SALES - Information SERVICE - Information
Marcus Liemen - Business Development Accurion

Marcus Liemen

Business Development

Phone:

Mail: ml@accurion.com

Dr. Peter Thiesen - Senior Application Specialist Accurion

Dr. Peter Thiesen

Senior Application Specialist

Phone: +49-551-9996020

Mail: pt@accurion.com

Daniela Bogner - Sales Manager Accurion

Daniela Bogner

Sales Manager

Phone: +49-551-9996013

Mail: db@accurion.com

Linda Thieme - Sales Manager Accurion

Linda Thieme

Sales Manager

Phone: +49-551-9996016

Mail: lth@accurion.com

Sebastian Funke - Application Specialist, 2D Materials Accurion

Sebastian Funke

Application Specialist, 2D Materials

Phone: +49-551-999600

Mail: sfu@accurion.com

Dr. Christian Hoffmann - Application Specialist for Biological Applications Accurion

Dr. Christian Hoffmann

Application Specialist for Biological Applications

Phone: +49-551-9996021

Mail: cho@accurion.com

Stephan Ferneding - Chief Executive Officer Accurion

Stephan Ferneding

Chief Executive Officer

Phone: +49-551-999600

Mail:

Narayana Sharma - Sales and Application Accurion

Narayana Sharma

Sales and Application

Phone: +91-98450 04273

Mail: sharma@accurion.com

Frank Zuo - Sales and Application Accurion

Frank Zuo

Sales and Application

Phone: +86-21 5017 9099

Mail: fz@accurion.cn

Dr. Antonio Gonzalez - Service and LB-Application Specialist Accurion

Dr. Antonio Gonzalez

Service and LB-Application Specialist

Phone: +49-551-9996035

Mail: ago@accurion.com

Arash Mirhamed - Product Manager Accurion

Arash Mirhamed

Product Manager

Phone: +49-551-9996015

Mail: am@accurion.com

Holger Grube - Service Engineer Accurion

Holger Grube

Service Engineer

Phone: +49-551-9996023

Mail: service-halcyonics@accurion.com

SALES / SUPPORT
Logo

Graphene

Compendium: Application of Imaging Ellipsometry - Graphene and 2D Materials

Imaging spectroscopic ellipsometry is applied to characterize graphene and other 2D materials. CVD grown, exfoliated and epitaxically grown flakes of 2D materials are investigated with the imaging ellipsometer nanofilm_ep4. This compendium addresses the following topics:
• Imaging of monolayers on different substrates
• Determination of the optical dispersion
• Distinction between mono-, bi- or n-layers
• Automatic flakesearch algorithm for identification of monolayers or well-defined thickness regions
• Exploration of hetero structures
• Quality control by detecting defects and special aspects of 2D nanoplates

Hetero-Structure MoS2/WSe2 investigated by Imaging Ellipsometry 

2D-materials often show superior properties compared to their bulk or few-layer materials. The stacking of different mono layered materials do even promise more interesting combinations. MoS2 and WSe2 show strong excitonic dominated behaviour. In theory, the stacking shows the opportunity of intra-layer excitons.

Application Note - Automatic Localization of Mono- to N-Layers of 2D Materials by Spectroscopic Imaging Ellipsometry

In   this   application   note   we   present   the   capability   of   imaging   spectroscopic ellipsometry to automatically localize small flakes down to a few microns in lateral dimension and to distinguish between mono-, bi- or n-layers. The method is based on  the  pixel-wise  comparison  of  a  stack  of  delta  and  psi  maps  with  the  optical model.  In  general,  it  offers  the  opportunity  to  identify  areas  of  a  sample  with defined layer thickness or optical properties. For demonstration purposes, a sample with a graphene flake in-between a number of thicker layers and one with a number of exfoliated Molybdenum disulfide flakes are presented.

