March 11, 2014 / Raman spectroscopy of Graphene Layers

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March 11, 2014 / Raman spectroscopy of Graphene Layers

 

Raman spectroscopy of Graphene Layers

 

3D Scanning Laser Raman Confocal Microscop

Interdisciplinary Research at the sub-micrometer range

  • Confocal Raman / fluorescence microscopy
  • Compact modular system
  • Wide spectral range (UV,VIS, IR)
  • High sensitivity
  • High temporal and thermal stability

 

Graphene has a number of unique properties (hardness, significant thermal and electrical conductivity, optical transparency, chemical stability), which makes it interesting for many applications.

To optimize technology of Graphene production, the need for measurement techniques with the capability to characterize structures with the high spatial resolution. Raman spectroscopy and microscopy are good candidates to characterize Graphene. These measurement methods are realized in Confotec MR520 (SOL instruments) confocal microscope. Raman spectroscopy and microscopy provide information about Graphene flake thickness, structural uniformity, etc.

In this document, we demonstrate the potential of Confotec MR520 to Graphene analysis.

The Raman measurements of Graphene were carried out in the confocal backscattering geometry using a 532 nm excitation laser, 100X objective. Graphene flakes were obtained by mechanical exfoliation of graphite and transferred onto SiO2/Si substrates (the SiO2 thickness is 300 nm). Thin flakes are sufficiently transparent, and change their interference color with respect to the thickness.  It it is relatively easy  to find a convenient graphene flake for Raman measurements.

Raman spectra are measured on Graphene multilayers on Si/ SiO2 are shown in Fig.1,2. Two most intense features are the G-peak at 1580 cm-1 and a 2D-band at 2700-2745 cm-1. Raman spectra show characteristic dependence on thickness of Graphene (Fig. 1,2). Relative Intensity of G-band enhances with the number of layers.  2D-peak becomes a broader a little and shifted to the higher wavenumbers with increasing the number of layers. Raman spectra of Graphene with more than 3 layers become hardly  distinguishable from each other.

 

Summary

Confotec MR520 has been used for nondestructive characterization of Graphene flakes. Raman spectra evolves clearly with the number of Graphene  layers.

 

 

 SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. confotec mr520 sait 800

Figure 1

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. grafen.fig1

Evolution of the Raman spectra with the number of graphene layers:
- yellow color - the single layer of graphene
- red color - 2 layers
- blue color - 3 layers and more

Figure 2

SOL instruments: спектрометр, рамановский микроскоп, эмиссионный спектрометр. grafen.fig2
G-band Intensity Raman Map of a graphene (15x 15 μm) flake