Alfa Chemistry provides testing services to analyze graphene layers and thickness. The number of layers is directly related to the quality of graphene products and have a greater impact on its electrical and thermal conductivity properties. We use various effective methods to test and analyze unprocessed graphene and devices made from it. Alfa Chemistry's analysis and testing capabilities can meet your personalized data analysis needs and provide comprehensive data analysis results.
Our Instrument Platform for Layers and Thickness Analysis
- Scanning Electron Microscope
- The number of graphene layers can be directly observed.
- Information such as size and area can also be obtained.
- When graphene has wrinkles or folds, the accuracy is reduced.
- The observation range is small. It is used to analyze single-layer or double-layer graphene generally.
Atomic Force Microscopy (AFM) is the most direct and effective tool for graphene layer characterization.
Advantage:
Disadvantage:
Figure 1. AFM image of CVD-grown graphene transferred onto a SiO2 substrate. (Srivastava A, et al, 2010)
- Transmission Electron Microscopy
- It is impossible to accurately judge the number of graphene layers, especially single-layer and double-layer.
- When graphene has wrinkles or folds, the accuracy is reduced.
High-resolution electron micrographs at the edges or wrinkles of graphene can be used to estimate the layer and size of graphene sheets.
Advantage: Simple and fast.
Disadvantages:
Figure 2. TEM images of folded edges for monolayer and bilayer graphene, respectively. (Meyer J.C, et al, 2007)
- Raman Spectroscopy
- RS is suitable for AB stacking graphene. For graphene prepared by other methods, the stacking method is rather messy so that RS cannot be used to accurately distinguish the layers.
- The RS results are related to the defects of graphene crystals and surface adsorbed substances.
The single Lorentz-type second-order Raman peak (G' peak) is a simple and effective method for the determination of single-layer graphene. The number of graphene sheets can be characterized by the shape of the G'peak in the RS spectrum.
Available range:
Figure 3. (a) Raman spectra of graphene with 1~4 layers; (b) Raman G' band of graphene with 1~4 layers. (Wu J.X, et al, 2014)
- Scanning Tunneling Microscope (STM)
STM can provide atomic-level structural information on the surface of graphene. It can perfectly present the hexagonal honeycomb lattice structure of graphene. STM testing usually requires the substrate to be conductive, so graphene or silicon carbide epitaxial growth grown by metal-catalyzed CVD is the best sample for STM characterization.
- Optical Microscopy
Optical microscopy is limited to substrates that are significantly different from graphene in contrast.
Figure 5. Optical microscopy images of graphene with different layers. (Ni Z.H, et al, 2007)
Detectable Samples Include:
Graphene, graphene oxide, reduced graphene oxide, CVD graphene, nanographene and etc.
The Standard we Follow:
GB/T 30544.13-2018 ISO/TS 80004-13:2017(en): Graphene and Related Two-dimensional (2D) Materials.
Why Us?
1. Alfa Chemistry laboratory adopts ISO/IEC17025 international laboratory management system.
2. Complete qualifications, a large number of instruments, and a strong scientific research team
3. The detection cycle is short and well designed experiment procedure.
References
- Ni Z.H, et al. (2007). "Graphene Thickness Determination Using Reflection and Contrast Spectroscopy." Nano Lett. 7(9), 2758-2763.
- Srivastava A, et al. (2010). "Novel Liquid Precursor-Based Facile Synthesis of Large-Area Continuous, Single, and Few-Layer." Chemistry of Materials. 22(11), 3457-3461.
- Meyer J.C, et al. (2007). "The structure of suspended graphene sheets." Nature. 446, 60-63.
- Wu J.X, et al. (2014). "The structure of suspended graphene sheets." Acta Chim. Sinica. 72, 301-318.
