Abstract
Generally, the lack of long-range order in materials prevents from experimentally addressing their electronic band dispersion by angle-resolved photoelectron spectroscopy (ARPES), limiting such assessment to single crystalline samples. Here we demonstrate that the ARPES spectra of azimuthally disordered transition metal dichalcogenide (TMDC) monolayers with 2 H phase are dominated by their band dispersion along the two high symmetry directions Γ-K and Γ-M. We exemplify this by analyzing the ARPES spectra of four prototypical TMDCs within a mathematical framework, which allows to consistently explain the reported observations. A robust base for investigating TMDC monolayers significantly beyond single crystal samples is thus established.
Highlights
The lack of long-range order in materials prevents from experimentally addressing their electronic band dispersion by angle-resolved photoelectron spectroscopy (ARPES), limiting such assessment to single crystalline samples
Sufficiently large single crystalline samples are required for conventional angle-resolved photoemission spectroscopy (ARPES) measurements, which is still challenging for transition metal dichalcogenide (TMDC) monolayers and limits obtaining the desired information on the electronic band structure for many interesting systems
With highresolution ARPES spectra of single crystalline and azimuthally disordered WSe2 monolayers we reveal the impact of the azimuthal disorder and rationalize that the two high-symmetry directions [Γ-K and Γ-M of the Brillouin zone (BZ)] dominate the ARPES spectra of azimuthally disordered samples
Summary
The lack of long-range order in materials prevents from experimentally addressing their electronic band dispersion by angle-resolved photoelectron spectroscopy (ARPES), limiting such assessment to single crystalline samples. We propose an alternative explanation for the observed dispersing bands in ARPES of 2D powders, without the need of using the concept of quasi 1D-DOS and Van Hove singularities In this contribution, we evidence high-symmetry induced sharp dispersion for TMDC monolayer samples with azimuthally disordered flakes by ARPES measurements and we consolidate our observations with the help of density functional theory (DFT) calculations and angular averaging considerations. With highresolution ARPES spectra of single crystalline and azimuthally disordered WSe2 monolayers we reveal the impact of the azimuthal disorder and rationalize that the two high-symmetry directions [Γ-K and Γ-M of the Brillouin zone (BZ)] dominate the ARPES spectra of azimuthally disordered samples This is a consequence of the angular integration of the single crystal TMDC monolayer band structure. The same is evidenced for three further prototypical semiconducting TMDCs (MoS2, MoSe2, and WS2), allowing the experimental determination of band dispersion in the two most important BZ directions for azimuthally disordered TMDC monolayers
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