| Posted: Aug 04, 2014 |
Unusual ultra-low-frequency fluctuations in freestanding graphene
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(Nanowerk News) Researchers from Shahid Rajayee Teacher Training University in association with foreign researchers succeeded in the measurement of thermal fluctuations created on the surface of graphene (see paper in Nature Communications: "Unusual ultra-low-frequency fluctuations in freestanding graphene").
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Graphene, being discovered about a decade ago by physicists from University of Manchester, has attracted the attention of many researchers in various sciences and engineering aspects due to its unique physical properties, including thermal and electrical conductivity, high density and mobility in charge carriers and optical and mechanical properties.
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By using scanning tunneling microscopic (STM) measurements taken from graphene surface, the researchers measured forced and free thermal fluctuations created in low frequency in graphene. The research was carried out by theoretical physicists from Shahid Rajayee Teacher Training University, University of Arkansas in the United States, University of Basel in Switzerland and University of Antwerp in Belgium.
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Dr. Mehdi Nik Amal, the supervisor of the research, explained about the results, and said, “The measurement was carried out on the surface of suspended graphene with an area of one square angstrom. Our observation shows that the force caused by the heat produced tunneling process and electrostatic force caused by bios voltage compete with each other during the control and change in fluctuations on graphene surface. Tunneling current acts on graphene surface in a way that causes thermal tension on the surface, the tension is opposed to other normal mechanical tensions due to graphene’s negative thermal extension coefficient at room temperature. This fact finally results in significant reduction in graphene’s fluctuation frequency.”
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