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Your search keyword '"Amadeo L Vazquez de Parga"' showing total 3 results
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3 results on '"Amadeo L Vazquez de Parga"'

1. (Invited) Site-Selective Covalent Patterning of Epitaxial Graphene with Periodicity at the Nanometer Scale

Author

Rodolfo Miranda, Emilio M Perez, Fabian Calleja, Juan Jesus Navarro, and Amadeo L. Vazquez de Parga

Abstract

The covalent functionalization of graphene with long-range periodicity is highly desirable to provide control over its electronic, optical, or magnetic properties. We describe a method for the site-selective, covalent modification of graphene with strict spatial periodicity at the nanometer scale. The periodic landscape is provided by a single monolayer of graphene epitaxially grown on Ru(0001), that presents a moiré pattern with 3 nm periodicity due to the mismatch between the carbon and ruthenium hexagonal lattices. The moiré contains periodically arranged sites where the charge transfer from the metallic substrate is enhanced as a result of the local graphene-ruthenium interaction and, as a consequence, these sites show higher chemical reactivity. This is illustrated by imaging with STM under UHV conditions the attachment of cyanomethyl radicals (CH2CN) produced by homolytic breaking of acetonitrile (CH3CN), which present an almost ideal (98%) site selectivity to bind covalently to graphene on these areas. The subsequent specific reaction of the cyanomethyl radicals with TCNQ is observed in the real space by STM and STS, which reveals the specific character of the bond formed.

Published
2017
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2. Energy gap opening by crossing drop cast single-layer graphene nanoribbons.

Author

Toyo Kazu Yamada, Hideto Fukuda, Taizo Fujiwara, Polin Liu, Kohji Nakamura, Seiya Kasai, Amadeo L Vazquez de Parga, and Hirofumi Tanaka

Subjects
BAND gaps, GRAPHENE, NANORIBBONS
Abstract

Band gap opening of a single-layer graphene nanoribbon (sGNR) sitting on another sGNR, fabricated by drop casting GNR solution on Au(111) substrate in air, was studied by means of scanning tunneling microscopy and spectroscopy in an ultra-high vacuum at 78 K and 300 K. GNRs with a width of ∼45 nm were prepared by unzipping double-walled carbon nanotubes (diameter ∼15 nm) using the ultrasonic method. In contrast to atomically-flat GNRs fabricated via the bottom-up process, the drop cast sGNRs were buckled on Au(111), i.e., some local points of the sGNR are in contact with the substrate (d ∼ 0.5 nm), but other parts float (d ∼ 1–3 nm), where d denotes the measured distance between the sGNR and the substrate. In spite of the fact that the nanoribbons were buckled, dI/dV maps confirmed that each buckled sGNR had a metallic character (∼3.5 Go) with considerable uniform local density of states, comparable to a flat sGNR. However, when two sGNRs crossed each other, the crossed areas showed a band gap between −50 and +200 meV around the Fermi energy, i.e., the only upper sGNR electronic property changed from metallic to p-type semiconducting, which was not due to the bending, but the electronic interactions between the up and down sGNRs. [ABSTRACT FROM AUTHOR]

Published
2018
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