doi:10.1038/nindia.2011.183 Published online 22 December 2011
New research has shown that thin films of reduced graphene oxide and multilayer graphene nanoribbons could be used as high-speed nanosized photodetectors. They work as photodetectors in the presence of infrared laser beam.
Graphene — a one-atom-thick layer of carbon — has high electrical mobility and it absorbs light over a wide range of wavelengths. However, it is extremely difficult to produce high-quality graphene. In addition, graphene has no bandgap owing to the identical environments of the two carbon atoms in the graphene unit cell. Semiconductors and insulators with a non-zero bandgap allow electrons to move from the top of the valence band to the bottom of the conduction band when excited by heat or light. This generates electric current and helps make devices.
To design high-quality graphene materials with a bandgap, the researchers produced two different types of graphene material — reduced graphene oxide (RGO) films and six-layer graphene nanoribbons (GNRs).
The researchers measured the current–voltage characteristics of RGO and GNRs on a silicon dioxide substrate, both in dark and in the presence of infrared laser light. The electrical conductivities of both materials increased with rising laser intensity. Higher laser intensities provided more photons for absorption by the RGO and GNR films, thus resulting in a larger photocurrent.
For RGO, the current rose within 2 seconds after exposure to laser light. For GNRs, the current rose within 8 seconds of exposure. Both RGO and GNRs showed no performance degradation over a period of 3 months. The researchers say that RGO and GNRs can be used to design nanosized photoelectronic switches, which suggests that graphene may have a strong impact in nanoelectronics.
The authors of this work are from: Materials Research Centre, Indian Institute of Science and Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India.