AVS 62nd International Symposium & Exhibition
    2D Materials Focus Topic Tuesday Sessions
       Session 2D+EM+NS+SS+TF-TuM

Paper 2D+EM+NS+SS+TF-TuM11
Determining the Optical Properties of Exfoliated 2D Molybdenum Disulfide on Various Substrates with Imaging Spectroscopic Ellipsometry

Tuesday, October 20, 2015, 11:20 am, Room 212C

Session: Optical and Optoelectronic Properties of 2D Materials
Presenter: Peter H. Thiesen, Accurion GmbH, Germany
Authors: P.H. Thiesen, Accurion GmbH, Germany
S. Funke, HAWK, Germany
B. Miller, TU München, Germany
E. Parzinger, TU München, Germany
G. Hearn, Accurion Inc.
A.W. Holleitner, TU München, Germany
U. Wurstbauer, TU München, Germany
Correspondent: Click to Email
Ellipsometry is a non-destructive optical method for determining film thickness and optical properties. It measures the change in the state of polarization of the light reflected from the film interfaces. Imaging ellipsometry, which combines the power of ellipsometry with microscopy, has overcome the limitation of poor sample lateral resolution found in conventional non-imaging ellipsometers. The enhanced spatial resolution of imaging ellipsometers potentially expands ellipsometry into new areas of microanalysis, microelectronics, and bio analytics.

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Molybdenum disulfide is a layered transition metal dichalcogenide. From the point of current research, 2D-nano materials based on MoS2 are very promising because of the special semiconducting properties. The bulk material has an indirect 1.2 eV electronic bandgap, but single layer MoS2 has a direct 1.8 eV bandgap. The monolayer can be used in prospective electronic devices like transistors (MOSFETs) or photo detectors.

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Wavelength spectra of ellipsometric parameters Delta and Psi of the MoS2 monolayers and multilayers were recorded as well as microscopic maps. In case of Sapphire, The psi maps at wavelength of higher energies than the bandgap show a clear contrast between the monolayer and the substrate and at lower energies there is no contrast between the monolayer and the substrate, but the multilayer areas still show a clear contrast-making the unique properties of MoS2 monolayers directly visible. The advantage of imaging ellipsometry is the visualisation of the shape of the monolayer and the opportunity to classify the homogenity of the optical properties of the microcrystallite. To quantify the optical properties, different approaches of optical modelling will be discussed.