The outstanding electrical, mechanical and chemical properties of graphene make it attractive for applications in flexible electronics. However, efforts to make transparent conducting films from graphene have been hampered by the lack of efficient methods for the synthesis, transfer and doping of graphene at the scale and quality required for applications. Here, we report the roll-to-roll production and wet-chemical doping of predominantly monolayer 30-inch graphene films grown by chemical vapour deposition onto flexible copper substrates. The films have sheet resistances as low as approximately 125 ohms square(-1) with 97.4% optical transmittance, and exhibit the half-integer quantum Hall effect, indicating their high quality. We further use layer-by-layer stacking to fabricate a doped four-layer film and measure its sheet resistance at values as low as approximately 30 ohms square(-1) at approximately 90% transparency, which is superior to commercial transparent electrodes such as indium tin oxides. Graphene electrodes were incorporated into a fully functional touch-screen panel device capable of withstanding high strain.

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Roll-to-roll production of 30-inch graphene films for transparent electrodes

Recent years have seen a rapid growth of interest by the scientific and engineering communities in the thermal properties of materials. Heat removal has become a crucial issue for continuing progress in the electronic industry, and thermal conduction in low-dimensional structures has revealed truly intriguing features. Carbon allotropes and their derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials span an extraordinary large range--of over five orders of magnitude--from the lowest in amorphous carbons to the highest in graphene and carbon nanotubes. Here, I review the thermal properties of carbon materials focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder. Special attention is given to the unusual size dependence of heat conduction in two-dimensional crystals and, specifically, in graphene. I also describe the prospects of applications of graphene and carbon materials for thermal management of electronics.

Thermal properties of graphene and nanostructured carbon materials

Recent years witnessed a rapid growth of interest of scientific and engineering communities to thermal properties of materials. Carbon allotropes and derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials span an extraordinary large range – of over five orders of magnitude – from the lowest in amorphous carbons to the highest in graphene and carbon nanotubes. I review thermal and thermoelectric properties of carbon materials focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder. A special attention is given to the unusual size dependence of heat conduction in two-dimensional crystals and, specifically, in graphene. I also describe prospects of applications of graphene and carbon materials for thermal management of electronics.

Thermal Properties of Graphene, Carbon Nanotubes and Nanostructured Carbon Materials

The discovery of uniform deposition of high-quality single layered graphene on copper has generated significant interest. That interest has been translated into rapid progress in terms of large area deposition of thin films via transfer onto plastic and glass substrates. The opto-electronic properties of the graphene thin films reveal that they are of very high quality with transmittance and conductance values of >90% and 30Ω/sq, both are comparable to the current state-of-the-art indium tin oxide transparent conductor. In this Feature Article, we provide a detailed and up to date description of the literature on the subject as well as highlighting challenges that must be overcome for the utilization of graphene deposited on copper substrates by chemical vapour deposition.

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A review of chemical vapour deposition of graphene on copper

Chemical vapour deposition is a promising route for large-scale graphene growth. It is now shown that—through the use of seeds—high-quality, large, single-crystal domains can be grown on a patterned arrangement, and can be used to carefully study the transport across grain boundaries.

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Control and characterization of individual grains and grain boundaries in graphene grown by chemical vapour deposition

We report on electronic properties of graphene synthesized by chemical vapor deposition (CVD) on copper then transferred to SiO2/Si. Wafer-scale (up to 4 in.) graphene films have been synthesized, consisting dominantly of monolayer graphene as indicated by spectroscopic Raman mapping. Low temperature transport measurements are performed on microdevices fabricated from such CVD graphene, displaying ambipolar field effect (with on/off ratio ∼5 and carrier mobilities up to ∼3000 cm2/V s) and “half-integer” quantum Hall effect, a hall-mark of intrinsic electronic properties of monolayer graphene. We also observe weak localization and extract information about phase coherence and scattering of carriers.

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Electronic transport in chemical vapor deposited graphene synthesized on Cu: Quantum Hall effect and weak localization

a Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 b School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907 c Department of Mechanical Engineering, Iowa State University, Ames, IA 50011 d School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 e Department of Electrical and Computer Engineering, University of Houston, Houston, Texas 77204 f Department of Physics, Purdue University, West Lafayette, IN 47907 g School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907

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Thermal Transport in Graphene Nanostructures: Experiments and Simulations

The use of a graphene field-effect transistors (GFETs) to detect radiation is proposed and analyzed. The detection mechanism used in the proposed detector architecture is based on the high sensitivity of graphene to the local change of electric field that can result from the interaction of radiation with a gated undoped semiconductor absorber (substrate) in a GFET. We have modeled a GFET-based radiation detector, and discussed its anticipated performance and potential advantages compared to conventional detector architectures.

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Graphene Field-Effect Transistors on Undoped Semiconductor Substrates for Radiation Detection

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Electronic transport in chemical vapor deposited graphene synthesized on Cu: Quantum Hall effect and weak localization (vol 96, 122106, 2010)

In one embodiment, the present invention provides the description of an inexpensive and disposable handheld device for detecting Circulating tumor cells (CTC) in blood called a handheld CTC detector (HCTCD) The HCTCD is capable of detecting less than 1 CTC per milliliter The HCTCD consists of a dense array of high aspect ratio freestanding metallic nanoneedles, functionalized with antibodies that integrated within a microfluidic device and selectively capture and count (using electrical signal detection) the CTCs By selecting a right functionalization protocol for the nanoneedles array, the HCTCD can be used for selective capturing a variety of rare cells that are mixed in human fluids

Romaneh Jalilian

Papers

Electronic transport in chemical vapor deposited graphene synthesized on Cu: Quantum Hall effect and weak localization

Thermal Transport in Graphene Nanostructures: Experiments and Simulations

Graphene Field-Effect Transistors on Undoped Semiconductor Substrates for Radiation Detection

Electronic transport in chemical vapor deposited graphene synthesized on Cu: Quantum Hall effect and weak localization (vol 96, 122106, 2010)

Apparatus and methods for detection of tumor cells in blood