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November 10, 2009

Progress Making Large Batches of Graphene Suitable for Computers and Electronics

1.

Nanoletters: Transfer-Free Batch Fabrication of Single Layer Graphene Transistors

Full integration of graphene into conventional device circuitry would require a reproducible large scale graphene synthesis that is compatible with conventional thin film technology. We report the synthesis of large scale single layer graphene directly onto an evaporated copper film. A novel fabrication method was used to directly pattern these graphene sheets into devices by simply removing the underlying copper film. Raman and conductance measurements show that the mechanical and electrical properties of our single layer graphene are uniform over a large area, (Ferrari, A. C. et al. Phys. Rev. Lett. 2006, 97, 187401.) which leads to a high device yield and successful fabrication of ultra long (>0.5 mm) graphene channels. Our graphene based devices present excellent electrical properties including a promising carrier mobility of 700 cm^2/V·s and current saturation characteristics similar to devices based on exfoliated graphene (Meric, I.. et al. Nat Nanotechnol. 2008, 3, 654−659).


8 page pdf of supplemental information



2.

(6 page pdf) Nanoletters: Free-Standing Epitaxial Graphene

We report on a method to produce free-standing graphene sheets from epitaxial graphene on silicon carbide (SiC) substrate. Doubly clamped nanomechanical resonators with lengths up to 20 μm were patterned using this technique and their resonant motion was actuated and detected optically. Resonance frequencies of the order of tens of megahertz were measured for most devices, indicating that the resonators are much stiffer than expected for beams under no tension. Raman spectroscopy suggests that the graphene is not chemically modified during the release of the devices, demonstrating that the technique is a robust means of fabricating large-area suspended graphene structures



3. Transfer of Large-Area Graphene Films for High-Performance Transparent Conductive Electrodes

Graphene, a two-dimensional monolayer of sp2-bonded carbon atoms, has been attracting great interest due to its unique transport properties. One of the promising applications of graphene is as a transparent conductive electrode owing to its high optical transmittance and conductivity. In this paper, we report on an improved transfer process of large-area graphene grown on Cu foils by chemical vapor deposition. The transferred graphene films have high electrical conductivity and high optical transmittance that make them suitable for transparent conductive electrode applications. The improved transfer processes will also be of great value for the fabrication of electronic devices such as field effect transistor and bilayer pseudospin field effect transistor devices.



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