Mainz 2017 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 35: Laser Development and Applications (Spectroscopy)

Q 35.6: Talk

Wednesday, March 8, 2017, 15:45–16:00, P 5

Spatial Nonuniformity and Photochemical Doping in exfoliated WS2 Monolayers — •Ioannis Paradisanos — N. Plastira 100, Heraklion, Crete, Greece

Monolayers of transition metal dichalcogenides (TMDs) are promising new materials for future 2D nanoelectronic systems. With their tunable direct gap in the visible range of the optical spectrum and high surface-to-volume ratio, these 2D semiconducting systems are ideal for field-effect transistors, photovoltaics, light-emitting diodes, single-atom storage, molecule sensing and quantum-state metamaterials.

Here we report on the extraordinary photoluminescence (PL) and Raman properties, not only of the physical but also of intentionally created via femtosecond laser ablation, boundaries of mechanically exfoliated WS2 monolayers. In particular, it is shown that the edges of such monolayers exhibit significant Raman shifts as well as remarkably increased PL efficiency compared to their respective central area with the emission channels being of different origin. Moreover, by exploiting the interaction of UV nanosecond pulses with WS2 monolayers in rich Cl2 environment, a fine control of the crystal*s carrier density can be achieved. This is confirmed by micro-PL measurements at 78K that show significant energy shifts of the neutral and charged exciton*s emission. At the same time, micro-Raman experiments reveal systematic shifts of the -doping sensitive- A1* vibrational mode.

We envisage that these novel findings could find diverse applications in the development of TMDs-based optoelectronic devices.