Raman spectroscopy of graphene on different substrates and influence of defects

Abstract

We show the evolution of Raman spectra with a number of graphene layers on different substrates, SiO 2 /Si and conducting indium tin oxide (ITO) plate. The G mode peak position and the intensity ratio of G and 2D bands depend on the preparation of sample for the same number of graphene layers. The 2D Raman band has characteristic line shapes in single and bilayer graphene, capturing the differences in their electronic structure. The defects have a significant influence on the G band peak position for the single layer graphene: the frequency shows a blue shift up to 12 cm -1 depending on the intensity of the D Raman band, which is a marker of the defect density. Most surprisingly, Raman spectra of graphene on the conducting ITO plates show a lowering of the G mode frequency by ~ 6 cm -1 and the 2D band frequency by ~ 20 cm -1 . This red-shift of the G and 2D bands is observed for the first time in single layer graphene.

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“…All of the types of investigated graphene exhibited very similar Raman spectra. This confirmed the presence of single/bilayer graphene with a typical ratio of intensity and a full width at half maximum (FWHM) of the selected Raman peaks (Table 2) [19,20]. Based on the SEM and TEM analyses (Fig.…”

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“…For an SLG, I G /I 2D intensity ratio is ∼0.24 which increases with the number of graphene layers thus making it possible to estimate the thickness of graphene layers. [21,22] In this regard, it is well known that the I G /I 2D ratio increases up to six to eight layers. In order to measure the actual thickness of the graphene sample and obtain the number of layers, sensitive metrology techniques such as AFM analysis or a high resolution TEM technique may be utilized.…”