Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 51: 2D Materials: Session III (joint session DS/CPP/HL)

HL 51.2: Vortrag

Freitag, 16. März 2018, 10:00–10:15, H 2032

Chemical and optical properties of transition metal dichalcogenide monolayers at the nanometer and subnanometer scale — •Luiz Tizei1, Alberto Zobelli1, Ching-Hwa Ho2, Kazu Suenaga3, Alexandre Gloter1, Mathieu Kociak1, and Odile Stéphan11Laboratoire de Physique des Solides, University of Paris-Sud, CNRS, Orsay, France — 2National Taiwan University of Science and Technology, Taipei, Taiwan — 3AIST, Tsukuba, Ibaraki, Japan

Defects and interface play an important role in material properties. Therefore, their characterization at the nanometer scale is crucial. Here, core-loss EELS and high angle annular dark field imaging have been used to identify single Cr atoms in WSe2 monolayers. These atoms are always located at the metal site (W) with a 3+ formal valence, as deduced from EELS fine structure comparison with known references and X-ray photoelectron spectroscopy (XPS). Furthermore, Cr atoms are observed systematically close to single our double Se vacancies, indicating a possible electron doping of the system. Moreover, semiconducting 2H phase TMD monolayers present spin-split valence and conduction bands due to spin-orbit coupling. These two near band edge states are separated by from a few tens to a few hundred meV and can be measured by EELS with high spatial resolution. As an example, we will show measurements of the near band edge losses as a function of position across an interface between two TMDs. Results will be compared to calculated loss functions, tacking into account the materials’ dielectric function.

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