Graphene has been attracting great interest because of its distinctive band structure and physical properties. Today, graphene is limited to small sizes because it is produced mostly by exfoliating graphite. We grew large-area graphene films of the order of centimeters on copper substrates by chemical vapor deposition using methane. The films are predominantly single-layer graphene, with a small percentage (less than 5%) of the area having few layers, and are continuous across copper surface steps and grain boundaries. The low solubility of carbon in copper appears to help make this growth process self-limiting. We also developed graphene film transfer processes to arbitrary substrates, and dual-gated field-effect transistors fabricated on silicon/silicon dioxide substrates showed electron mobilities as high as 4050 square centimeters per volt per second at room temperature.

/pdf/large-area-synthesis-of-high-quality-and-uniform-graphene-1mcd5d9hvr.pdf

Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils

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.

/pdf/transfer-of-large-area-graphene-films-for-high-performance-303u6jmug6.pdf

Transfer of large-area graphene films for high-performance transparent conductive electrodes

We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.

/pdf/science-and-technology-roadmap-for-graphene-related-two-4q9m7czlkc.pdf

Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

In the last three decades, zero-dimensional, one-dimensional, and two-dimensional carbon nanomaterials (i.e., fullerenes, carbon nanotubes, and graphene, respectively) have attracted significant attention from the scientific community due to their unique electronic, optical, thermal, mechanical, and chemical properties. While early work showed that these properties could enable high performance in selected applications, issues surrounding structural inhomogeneity and imprecise assembly have impeded robust and reliable implementation of carbon nanomaterials in widespread technologies. However, with recent advances in synthesis, sorting, and assembly techniques, carbon nanomaterials are experiencing renewed interest as the basis of numerous scalable technologies. Here, we present an extensive review of carbon nanomaterials in electronic, optoelectronic, photovoltaic, and sensing devices with a particular focus on the latest examples based on the highest purity samples. Specific attention is devoted to each class of carbon nanomaterial, thereby allowing comparative analysis of the suitability of fullerenes, carbon nanotubes, and graphene for each application area. In this manner, this article will provide guidance to future application developers and also articulate the remaining research challenges confronting this field.

Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing

Owing in part to complementary metal-oxide-semiconductor (CMOS) scaling issues, the semiconductor industry is placing an increased emphasis on emerging materials and devices that may provide a solution beyond the 22-nm node. Single and few layers of carbon sheets (graphene) have been fabricated by a variety of techniques including mechanical exfoliation and chemical vapor deposition, and field-effect devices have been demonstrated with room temperature field-effect mobilities close to 10 000 cm2/Vs. But since graphene is a gapless semiconductor, these transistors have high off-state leakage and nonsaturating drive currents. This is problematic for digital logic, but is acceptable for analog device applications such as low-noise amplifiers and radio-frequency (RF)/millimeter-wave field-effect transistors (FETs). The remarkable transport physics of graphene due to its linear bandstructure have led to novel beyond CMOS logic devices as well, such as “pseudospin” devices.

Graphene for CMOS and Beyond CMOS Applications

The Bilayer pseudo-spin Field Effect Transistor (BiSET) has been proposed as one means of taking advantage of possible room temperature superfluidity in two graphene layers separated by a thin dielectric. In principle, the switching energy per device could be on the scale of 10 zJ, over two orders of magnitude below estimates for "end-of the roadmap" CMOS transistors. However, achieving both the goal of room temperature superfluidity and harnessing it for low-power switching pose substantial challenges, both theoretical and experimental. In this work we review the basic graphene superfluidity and BiSFET concepts, our current

Bilayer Pseudo-Spin Field Effect Transistor (BiSFET): Concepts and Critical Issues for Realization

In this paper we describe three methods that can be used to measure the transient response of organic and polymer field-effect transistors (FETs) and also how such measurements can be used to determine the drift mobility and velocity. The first method measures the response of a FET to a step voltage applied to the source with the gate grounded and the drain held at close to ground, while the second uses a ramp input to the source. The third technique evaluates the frequency response of the FET, connected as a diode, to a large-signal alternating voltage. We show that important information can be obtained from such measurements which can be quantitatively interpreted with the help of models that we are developing. In general, there is good agreement between the drift mobility measured with these approaches and the field-effect mobility calculated from transistor output and transfer characteristics. The specific results we present in this paper are for pentacene devices; however, other recent work by our group indicates that these results are more general.

Dynamic characterization of charge transport in organic and polymer transistors

Introduction The bilayer pseudospin field effect transistor (BiSFET) is intended to enable much lower voltage and power operation than possible with complementary metal–oxide–semiconductor (CMOS) field effect transistor (FET)-based logic [1, 2]. The ultimate limits of CMOS are not due to fabrication technology limitations. Rather, they are intrinsic to its operating principles, defined by basic physics such as charge carrier thermionic emission over the channel barrier and quantum mechanical tunneling through it. New operating principles are required. The BiSFET relies on the possibility of room temperature excitonic (electron-hole) superfluid condensation in two dielectrically separated graphene layers [3, 4]. While the physics is interesting in its own right, from the device point of view this many-body physics brings with it the possibility of a strong sensitivity to sub-thermal voltages (sub- k B T / q voltages, where k B is Boltzmann’s constant, T is the temperature in Kelvin, and q is the magnitude of electron charge) in the current–voltage ( I – V ) characteristics [5–7]. With power consumption proportional to the square of voltage, use of voltages on the scale of or less than room temperature k B T / q ≈ 26 mV offers order of magnitude reductions in switching energies as compared to even end-of-the roadmap CMOS [8]. Circuit simulation with 25 mV power supplies show switching energies on the scale of 10 zeptojoules (zJ) per BiSFET (where 1 zJ = 10 –21 J = 10 –3 aJ)! However, with this potential for voltage reduction also come I – V characteristics much different from those of MOSFETs that must be worked around at worst, and may provide new circuit opportunities at best. In terms of interconnects, information would continue to be passed via charge among devices. In this way, BiSFETs would also be compatible with existing electronic devices after voltage level shifts.

Bilayer pseudospin field effect transistor

Owing in part to complementary metal-oxide- semiconductor (CMOS) scaling issues, the semiconductor industry is placing an increased emphasis on emerging materials and devices that may provide a solution beyond the 22-nm node. Single and few layers of carbon sheets (graphene) have been fabricated by a variety of techniques including mechanical exfoliation and chemical vapor deposition, and field-effect devices have been demonstrated with room tem- perature field-effect mobilities close to 10 000 cm 2 /Vs. But since graphene is a gapless semiconductor, these transistors have high OFF-state leakage and nonsaturating drive currents. This is problematic for digital logic, but is acceptable for analog device applications such as low-noise amplifiers and radio- frequency (RF)/millimeter-wave field-effect transistors (FETs). The remarkable transport physics of graphene due to its linear bandstructure have led to novel beyond CMOS logic devices as well, such as Bpseudospin( devices.

Graphene for CMOS and Beyond CMOS Applications The unique properties of graphene, which consists of a few layers of carbon atoms, are discussed in this paper.

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