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Shot noise in ballistic graphene.
1Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland. r.danneau@boojum.hut.fi
Physical Review Letters
|June 4, 2008
Summary
We studied shot noise in graphene devices, finding the Fano factor peaks at the Dirac point for wide samples. This noise level decreases with higher charge density, aligning with theories on graphene
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Shot noise is a fundamental property of electronic transport.
- Graphene exhibits unique electronic properties, especially near its Dirac point.
- Understanding noise in graphene field-effect devices is crucial for electronic applications.
Purpose of the Study:
- Investigate shot noise in graphene field-effect devices.
- Characterize the Fano factor's dependence on device geometry and charge density.
- Compare experimental results with theoretical predictions for transport mechanisms.
Main Methods:
- Fabrication of graphene field-effect devices with varying width-to-length ratios (W/L).
- Measurement of shot noise in the temperature range of 4.2-30 K at low frequencies (600-850 MHz).
- Analysis of the Fano factor (F) as a function of charge density and device geometry.
Main Results:
- For large W/L ratios, the Fano factor (F) reaches a maximum of approximately 1/3 at the Dirac point.
- The Fano factor significantly decreases with increasing charge density for wide samples.
- Smaller W/L ratios result in a substantially lower Fano factor at the Dirac point.
Conclusions:
- Experimental findings are consistent with theoretical models of transport in clean graphene.
- Evanescent electronic states are identified as the dominant transport mechanism at the Dirac point.
- Device geometry plays a critical role in determining shot noise characteristics in graphene.
