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Here's a simple device. Stretch a sheet of graphene between two electrodes to form a kind of trampoline and then place a third electrode under the trampoline. Finally, send a DC current through the graphene and then add a radio frequency voltage on top to see what happens.

This is exactly the experiment that Yuehang Xu at Columbia University in New York and pals have done. They say the graphene sheet resonates when blasted with a voltage changing at radio frequency signals and that this can be easily measured by monitoring the capacitance between the sheet and the third electrode below the sheet.

That's a significant result. For some time now, physicists have been hoping to find ways of using nanoelectromechanical resonators to filter and generate radio signals directly. At present, this has to be done with various kinds of mixing techniques. The problem is that nanoelectromechanical devices all suffer from parasitic capacitance, which tends to drown out the signals that physicists are interested in at radio frequencies.

Xu and co say their graphene sheet device is immune from this because its design causes the effects of stray capacitance essentially to cancel out. And they prove it by using their device to pick out a radio frequency signal at 33.27 MHz.

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Category: Science