Raman Spectroscopy in Graphene-Based Systems: Prototypes for Nanoscience and Nanometrology

Abstract

Raman spectroscopy is a powerful tool to characterize the different types of sp 2 carbon nanostructures, including two-dimensional graphene, one-dimensional nanotubes, and the effect of disorder in their structures. This work discusses why sp 2 nanocarbons can be considered as prototype materials for the development of nanoscience and nanometrology. The sp 2 nanocarbon structures are quickly introduced, followed by a discussion on how this field evolved in the past decades. In sequence, their rather rich Raman spectra composed of many peaks induced by single-and multiple-resonance effects are introduced. The properties of the main Raman peaks are then described, including their dependence on both materials structure and external factors, like temperature, pressure, doping, and environmental effects. Recent applications that are pushing the technique limits, such as multitechnique approach and in situ nanomanipulation, are highlighted, ending with some challenges for new developments in this field.

Kinetics of defect formation in chemically vapor deposited (CVD) graphene during laser irradiation: The case of Raman investigation

“…There is another Raman feature, the D' peak, located at ≈1600 cm −1 , and ascribed to states lying at the zigzag boundaries, whereas the D peak, is associated to armchair boundaries [17]. In all our investigations, however, the D' peak has never been observed, suggesting a higher formation energy for this kind of defects.…”

“…Raman spectroscopy is often employed to estimate the average grain dimension, which correlates well with the ID/IG intensity ratio [17]. This reasoning bases on the observation that most of the defects are located at grain boundaries.…”

Investigation of Different Pre-Treated Multi-Walled Carbon Nanotubes by Raman Spectroscopy

“…However, MWCNT do not exhibit uniform structures, and therefore, require cleaning processes in order to guarantee a uniform base material prior to any modification or direct application [2]. In this work, we use co-axial structured MWCNT composed of monoatomic sheets of polyaromatic sp 2 hybridized carbon layers (equivalent of graphene) which are rolled into cylinders to form highly entangled networks [3].…”

“…The fitting procedure employed in this work focuses on three signals which arise from resonant singlephonon lattice vibrations between 1300 cm −1 and 1700 cm −1 . The three bands are referred to the G-band, representative for the pristine graphitic lattice vibration E 2g (q = 0) with no change of the dipole momentum, and the D-and D'-bands for lattice vibrations E 2g (q ≠ 0) and A 1g , which are induced by structural defects [3]. Molecular vibrations are not considered in this fitting procedure.…”

Surface‐enhanced Raman spectra on graphene

“…The dispersion comes from the slope of the Dirac cone; therefore, changes in the dispersion reflect changes in the electronic structure of the graphene. [5,6] In case that structural imperfections are present in a graphene sample, one can also observe the defect scattering related D and D' modes at around 1,350 and 1,620 cm −1 , respectively. As reported by several authors previously, the enhancement of a particular Raman mode of graphene depends on the excitation energy of the laser and plasmonic characteristics of the metallic structure in contact with the graphene, and consequently, the enhancement factors for the D, D', G, and 2D modes can be very different.…”