Building Blocks for Integrated Graphene Circuits

Abstract

The observation of single sheets of graphite (graphene) presents new possibilities for carbon-based nanoelectronics. We report defect tolerant configurations for a nearly reflectionless 120°turn and nearly reflectionless symmetric and asymmetric splitters, which can be cut from graphene. Connections between zigzag strips of different widths can be made with either low or high reflectance depending on the connection shape.The recent observation of isolated graphite sheets (graphene) supported by insulating substrates 1-4 provides new possibilities for carbon-based nanoelectronics. The potential importance of graphene as an electronic material is partially based upon the following properties: (1) Easy atomic plane lamination and strong bonding within the plane make graphene fabrication technologically accessible through both mechanical exfoliation 2,3 and epitaxial growth. 4 (2) Devices and integrated circuits (ICs) could be processed from a graphene sheet using the existing planar technologies: electron-or ion-beam lithography 5-7 or direct focused electron 8 or ion-beam 9 writing. The latter two could be very precise because of the low electron or ion flux required for carving a single atomic plane, which decreases the Coulomb repulsion between particles in the beam and hence allows superior beam focusing. (3) The main building blocks of a graphene IC are graphene nanostrips (GNSs) 5-10 nm wide, which can have properties ranging from metallic to semiconducting depending on their widths and edges. 10 (4) Zigzag-edge GNSs have very low sensitivity to edge and substrate-induced disorder 11 and can transmit currents of an order of tens of microamps for voltage ranges 0.5-1.0 V in the absence of spin polarization along the edges. (5) In the single-channel regime, the ballistic length of GNSs can be comparable to the ballistic length of carbon nanotubes in the presence of substrate-induced disorder. 11 (6) Low scattering in the single-channel regime, including suppression of acoustic phonon scattering, 12 allows high current densities through GNSs with low heat dissipation, making them promising materials for Terahertz ICs.The above properties have already stimulated research on nanostrips fabrication 4,13,14 and will most likely result in attempts to create all-graphene electronic nanodevices and circuits patterned from either a single graphene plane or multiple planes separated by layers of insulating material. Either circuit concept requires passive elements and interconnects for wiring individual circuit elements. The wiring turns out to be a nontrivial issue because as we shall see only a few specific GNS patterns that have nearly ideal conductance and can transmit electron flux without losses. Most other patterns possess substantial reflectivity and cannot be used for wiring purposes despite their metallic nature. In this paper, we suggest geometrical configurations for (1) reflectionless interconnects and (2) highly reflective patterns analogous to resistors.Perhaps it is easiest to motivate these patte...

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