The successful fabrication of single layer graphene has greatly stimulated the progress of the research on graphene. In this article, focusing on the basic electronic and transport properties of graphene nanoribbons (GNRs), we review the recent progress of experimental fabrication of GNRs, and the theoretical and experimental investigations of physical properties and device applications of GNRs. We also briefly discuss the research efforts on the spin polarization of GNRs in relation to the edge states.
Experimental Fabrication of Graphene Nanoribbons
* graphene can be patterned by traditional e-beam lithography technique into nanoribbons with various widths ranging from 20 to 500nm
* 10-nm-wide nanoribbon has been etched via scanning tunnelling microscope (STM) lithography.
* chemically derived GNRs with various widths ranging from 50 nm to sub-10 nm. These GNRs have atomic-scale ultrasmooth edges
Electronic and Transport Properties
* GNRs with armchair-shaped edges can be either metallic or semiconducting depending on their widths
* GNRs with zigzag-shaped edges are metallic with peculiar edge states on both sides of ribbons regardless of their widths
* all of the AGNRs exhibit semiconducting behavior and the energy gaps decrease as a function of increasing ribbon widths.
Edge Disorder in Graphene Nanoribbons
Current experimental techniques (such as lithography) are not able to realize exact control of the edge structures of GNRs and the edges are always very rough due to the limitation of the fabrication technology. There are theoretical evidences that such edge disorders can significantly change the electronic properties of GNRs, and lead to some unexpected physics effect, such as the Anderson localization and Coulomb blockade effect
Transistors Based on Graphene Nanoribbons
Without atomically precise edge control during fabrication, it is hard to get reliable and stable performance of GNRFETs. Due to their unusual basic properties, GNRs as well as graphene are promising for a large number of applications, from spin filters, valley filters, to chemical sensors. GNRs can be chemically and/or structurally modified in order to change its functionality and hence its potential applications.
Due to the interesting electronic and magnetic properties, GNRs have been demonstrated as a promising candidate material for future post-silicon electronics such as transport materials, field effect transistors, and spin injection or filter. More experimental efforts will focus on fabricating high quality nanoribbon samples with accurate control of the edge structures.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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