Nanoribbons

Abstract

Graphene nanoribbons have intriguing electronic structures, which are large edge geometry dependent. Armchair-edged graphene nanoribbons, which are energetically stable, have a ribbon-width-dependent intrinsic energy gap, while zigzag-edged ones have spin-polarized nonbonding edge states in the vicinity of the edge region. The edge state is the origin of electronic, magnetic and chemical activities. These features of the electronic structures can be characterized using microprobe techniques such as scanning tunneling microscopy/spectroscopy (STMscanningtunneling microscopy (STM)/STSscanningtunneling spectroscopy (STS)), atomic force microscopy (AFMatomic force microscopy (AFM)), transmission electron microscopy (TEMtransmission electron microscopy (TEM)), Raman spectroscopy, x-ray absorption, angle-resolved photoemission spectroscopy, electron transport, and magnetic measurements. Graphene nanostructures are synthesized using top-down and bottom-up methods, in the latter of which graphene nanostructures with atomically precise edges can be created. The presence of bandgap, which varies depending on the ribbon width and the edge geometry, makes graphene an important candidate for electronics device applications. The spin-polarized edge states localized in the vicinity of edges in zigzag-edged nanoribbons are expected to be utilized for spintronics applications.