Graphene and graphene oxide

Carbon at interfaces: Graphene, graphen oxide, carbon nanotubes and fullerene derivatives
Graphene on SiO2|Si: profile Delta map at 440 nm, AOI = 60 °, 10 x objective

Graphene is a one-atom-thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. The term graphene was coined as a combination of graphite and the suffix -ene by Hanns-Peter Boehm, who described single-layer carbon foils in 1962. Graphene is the basic structural element of some carbon allotropes including graphite, charcoal, carbon nanotubes, and fullerenes. It can also be considered as an indefinitely large aromatic molecule, the limiting case of the family of flat polycyclic aromatic hydrocarbons.

 

With imaging ellipsometry, graphene flakes can easilier be located than with an AFM. Single- and double layer flakes can be destinguished. The Nobel Prize in Physics for 2010 was awarded to Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene".

Characterization of graphene through imaging spectroscopic ellipsometry (Poster, 2013)

Characterization of graphene through imaging spectroscopic ellipsometry

Based on new developments, spectra with higher spectral resolu-tion are available in the NIR up to 1700 nm. For wavelength above 1000 nm an InGaAs cooled FPA detector was included.
Delta- and Psi maps of a graphene flake are recorded and show signif-icant different behavior than the substrate. The technique is promis-ing to obtain information about Drude adsorption with a lateral res-olution of few micro meters. It will improve the understanding of the dielectrical properties of graphene and of the graphene substrate in-teractions

 

Reference:

Thiesen P.H. (2013) Imaging NIR-Ellipsometry of Graphene. 27th Conference of the European Colloid and Interface Society, September 1- 6, Sofia, Bulgaria

 

Spectroscopic imaging ellipsometry and Fano resonance modeling of graphene (Literature, 2012)

Ellipsometric contrast micrograph of graphene flakes on SiO2|Si substrate
Ellipsometric contrast micrograph of graphene flakes at SiO2|Si substrate.

Matković et al. have examined the optical properties of exfoliated graphene on an Si/SiO2 substrate using spectroscopic imaging ellipsometry in the visible range (360–800 nm). Measured spectra were analyzed by an optical model based on the Fresnel coefficient equations. The optical model was supported by correlated Raman and atomic force microscopy measurements. The complex refractive index of graphene was obtained by inversion of the measured ellipsometry data. The Fano line-shape was used to parameterize the optical properties. Measurements were highly reliable due to the numerous advantages of the spectroscopic imaging ellipsometric technique combined with the proper choice of substrate and experimental set-up. Thickness maps of the graphene sample were obtained from spatially resolved imaging ellipsometry spectra with a spot size of 1 μm. The data showed the presence of a water layer on the surface of the sample, and the thickness was mapped showing the distribution of water over graphene in ambient conditions.

 

Reference:

Matković A, Beltaos A., Milićević M., Ralević U., Vasić B., Jovanović D., Gajić R. (2012) J. Appl. Phys. 112, 123523.

(Download)

 

High resolution imaging of few-layer graphene (Literature, 2012)

Albrektsen et al. successfully demonstrate how imaging ellipsometry can be applied to obtain high-resolution thickness maps of few-layer graphene (FLG) samples, with the results being thoroughly validated in a comparative study using several complementary techniques. The thickness map, revealing distinct terraces separated by steps corresponding to mono- and bilayers of graphene, is extracted from a pixel-to-pixel fitting of ellipsometric spectra using optical constants (n = 2.7 and k = 1.2) derived by fitting slab model calculations to averaged Ψ and Δ spectra collected in large homogenous sample areas. An analysis of reflection spectra and contrast images acquired by ORM confirm the results by quantifying the number of graphene layers and retrieving the FLG optical constants using a simple Fresnel-law-based slab model. The morphology results are further corroborated with AFM and Raman images, the latter unambiguously verifying that the thinnest part of the FLG consists of a graphene bilayer and providing additional information of electronic origin that might help identifying subtle FLG features, such as the presence of impurities, variations in stacking order, or rolling and folding at the FLG edges.

