Carbon forms a variety of allotropes (structures) due to the diverse hybridization of s- and p-electron orbitals, time-honored graphite (two-dimensional structure) and diamond (three-dimensional network), new forms such as C60 fullerene (cage structure), nanotubes (quasi-one-dimensional structure), graphene (truly two-dimensional network), and carbyne (truly one-dimensional chain). The family of new allotropes (fullerene, nanotubes, graphene, carbyne) are called “nanostructured carbon” or “nanocarbon”. They exhibit extreme properties, such as ultrahigh mechanical strength, ultrahigh charge carrier mobility, high thermal conductivity, and so on, thus attracting considerable attention for electronic and mechanical applications as well as in basic materials science for exploring new physics and chemistry.
Carbon nanotubes (CNTs) and graphene possess excellent properties as electron field-emitters owing to their excellent properties. Electron sources are important in a wide range of areas from basic physics and scientific instruments to medical and industrial applications. CNTs and graphene are unique as field emitters and offer several benefits compared to traditional cathodes (e.g., thermionic and photocathodes). Field emission produces very intense electron currents from a small surface area with a narrow energy spread, providing a highly coherent electron beam. The combination of high current, small source size, and narrow energy distribution not only provides us with the brightest electron sources but also explores a new field of electron-beam-related research.
This book describes recent progress of research on nanocarbon field electron emitters ranging from fundamental properties to promising applications, such as X-ray sources, vacuum electronic devices, space thrusters, and so on.
