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Foto (Matthias Groppe): Holographie-Apparatur von Herrn Dr. Andreas Redler

Foto: Foto (Matthias Groppe): Holographie-Apparatur von Herrn Dr. Andreas Redler

Donnerstag, 11.01.2018 | 16.15 - 17.00 Uhr | Hörsaal A1

Semiconducting 2D crystals and their heterostructures

Dr. Ursula Wurstbauer

WSI - Technische Universität München

The (re-)discovery of graphene in 2004 by Geim and Novoselov [1] was hour of birth to the vibrant interdisciplinary research area of 2D materials. Any van-der Waals layered material can be split into single- and few layers with often superior characteristics compared to the three dimensional crystal. The talk will mainly focus on transition metal dichalcogenides (TMDs) [2], where a monolayer consists of a transition metal surrounded by two chalcogen atoms. Semiconducting TMDs such as MoS2 or WSe2 are of current interest for optoelectronic, sensing and energy harvesting applications, but also for studying fundamental aspects of light-matter interaction dominated by a high exciton binding energy in the order of 500 meV [2].

TMDs provide a high sun light absorbance of up to 15% in the monolayer limit, photocatalytic stability, HER activity, strong photocurrent response, environmental sensing capabilities [3-7]. I will discuss the robustness of the fascinating spin- and valley properties against defects induced by a focused helium ion beam and introduce Raman measurements as a versatile, non-destructive and contactless probe to particularly study charge carrier density, defect concentration and strain [2-8].

In the last part of the talk, I will discuss van der Waals heterostructures - a novel platform for tailored heterostructures without the limitations of lattice mismatch. We have recently demonstrated that MoSe2/WSe2 monolayers host long-lived momentum direct and indirect interlayer excitons making those structures an interesting material system to study many-body phenomena of composite bosons at elevated temperatures [9].

We acknowledge support by BaCaTeC and DFG via cluster of excellence “Nanosystems Initiative Munich (NIM)”, and DFG project “WU 637/4-1”.

[1] K. S. Novoselov, A. K. Geim et al., Science 306, 666 (2014).
[2] U. Wurstbauer et al., J. Phys. D: Appl. Phys. 50 (2017) 173001.
[3] S. Funke, UW et al., J. Phys. Condens. Matter 28, 385301 (2016).
[4] E. Parzinger, UW et al., ACS Nano 9(11), 11302 - 11309 (2015).
[5] E. Parzinger, UW et al., Appl. Mat. Today, doi/10.1016/j.apmt.2017.04.007 (2017).
[6] E. Parzinger, UW et al., arXiv 1708.00250 (2017).
[7] B. Miller, UW et al., Appl. Phys. Lett. 106, 122103 (2015).
[8] J. Klein, UW, et al., arxiv:1705.01375 (2017).
[9] B. Miller, UW, et al. Nano Lett., doi:10.1021/acs.nanolett.7b01304 (2017).

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