Blanc SIMI 4 - Blanc - SIMI 4 - Physique des milieux condensés et dilués

Contacts and Ribbons of Graphène – CoRiGraph

High-resolution ARPES will allow us to characterize the overall quality of ribbons, while providing wave-vector resolved electronic structure. STM images will provide information about the top-layer structure of nanoribbons and scanning transmission electron microscopy (STEM) work will establish the stacking geometry of the graphene layers.

The main transport result of this year are the measurements at low temperature (GeorgiaTech) and in situ with 4 tip STM (Université Leibnitz at Hannover). These results show that transport is one-dimensional, quantified and balistic even at RT for lengths of up to 15µm. On this ribbons, we have also observed a band gap opening in the short dimension of the ribbon, maybe associated to quantum confinement. From photoemission measurements, this region could be located at a region near the ribbon.

Next year we intend to study the atomic structure of the ribbons as well as the electronic properties of graphene/metal interfaces. We will also study the spin transport properties in ribbons.

We are preparing a commun publication to three out of four parteners of the ANR.

Submission summary

A major technological challenge is the finding of a new material for the postsilicon CMOS era. Graphene exhibits the excellent properties of carbon nanotubes (CNT), while not suffering from placing and scalability problems. Epitaxial graphene is the most viable candidate for high-speed low power nano-electronics device applications as recognized by the industry. The principal challenges are the access contact resistance, how to retain high mobility in graphene with a top-gate while preserving graphene edge quality after lithographic processing of the short channel required for high frequency operation. Another almost unexplored avenue for graphene is ballistic nanoelectronics. Pristine CNTs are known to be ballistic conductors even at RT. Graphene ribbons have similar properties and are thus interesting for all-graphene circuitry, for they are claimed to have better mobility and stand higher current densities than Cu wires.
Graphene nanoribbons can be produced in epitaxial graphene by non-lithographic techniques on the sidewall of pre-etched SiC steps. This technique is scalable as already demonstrated by the fabrication of 10,000 transistors on a single chip. Moreover, transport data suggest smooth edges since disordered-related effects (localization, transport gap) are not observed. These ribbons may be the needed breakthrough in graphene electronics, opening new possibility of ballistic transport, non linear effect in ballistic junctions and new all-graphene interconnects. This opens the way for electronics based on ballistic transport and coherent effects, which cannot be realized in conventional semiconductors. The primary goal of this project is thus to study graphene nanoribbons grown on SiC sidewalls, and compare them with lithographically etched ribbons. Metal contacts on graphene, a key issue to any device fabrication will also studied, with the challenge that almost nothing wets graphene. This project aims to study by STM, photoemission, and electronic microscopy the atomic structure of sidewall nanoribbons, their local and average electronic properties, defects, and electronic properties. Metal/graphene interfaces serving as model systems for electric contacts will also be investigated. In short, the main objective of CoRiGraf project is to study open questions on graphene sidewall nanoribbons and on metal/graphene interfaces about their atomic and electronic structure, which can be properly addressed with the complementary set of experimental techniques and reknown expertise (ARPES, STM/STS, STEM) and calculations (quantum transport) available at the consortium.

Project coordination

Antonio Tejeda (Institut Jean Lamour) – antonio.tejeda@u-psud.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

LPS Laboratoire de Physique des Solides
INEEL Institut Néel
SOLEIL Synchrotron SOLEIL
IJL Institut Jean Lamour

Help of the ANR 510,952 euros
Beginning and duration of the scientific project: December 2012 - 42 Months

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