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O: Fachverband Oberflächenphysik
O 53: Graphene IV
O 53.7: Talk
Wednesday, March 28, 2012, 18:15–18:30, MA 041
Phonons in single-layer and few-layer MoS2 — •Alejandro Molina-Sanchez and Ludger Wirtz — Institute for Electronics, Microelectronics, and Nanotechnology (IEMN), Lille, France
In recent experiments, the single-layer dichalcogenide MoS2 has exhibited a direct band-gap of 1.75 eV and a electron mobility close to that of graphene, becoming an appealing material in the area of optoelectronic devices [1].
Recent Raman measurements have revealed unexpected trends in the vibrational properties of MoS2 when the number of layers changes, as a frequency decreasing of the phonon mode E2g1 with increasing numbers of layers, that contradicts the expectation that the weak interlayer forces between neighbour layers should increase the effective restoring forces acting on atoms [2].
The purpose of our work is the clarification of this issue by a detailed ab initio study of the phonons, and comparing afterwards with experimental results. We explain this decrease by an enhancement of the dielectric screening of the long-range Coulomb interaction between the effective charges with a growing number of layers [3].
[1] B. Radisavljevic et. al., Nat. Nano. 6, 147 (2011). [2] C. Lee et. al., ACS Nano 4 2695 (2010). [3] A. Molina-Sanchez and L. Wirtz, Phys. Rev. 84, 155413 (2011).