Atomic layer deposition: an overview.

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.

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

The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.

Electronics based on two-dimensional materials

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

Production, properties and potential of graphene

A comprehensive introduction and up-to-date reference to SiC power semiconductor devices covering topics from material properties to applications Based on a number of breakthroughs in SiC material science and fabrication technology in the 1980s and 1990s, the first SiC Schottky barrier diodes (SBDs) were released as commercial products in 2001. The SiC SBD market has grown significantly since that time, and SBDs are now used in a variety of power systems, particularly switch-mode power supplies and motor controls. SiC power MOSFETs entered commercial production in 2011, providing rugged, high-efficiency switches for high-frequency power systems. In this wide-ranging book, the authors draw on their considerable experience to present both an introduction to SiC materials, devices, and applications and an in-depth reference for scientists and engineers working in this fast-moving field . Fundamentals of Silicon Carbide Technology covers basic properties of SiC materials, processing technology, theory and analysis of practical devices, and an overview of the most important systems applications. Specifically included are:

Fundamentals of Silicon Carbide Technology: Growth, Characterization, Devices and Applications

Graphene is a hexagonally bonded sheet of carbon atoms that exhibits superior transport properties with a velocity of 108cm∕s and a room-temperature mobility of >15000cm2∕Vs. How to grow gate dielectrics on graphene with low defect states is a challenge for graphene-based nanoelectronics. Here, we present the growth behavior of Al2O3 and HfO2 films on highly ordered pyrolytic graphite (HOPG) by atomic layer deposition (ALD). To our surprise, large numbers of Al2O3 and HfO2 nanoribbons, with dimensions of 5–200nm in width and >50μm in length, are observed on HOPG surfaces at growth temperature between 200 and 250°C. This is due to the large numbers of step edges of graphene on HOPG surfaces, which serve as nucleation sites for the ALD process. These Al2O3 and HfO2 nanoribbons can be used as hard masks to generate graphene nanoribbons or as top-gate dielectrics for graphene devices. This methodology could be extended to synthesize insulating, semiconducting, and metallic nanostructures and their combinations.

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Atomic-layer-deposited nanostructures for graphene-based nanoelectronics

Top-gated, few-layer graphene field-effect transistors (FETs) fabricated on thermally decomposed semi-insulating 4H-SiC substrates are demonstrated. Physical vapor deposited SiO2 is used as the gate dielectric. A two-dimensional hexagonal arrangement of carbon atoms with the correct lattice vectors, observed by high-resolution scanning tunneling microscopy, confirms the formation of multiple graphene layers on top of the SiC substrates. The observation of n-type and p-type transition further verifies Dirac Fermions’ unique transport properties in graphene layers. The measured electron and hole mobilities on these fabricated graphene FETs are as high as 5400 and 4400cm2∕Vs, respectively, which are much larger than the corresponding values from conventional SiC or silicon.

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Top-gated graphene field-effect-transistors formed by decomposition of SiC

We report recent measurements of the drift velocity of electrons parallel to the basal plane in 6H and 4H silicon carbide (SiC) as a function of applied electric field. The dependence of the low field mobility and saturated drift velocity on temperature are also reported. The saturated drift velocities at room temperature are approximately 1.9/spl times/10/sup 7/ cm/s in 6H-SiC and 2.2/spl times/10/sup 7/ cm/s in 4H-SiC.

Measurement of high-field electron transport in silicon carbide

Comparisons are made between the carrier concentrations, ionization energies, and electron mobilities in 4H–SiC samples implanted with similar doses of nitrogen or phosphorus and annealed at 1300 or 1700 °C for 10 min in argon. The objective of the research is to determine which element may yield lower resistance 4H–SiC. Ionization energies of 53 and 93 meV are measured from phosphorus-implanted 4H–SiC, and are assigned to the hexagonal and cubic lattice positions in 4H–SiC, respectively. The corresponding ionization energies for nitrogen-implanted 4H–SiC are 42 and 84 meV, respectively. Phosphorus is not activated to the same extent that nitrogen is, and the carrier concentrations are about a factor of five lower for phosphorus-implanted 4H–SiC annealed at 1300 °C than for nitrogen-implanted 4H–SiC annealed at the same temperature. A higher mobility for phosphorus-implanted 4H–SiC is observed, but is not sufficiently high to offset the lower carrier concentration of this material. For the doses considered in this study, the resistivity of nitrogen-implanted 4H–SiC is lower than the resistivity of phosphorus-implanted 4H–SiC following anneals at either 1300 or 1700 °C.

James A. Cooper

Papers

Fundamentals of Silicon Carbide Technology: Growth, Characterization, Devices and Applications

Atomic-layer-deposited nanostructures for graphene-based nanoelectronics

Top-gated graphene field-effect-transistors formed by decomposition of SiC

Measurement of high-field electron transport in silicon carbide

Ionization energies and electron mobilities in phosphorus- and nitrogen-implanted 4H-silicon carbide