Directional charge delocalization dynamics in semiconducting 2H-MoS[Formula: see text] and metallic 1T-Li[Formula: see text]MoS[Formula: see text]

Robert Haverkamp; Nomi L A N Sorgenfrei; Erika Giangrisostomi; Stefan Neppl; Danilo Kühn; Alexander Föhlisch

doi:10.1038/s41598-021-86364-2

Directional charge delocalization dynamics in semiconducting 2H-MoS[Formula: see text] and metallic 1T-Li[Formula: see text]MoS[Formula: see text]

Sci Rep. 2021 Mar 25;11(1):6893. doi: 10.1038/s41598-021-86364-2.

Authors

Robert Haverkamp^{1

2}, Nomi L A N Sorgenfrei¹, Erika Giangrisostomi¹, Stefan Neppl¹, Danilo Kühn¹, Alexander Föhlisch^{1

2}

Affiliations

¹ Methods and Instrumentation for Synchrotron Radiation Research PS-ISRR, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
² Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany.

Abstract

The layered dichalcogenide MoS[Formula: see text] is relevant for electrochemical Li adsorption/intercalation, in the course of which the material undergoes a concomitant structural phase transition from semiconducting 2H-MoS[Formula: see text] to metallic 1T-Li[Formula: see text]MoS[Formula: see text]. With the core hole clock approach at the S L[Formula: see text] X-ray absorption edge we quantify the ultrafast directional charge transfer of excited S3p electrons in-plane ([Formula: see text]) and out-of-plane ([Formula: see text]) for 2H-MoS[Formula: see text] as [Formula: see text] fs and [Formula: see text] fs and for 1T-Li[Formula: see text]MoS[Formula: see text] as [Formula: see text] fs and [Formula: see text] fs. The isotropic charge delocalization of S3p electrons in the semiconducting 2H phase within the S-Mo-S sheets is assigned to the specific symmetry of the Mo-S bonding arrangement. Formation of 1T-Li[Formula: see text]MoS[Formula: see text] by lithiation accelerates the in-plane charge transfer by a factor of [Formula: see text] due to electron injection to the Mo-S covalent bonds and concomitant structural repositioning of S atoms within the S-Mo-S sheets. For excitation into out-of-plane orbitals, an accelerated charge transfer by a factor of [Formula: see text] upon lithiation occurs due to S-Li coupling.