Abstract
Graphene can be transformed from a semimetal into a semiconductor if it is confined into nanoribbons narrower than 10 nm with controlled crystallographic orientation and well-defined armchair edges. However, the scalable synthesis of nanoribbons with this precision directly on insulating or semiconducting substrates has not been possible. Here we demonstrate the synthesis of graphene nanoribbons on Ge(001) via chemical vapour deposition. The nanoribbons are self-aligning 3° from the Ge〈110〉 directions, are self-defining with predominantly smooth armchair edges, and have tunable width to <10 nm and aspect ratio to >70. In order to realize highly anisotropic ribbons, it is critical to operate in a regime in which the growth rate in the width direction is especially slow, <5 nm h−1. This directional and anisotropic growth enables nanoribbon fabrication directly on conventional semiconductor wafer platforms and, therefore, promises to allow the integration of nanoribbons into future hybrid integrated circuits.
Highlights
Graphene can be transformed from a semimetal into a semiconductor if it is confined into nanoribbons narrower than 10 nm with controlled crystallographic orientation and welldefined armchair edges
Scalable nanoribbon fabrication has been reported via epitaxial growth on templated SiC nanofacets[22] and by chemical vapour deposition (CVD) on surface features, such as steps[23], twins[24] and trenches[25], as well as on patterned catalysts in which growth is confined to predetermined areas that define the ribbon dimensions[26,27,28,29]
While as high as 90% of the graphene crystals that nucleate evolve as ribbons, more compact graphene crystals with lower aspect ratio and edges that are not aligned along Geh110i directions are observed
Summary
Graphene can be transformed from a semimetal into a semiconductor if it is confined into nanoribbons narrower than 10 nm with controlled crystallographic orientation and welldefined armchair edges. We show that the CVD of graphene on Ge(001) can be controlled to yield oriented nanoribbons with sub-10 nm width and smooth armchair edges.
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