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O: Fachverband Oberflächenphysik
O 58: 2D materials beyond graphene: TMDCs, silicene and relatives II
O 58.8: Talk
Wednesday, March 14, 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.