Unusual ultra-low-frequency fluctuations in freestanding graphene.
Intrinsic ripples in freestanding graphene have been exceedingly difficult to study. Individual ripple geometry was recently imaged using scanning tunnelling microscopy, but these measurements are limited to static configurations. Thermally-activated flexural phonon modes should generate dynamic changes in curvature. Here we show how to track the vertical movement of a one-square-angstrom region of freestanding graphene using scanning tunnelling microscopy, thereby allowing measurement of the out-of-plane time trajectory and fluctuations over long time periods. We also present a model from elasticity theory to explain the very-low-frequency oscillations. Unexpectedly, we sometimes detect a sudden colossal jump, which we interpret as due to mirror buckling. This innovative technique provides a much needed atomic-scale probe for the time-dependent behaviours of intrinsic ripples. The discovery of this novel progenitor represents a fundamental advance in the use of scanning tunnelling microscopy, which together with the application of a thermal load provides a low-frequency nano-resonator.
Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA.
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Xu
1] Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, Antwerpen B-2020, Belgium [2] Department of Physics, Shahid Rajaee Teacher Training University, Lavizan, Tehran 16788, Iran.
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Neek-Amal
Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA.
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Barber
Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA.
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Schoelz
Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA.
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Ackerman
Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA.
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Thibado
Departement Physik, Universat Basel, Klingelbergstrasse 82, Basel CH-4056, Switzerland.
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Sadeghi
Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, Antwerpen B-2020, Belgium.
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Peeters
D004548:Elasticity; D006108:Graphite / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling / Q000379:methods*; D008956:Models, Chemical; D036103:Nanotechnology / Q000379:methods*; D060739:Phonons; D013696:Temperature
D006108:Graphite