preventing oxidation of the Al 0.3 Ga 0.7 As:Si donor layers in between. The central 10-nmthick GaAs layer forms a quantum well sustaining a high mobility 2DEG located 37 nm below the top surface and surrounded by two AlGaAs spacer layers. Below the structural layer stack is a 400 nm Al 0.8 Ga 0.2 As sacrificial layer. The structure was intentionally made asymmetric to avoid neutralizing the piezoelectric effect of GaAs.After ohmic contacts were deposited, a thick layer of poly-methyl-methacrylate ͑PMMA͒ is spun on the chip, followed by a single electron-beam lithography step to expose trenches in PMMA that isolate the beam from its side gates. PMMA was then employed as a direct mask against a low voltage electron cyclotron reactor etch performed to further etch the trenches to the sacrificial layer. After stripping off the PMMA, final structure relief is achieved by removing the sacrificial layer beneath the beams with diluted HF. To minimize the damage to the 2DEG from dry etching, a Cl 2 /He plasma was chosen because of its excellent etching characteristics, such as smooth surface morphology and vertical sidewall. A stable etching speed at 35Å /s is obtained under conditions of less than 150 V self-bias ͑20 W constant rf power͒, Cl 2 and He flow rate ratio 1:9, 3 mTorr pressure, and 300 W microwave power. With the same method, we have also fabricated suspended Hall bars and extensively characterized the resulting suspended 2DEG. Before processing, the initial mobility and density after illumination are 5.1 ϫ10 5 cm 2 /Vs, 1.26ϫ10 12 cm Ϫ2 , respectively. With our improved low damage etching...

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supporting

confidence: 79%

Two-dimensional electron-gas actuation and transduction for GaAs nanoelectromechanical systems

Tang

Huang

Roukes

et al. 2002

Applied Physics Letters

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“…Previous studies, which have largely been analytical, have been restricted to certain limiting cases of these parameters. Recently work on oscillating nanoscale systems, such as carbon nanotubes [4] and silicon nanowires [5], has opened the possibility of experimentally exploring such vibrations in entirely new regimes. In the present work, we study numerically the oscillations of a one dimensional elastic system over an extensive range of both the slack and force parameters, providing insight into the physics which separates this parameter space into three distinct regimes of behavior.…”

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confidence: 99%

Modeling a Suspended Nanotube Oscillator

2005

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We present a general study of oscillations in suspended one-dimensional elastic systems clamped at each end, exploring a wide range of slack (excess length) and downward external forces. Our results apply directly to recent experiments in nanotube and silicon nanowire oscillators. We find the behavior to simplify in three well-defined regimes which we present in a dimensionless phase diagram. The frequencies of vibration of such systems are found to be extremely sensitive to slack.Vibrations of one-dimensional systems (i.e. systems with cross-sectional dimension much smaller than their length) suspended under the influence of a downward force have long been of interest in the context of such applications as beams, cables supporting suspension bridges and ship moorings [1,2,3]. Such systems display a wide range of behavior, depending on the amount of slack present in the system, the downward force, and the aspect ratio. Previous studies, which have largely been analytical, have been restricted to certain limiting cases of these parameters. Recently work on oscillating nanoscale systems, such as carbon nanotubes [4] and silicon nanowires [5], has opened the possibility of experimentally exploring such vibrations in entirely new regimes. In the present work, we study numerically the oscillations of a one dimensional elastic system over an extensive range of both the slack and force parameters, providing insight into the physics which separates this parameter space into three distinct regimes of behavior.The treatment below is entirely general with illustrative examples taken from parameters relevant to carbon nanotubes. Since their discovery in 1991 [6], nanotubes have found many applications in device technology due to their small size, robust structure and superior elastic properties [7,8,9,10]. Many of these applications involve the use of nanotubes as mechanical oscillators, making theoretical understanding of the vibrational properties of nanotubes in various geometries of current interest [4,11]. Recent experiments [12] have studied the behavior of the transverse vibrations of a suspended nanotube clamped at both ends, under the action of a downward force, as sketched in Figure 1. These suspended nanotubes generally have around 1% slack, denoted in this work by s, which we define to be the ratio of the excess length of the tube to the distance between clamping points.Analytic model and computational techniques -The potential energy of a one-dimensional elastic continuum under a uniform downward force isHere, l represents distance along the system of unstretched length L; u(l), R(l) and z(l) represent the local strain, radius of curvature and vertical displacement, 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000111 111 respectively; E and F are the extensional and flexural rigidities; and f is the downward force per unit length. For single-walled nanotubes with diamet...

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“…7 were done at different temperatures. [62][63][64][65][66][67][68]3,2,69 Given what is known from electronic and photonic device physics regarding oxidation and reconstruction of the Si surface, it seems clear that the mechanical properties of the smallest NEMS devices will deviate greatly from those in bulk. It may prove quite difficult to achieve ultrahigh Q with such extreme surface-to-volume ratios, if only conventional patterning approaches are utilized.…”

Section: Principal Challenges a Pursuit Of Ultrahigh Qmentioning

confidence: 99%

Nanoelectromechanical Systems

Roukes¹

2005

Microsystems

100

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Nanoelectromechanical systems ͑NEMS͒ are drawing interest from both technical and scientific communities. These are electromechanical systems, much like microelectromechanical systems, mostly operated in their resonant modes with dimensions in the deep submicron. In this size regime, they come with extremely high fundamental resonance frequencies, diminished active masses, and tolerable force constants; the quality ͑Q͒ factors of resonance are in the range Q ϳ 10 3 -10 5 -significantly higher than those of electrical resonant circuits. These attributes collectively make NEMS suitable for a multitude of technological applications such as ultrafast sensors, actuators, and signal processing components. Experimentally, NEMS are expected to open up investigations of phonon mediated mechanical processes and of the quantum behavior of mesoscopic mechanical systems. However, there still exist fundamental and technological challenges to NEMS optimization. In this review we shall provide a balanced introduction to NEMS by discussing the prospects and challenges in this rapidly developing field and outline an exciting emerging application, nanoelectromechanical mass detection.

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Measurement of mechanical resonance and losses in nanometer scale silicon wires

Cited by 296 publications

References 15 publications

Two-dimensional electron-gas actuation and transduction for GaAs nanoelectromechanical systems

Two-dimensional electron-gas actuation and transduction for GaAs nanoelectromechanical systems

Modeling a Suspended Nanotube Oscillator

Nanoelectromechanical Systems

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