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Model-independent quantitative measurement of nanomechanical oscillator vibrations using electron-microscope linescans

Wang, H; Fenton, JC; Chiatti, O; Warburton, PA; (2013) Model-independent quantitative measurement of nanomechanical oscillator vibrations using electron-microscope linescans. Review of Scientific Instruments , 84 (7) , Article 075002 . 10.1063/1.4811740. Green open access

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Abstract

Nanoscale mechanical resonators are highly sensitive devices and therefore, for application as highly sensitive mass balances, they are potentially superior to micromachined cantilevers. The absolute measurement of nanoscale displacements of such resonators remains a challenge, however, since the optical signal reflected from a cantilever whose dimensions are sub-wavelength is at best very weak. We describe a technique for quantitative analysis and fitting of scanning-electron microscope (SEM) linescans across a cantilever resonator, involving deconvolution from the vibrating resonator profile using the stationary resonator profile. This enables determination of the absolute amplitude of nanomechanical cantilever oscillations even when the oscillation amplitude is much smaller than the cantilever width. This technique is independent of any model of secondary-electron emission from the resonator and is therefore applicable to resonators with arbitrary geometry and material inhomogeneity. We demonstrate the technique using focussed-ion-beam–deposited tungsten cantilevers of radius ~60–170 nm inside a field-emission SEM, with excitation of the cantilever by a piezoelectric actuator allowing measurement of the full frequency response. Oscillation amplitudes approaching the size of the primary electron-beam can be resolved. We further show that the optimum electron-beam scan speed is determined by a compromise between deflection of the cantilever at low scan speeds and limited spatial resolution at high scan speeds. Our technique will be an important tool for use in precise characterization of nanomechanical resonator devices.

Type: Article
Title: Model-independent quantitative measurement of nanomechanical oscillator vibrations using electron-microscope linescans
Open access status: An open access version is available from UCL Discovery
DOI: 10.1063/1.4811740
Publisher version: http://dx.doi.org/10.1063/1.4811740
Language: English
Additional information: © 2013 Author(s). Published through AIP's Author Select initiative under the terms of the Creative Commons 3.0 Unported License.
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: http://discovery.ucl.ac.uk/id/eprint/1402573
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