 

Reference:

Albrektsen O., Eriksen R.L., Novikov S.M:, Schall D., Karl M., Bozhevolnyi S.I., Simonsen A. C. (2012) High resolution imaging of few-layer graphene. J. Appl. Phys. 111, 064305.

(Download)

 

Imaging ellipsometry of graphene (Literature, 2010)

Imaging ellipsometry of graphene
Psi map of the graphene flake characterized by Wurstbauer et al.

Wurstbauer et al. [2010] present Imaging ellipsometry studies of graphene on SiO2/Si and crystalline GaAs. They demonstrate that imaging ellipsometry is a powerful tool to detect and characterize graphene on any flat substrate. Variable angle spectroscopic ellipsometry is used to explore the dispersion of the optical constants of graphene in the visible range with high lateral resolution. In this way the influence of the substrate on graphene’s optical properties can be investigated.

 

References:

Wurstbauer U., Röling Ch., Wurstbauer U, Wegscheider W, Vaupel M., Thiesen P.H., Weiss D. (2010) Imaging ellipsometry of graphene. ApplPhysLett_97_231901

more details

Localization and Characterization of Graphene Crystallites (Poster, 2010)

Localization and Characterization of Graphene Crystallites

Reference: 

  1. P.H. Thiesen, C. Röling (2010) Localization and characterization of graphene crystallites by using spectroscopic variable angle imaging ellipsometry.109. Hauptversammlung der Deutschen Bunsen-Gesellschaft für Physikalische Chemie e.V., 13. - 15. Mai 2010, Bielefeld, Germany

Thiesen P.H. (2013) Imaging NIR-Ellipsometry of Graphene. 27th Conference of the European Colloid and Interface Society, September 1- 6, Sofia, BulgariaLocalization
and Characterization of Graphene CrystallitesBased on new developments, spectra with higher spectral resolu-tion are available in the NIR up to 1700 nm. For wavelength above 1000 nm an InGaAs cooled FPA detector was included.
Delta- and Psi maps of a graphene flake are recorded and show signif-icant different behavior than the substrate. The technique is promis-ing to obtain information about Drude adsorption with a lateral res-olution of few micro meters. It will improve the understanding of the dielectrical properties of graphene and of the graphene substrate in-teractions

Graphene and graphene oxide (Application note)

Graphene and graphene oxide

Graphene and graphene oxide layers are localized and charcterized on different substrate materials by means of the spectroscopic imaging ellipsometer nanofilm ep3se. The thickness and the dispersion functions of the refractive index n and of the extinction k of a few μm-wide layers are obtained. The results of imaging ellipsometry agree with the results obtained by the combination of AFM and confocal microscopy within the error margins. By contrast to the latter methods the measurement time is much shorter with imaging ellipsometry.
 

Characterization of Thermally Reduced Graphene Oxide by Imaging Ellipsometry (Literature, 2008)

Jung et al. (2008) measured the dispersion functions for the refractive index and the extinction coefficient of single- and multiple-layer graphene oxide samples by imaging spectroscopic ellipsometry in the wavelength range of 350-1000 nm and were compared to previously reported results measured by confocal microscopy. The dispersion functions for thin platelets were also compared to those obtained by standard spectroscopic ellipsometry on a deposit consisting of many overlapping graphene oxide layers. Changes were observed in both the thickness of the deposits and the values of the dispersion parameters following heating. A model is proposed to explain these observations, based on the removal of water between the graphene-oxide layers upon thermal treatment.

 

References:

Jung I., Vaupel M., Pelton M., Piner R., Dikin D.A., Stankovich S., An J., Ruoff R. (2008)

Characterization of Thermally Reduced Graphene Oxide by Imaging Ellipsometry. Journal of Physical Chemistry 112, 8499-8506
more details

 

 

CONTACT
© Accurion GmbH 2018