Graphene and 2D Materials Analysis with Imaging Ellipsometry

Imaging spectroscopic ellipsometry is a powerful tool for analysing graphene and other 2D materials. The Accurion nanofilm_ep4 is a versatile imaging ellipsometer for studying CVD grown, exfoliated and epitaxically grown flakes of 2D materials:

  • Localisation
  • Characterisation
  • Quality Control

Blue Scientific is the official distributor of imaging ellipsometry instruments from Accurion in the UK, Ireland and Nordic region. If you have any questions or if you’d like a quote, please get in touch:

Imaging ellipsometry systems

 Contact us on 01223 422 269 or info@blue-scientific.com


  

What Can You Study?

With imaging ellipsometry you can analyse these aspects of 2D materials – this list is not exhaustive, so if your area of interest is not mentioned, please get in touch:

  • Image monolayers on various substrates
  • Determine optical dispersion
  • Distinguish between mono-, bi- or n-layers
  • Automatic flake-search algorithm for identifying monolayers and well-defined thickness regions
  • Study hetero structures
  • Quality control: detect defects, impurities and special aspects of 2D nanoplates

2D materials brochure

Benefits of Imaging Ellipsometry

Imaging ellipsometry combines the strengths of two techniques:

  • Measurement quantities of ellipsometry
  • Lateral resolution of microscopy

The technique provides you with ellipsometric enhanced contrast micrographs, together with information about thickness and optical constants distribution.

Thickness measurements with an ellipsometer are highly accurate and, in the majority of cases, non-destructive. Optical constants can usually be determined independently.

Higher Lateral Resolution

Conventional ellipsometry uses a focused light spot to measure micro-sized structures. The lateral resolution is limited by the spot size, which can be as small as around 50 μm.

In contrast, imaging ellipsometry uses collimated light. This means that the lateral ellipsometric resolution is limited only by the objective and the CCD-camera used as a detector. This achieves a much greater lateral ellipsometric resolution down to 1 μm.

How Imaging Ellipsometry Works

Illumination arm on the left and analyser arm with the optical system at the right. The sample is placed on a motorised xy-table.

Analyse Materials on Different Substrates

The CCD-camera provides a live view of the sample. By rotating the polarising components, Delta (Δ) and Psi (Ψ) is measured at every pixel. The live view shows the progress and change in contrast at different polarisations.

You can select an area to measure on the contrast image in the live view. In conventional ellipsometry, the measured region is chosen by the position of the spot; in imaging ellipsometry it is selected in contrast view on the detector side. You can accurately select free-shaped regions of interest.

2D Materials Stacks

Select free-shaped regions of interest. Here a monolayer of MoS2 and a monolayer of WSe2 are arranged with an overlapping area of 2 μm x 6 μm. A) Ellipsometric contrast micrograph; b) Δ map; c) Ψ map. Courtesy of Ursula Wurstbauer, TU München.

This enables the use of knife edge illumination, which is a unique technique for measuring thin films on transparent substrates. With detector side selection and knife edge illumination, you can eliminate ghost images and disturbance from backside reflection.

The high contrast of ellipsometric enhanced contrast micrographs enables you to analyse different materials on different substrates. The polarising components of the system make this observation method more versatile and less substrate dependent.

Graphene on transparent substrates

2D materials can be measured on different substrates, including transparent substrates.
a) Monolayer of MoS2 on sapphire;
b) Monolayer of MoS2 on glass;
c) Graphene directly on Copper;
d) Hex BN on SiO2 (90 nm) | Si.

Further Information

The Accurion nanofilm_ep4 is extremely versatile. Further information about 2D materials applications is available in this brochure from Accurion. To discuss whether this technique would be suitable for your research, please get in touch.

Imaging ellipsometry systems

 Contact us on 01223 422 269 or info@blue-scientific.com

nanofilm_ep4 imaging ellipsometer

Accurion nanofilm_ep4 imaging ellipsometer