The model and theoretical understanding of the Raman spectra in disordered and amorphous carbon are given. The nature of the G and D vibration modes in graphite is analyzed in terms of the resonant excitation of π states and the long-range polarizability of π bonding. Visible Raman data on disordered, amorphous, and diamondlike carbon are classified in a three-stage model to show the factors that control the position, intensity, and widths of the G and D peaks. It is shown that the visible Raman spectra depend formally on the configuration of the ${\mathrm{sp}}^2$ sites in ${\mathrm{sp}}^2$-bonded clusters. In cases where the ${\mathrm{sp}}^2$ clustering is controlled by the ${\mathrm{sp}}^3$ fraction, such as in as-deposited tetrahedral amorphous carbon (ta-C) or hydrogenated amorphous carbon (a-C:H) films, the visible Raman parameters can be used to derive the ${\mathrm{sp}}^3$ fraction.

Graphene is the two-dimensional building block for carbon allotropes of every other dimensionality. We show that its electronic structure is captured in its Raman spectrum that clearly evolves with the number of layers. The $D$ peak second order changes in shape, width, and position for an increasing number of layers, reflecting the change in the electron bands via a double resonant Raman process. The $G$ peak slightly down-shifts. This allows unambiguous, high-throughput, nondestructive identification of graphene layers, which is critically lacking in this emerging research area.

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.

The Raman spectra of a wide range of disordered and amorphous carbons have been measured under excitation from 785 to 229 nm. The dispersion of peak positions and intensities with excitation wavelength is used to understand the nature of resonant Raman scattering in carbon and how to derive the local bonding and disorder from the Raman spectra. The spectra show three basic features, the D and G around 1600 and 1350 ${\mathrm{cm}}^{\mathrm{-}1}$ for visible excitation and an extra T peak, for UV excitation, at ∼1060 ${\mathrm{cm}}^{\mathrm{-}1}$. The G peak, due to the stretching motion of ${\mathrm{sp}}^2$ pairs, is a good indicator of disorder. It shows dispersion only in amorphous networks, with a dispersion rate proportional to the degree of disorder. Its shift well above 1600 ${\mathrm{cm}}^{\mathrm{-}1}$ under UV excitation indicates the presence of ${\mathrm{sp}}^2$ chains. The dispersion of the D peak is strongest in ordered carbons. It shows little dispersion in amorphous carbon, so that in UV excitation it becomes like a density-of-states feature of vibrations of ${\mathrm{sp}}^2$ ringlike structures. The intensity ratio $I\left(D\right)/I\left(G\right)\mathrm{}$ falls with increasing UV excitation in all forms of carbon, with a faster decrease in more ordered carbons, so that it is generally small for UV excitation. The T peak, due to ${\mathrm{sp}}^3$ vibrations, only appears in UV Raman, lying around 1060 ${\mathrm{cm}}^{\mathrm{-}1}$ for H-free carbons and around 980 ${\mathrm{cm}}^{\mathrm{-}1}$ in hydrogenated carbons. In hydrogenated carbons, the ${\mathrm{sp}}^3{\mathrm{C}-\mathrm{H}}_x$ stretching modes around 2920 ${\mathrm{cm}}^{\mathrm{-}1}$ can be clearly detected for UV excitation. This assignment is confirmed by deuterium substitution.

Raman spectroscopy is a standard characterization technique for any carbon system. Here we review the Raman spectra of amorphous, nanostructured, diamond–like carbon and nanodiamond. We show how to use resonant Raman spectroscopy to determine structure and composition of carbon films with and without nitrogen. The measured spectra change with varying excitation energy. By visible and ultraviolet excitation measurements, the G peak dispersion can be derived and correlated with key parameters, such as density, sp³ content, elastic constants and chemical composition. We then discuss the assignment of the peaks at 1150 and 1480 cm⁻¹ often observed in nanodiamond. We review the resonant Raman, isotope substitution and annealing experiments, which lead to the assignment of these peaks to trans–polyacetylene.