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

A highly ordered gold nanodot array was fabricated by vacuum evaporation using an anodic porous alumina membrane with through-holes of nanometer scale as a mask. This technique resulted in an orderly arrangement of Au dots with a diameter of approximately 40 nm over a large area on a Si substrate.

https://iopscience.iop.org/article/10.1143/JJAP.35.L126/pdf

Fabrication of gold nanodot array using anodic porous alumina as an evaporation mask

Carbon nanotubes, a novel form of carbon discovered in 1991, have been rapidly recognized as one of the most promising electron field emitters ever since the first emission experiments reported in 1995. Their potential as emitters in various devices has been amply demonstrated during the last five years, and recent developments of production techniques are likely to trigger future applications. This report reviews the state of the art of the current research on the electron field emission properties of carbon nanotubes and surveys their ability to provide single or multiple electron sources.

Field emission from carbon nanotubes: the first five years

Field emission (FE) is based on the physical phenomenon of quantum tunneling, in which electrons are injected from the surface of materials into vacuum under the influence of an applied electric field. A variety of field emission cold cathode materials have been developed to date. In this review, we shall focus on several kinds of novel cold cathode materials that have been developed in the past decade. These include materials for microfabricated field-emitter arrays, diamond and related films, carbon nanotubes, other quasi one-dimensional nanomaterials and printable composite materials. In addition, cold cathode materials have a wide range of applications such as in flat panel displays, high-power vacuum electronic devices, microwave-generation devices, vacuum microelectronic devices and vacuum nanoelectronic devices. Applications are in consumer goods, military industries and also space technology. A comprehensive overview of the various applications is presented. Recently, recognizing the strong possibility that vacuum nanoelectronic devices using quasi one-dimensional nanomaterials, such as carbon nanotubes may emit electrons with driving voltages comparable to that of a solid-state device, there is a growing interest in novel applications of such devices. With such exciting opportunities, there is now a flurry of activities to explore applications far beyond those considered for the conventional hot cathodes that operate on thermionic emission. We shall discuss the details of a number of fascinating potential applications.

Novel cold cathode materials and applications

A handheld and battery-operated far-ultraviolet plane-emission device is demonstrated. The device has low current consumption and stable operation at an output power of 0.2 mW at 225 nm, and may be useful in photochemical and biotechnological applications such as photo catalysis, sterilization and the modification of chemical substances.

Far-ultraviolet plane-emission handheld device based on hexagonal boron nitride

Field emission cathodes fabricated using thin-film techniques and electron beam microlithography are described, together with effects obtained by varying the fabrication parameters. The emission originates from the tip of molybdenum cones that are about 1.5 micron tall with a tip radius around 500 A. Such cathodes have been produced in closely packed arrays containing 100 and 5000 cones as well as singly. Maximum currents in the range 50-150 microamp per cone can be drawn. Life tests with the 100-cone arrays drawing 2 mA total emission (or 3 A per sq cm) have proceeded in excess of 7000 hr with about a 10% drop in emission current. Studies are presented of the emission characteristics and current fluctuation phenomena. It is tentatively concluded that the emission arises from only one or a few atomic sites on the cone tips.

L. Humphrey

Papers

Physical properties of thin‐film field emission cathodes with molybdenum cones