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O: Fachverband Oberflächenphysik

O 58: 2D materials beyond graphene: TMDCs, silicene and relatives II

O 58.8: Vortrag

Mittwoch, 14. März 2018, 12:15–12:30, MA 043

Observing structural information of TMDCs with FM-AFM in ambient and UHV — •Korbinian Pürckhauer, Dominik Kirpal, Leo Waldhauser, Alfred J. Weymouth, and Franz Giessibl — University of Regensburg, Regensburg, Germany

The development in nanoelectronics demands reducing the size of its elements which led to an increase of interest in TMDCs. These show a range of interesting properties like a band gap in the range of Si and GaAs and allow high on/off switching ratios for FETs.

We studied bulk MoS₂, WS₂, MoSe₂ and WSe₂ cleaved in air with a qPlus AFM. The high stiffness (k>1 kN) of the qPlus sensor allows us to operate in the frequency-modulation mode with sub-Angstrom amplitudes. On all surfaces we were able to observe atomic resolution in ambient conditions. The spacing between steps on MoS₂ and WS₂ were very large (at least hundreds of nm). In contrast, the MoSe₂ and WSe₂ surfaces appeared to be contaminated directly after cleavage. Both surfaces were covered with particles that were approximately 10 nm high. These particles were not observed on the MoS₂ and WS₂ surfaces. Transferring MoSe₂ into vacuum and annealing at 700^∘C resulted in a cleaner surface. This suggests that TMDCs with Sulfur as a chalcogen atom are more suitable for devices made in ambient conditions.