Graphene Research

Graphene Research

Graphene is a tightly packed layer of carbon atoms that are bonded together in a hexagonal honeycomb lattice. Only one atom thick (335 pm) but up to several micrometers in lateral extent, graphene shows many extraordinary material properties. As an electric conductor, it performs as well as copper. In terms of its ability to transport heat, it outperforms all other known materials. Optically it is highly transparent but completely impermeable to any other atoms. Harder than steel and also showing a high elasticity, graphene unites several astonishing material properties. This makes graphene one of the most scientifically investigated and promising materials for technical applications. Use ZEISS instruments for your investigations, whether you need the nano-patterning performance of an Ion Beam microscope, a high end light microscope with customized modules or the power of a field emission scanning electron microscope for sensitive samples.

Monolayer, Bilayer, Multilayer Graphene
After the preparation of graphene with either exfoliation or a chemical vapor process (CVD), the number and quality of the produced graphene layers need to be checked. Measure the number of layers with the contact free and substrate independent module for Total Interference Contrast with ZEISS Axio Imager 2 and detect holes in continuous layers. Profit from ZEISS GeminiSEM 500 when you need high resolution images of a number of graphene layers. Use its Energy selective Backscatter detector with its insensitivity to charging and acquire images of graphene at high resolution in a unique backscatter contrast. Determine the exact quantitative height with the in-situ AFM system.

Defects and Functional groups in Graphene
Before integration into a final device, defects in graphene are evaluated: carbon atoms can be sp3 -hybridized, functionalized, oxidized or missing. The chosen method here is Raman imaging, which, as a time consuming method, needs preselection of regions of interest. The in-situ Raman integrated into ZEISS GeminiSEM is the ideal tool for this purpose as the integration saves time in the workflow.

Integration in Electronic devices
Graphene has the potential to enhance the performance of electronic devices such as transistors and super capacitors. This is achieved by band gaps in graphene which are produced by creating thin ribbons. The narrower the bands, the higher the band gap.  The desired width of a graphene ribbon is less than 20 nm. The ZEISS Ion Microscope ORION NanoFab allows mask-less, contact-free, direct writing of patterns in graphene using a focused helium ion beam.

The outstanding resolution of the ion beam allows nano-structuring of graphene in the sub-10 nm range.

Integration in LEDs
Graphene functions as conductive back and/or front contact in LEDs. After the chemical vapor deposition of graphene on a substrate, the different expansion coefficients lead to wrinkles in graphene layers. In addition residues of PMMA (Polymethy methacrylate) remain on the surface of graphene after a transfer process. This can be partly healed by an annealing step. The quality influences the homogeneity of distribution and height of the semiconductor rods grown on top. The quality of the graphene front contact is in turn dependent on the semiconductor growth. Investigate the thin graphene layer on top of the semiconductor rods with high surface sensitivity using ZEISS ORION NanoFab.

Integration in Isolations
High-performance heat insulations are needed to improve energy efficiency in buildings. Freeze-casting suspensions of cellulose nano-fibres, graphene oxide and magnesium silicate (sepiolite) nano-rods are used for the production of super-insulating, fire-retardant foams. They perform better than traditional polymer-based insulating materials, are lighter and exhibit high thermal conductivities that are about half of that of expanded polystyrene. Find out more about pore orientation and density by a 3D reconstruction of the foam’s tubular pore structure with the ZEISS X-ray microscope Xradia Versa.

Integration in Batteries
The low electrical conductivities of sulfur in lithium sulfur batteries can be improved by using graphene as current collector. The intermediate polysulfide products and the final Li2S product affect the utilization of the active sulfur material and the rate capability of the battery. Meanwhile graphene functions as a reservoir and thus the polysulfide can be reused.
The volume change between sulfur and Li2S during charge/discharge induces stress in the electrode due to the different densities. It destroys its structural stability, which leads to rapid capacity decay. A sandwich of graphene on both sides of the sulfur electrode accommodates the large volumetric expansion. Verify and quantify these processes with a ZEISS X-ray microsope Xradia Versa.

Recommended Products for Graphene Research

ZEISS GeminiSEM

with Inlens EsB detector, AFM and Raman integration

GeminiSEM allows sub-nanometer resolution at low voltages ( 1.2 nm at 500 V) and high detection efficiency, thus revealing information about thin layers like monolayer graphene (335 pm). With 20 times greater Inlens detection signal, you will acquire crisp images of foldings within these layers. Seamlessly integrate AFM and Raman for height and detailed functional group determination.

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ZEISS Xradia Versa

Your Xradia Versa X-ray microscope non-destructively analyses graphene interfaces within the 3D volume of the final device. The sub-micron resolution reveals information about graphene layer homogeneity and e.g. changing properties of material due to graphene insertion.

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ZEISS ORION NanoFab

Your ORION NanoFab Ion Microscope is the tool of choice to create sub-10 nm structures in graphene for producing band gaps. The high surface sensitive technique enables imaging of highly transparent graphene sheets even on top of LED nano rods.

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