Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

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

HL 51.2: Talk

Friday, March 16, 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 Stéphan¹ — ¹Laboratoire 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.