Effects of Defects on Band Structure and Excitons in WS₂ Revealed by Nanoscale Photoemission Spectroscopy

Abstract

Two-dimensional materials with engineered composition and structure will provide designer materials beyond conventional semiconductors. However, the potentials of defect engineering remain largely untapped, because it hinges on a precise understanding of electronic structure and excitonic properties, which are not yet predictable by theory alone. Here, we utilize correlative, nanoscale photoemission spectroscopy to visualize how local introduction of defects modifies electronic and excitonic properties of two-dimensional materials at the nanoscale. As a model system, we study chemical vapor deposition grown monolayer WS2, a prototypical, direct gap, two-dimensional semiconductor. By cross-correlating nanoscale angle resolved photoemission

Synthesis and characterization of WS2/graphene/SiC van der Waals heterostructures via WO3−x thin film sulfurization

“…The spectra show the valence band edge of WS 2 superimposed on the continuum of states down to the Fermi level contributed by the graphene layer. The position of VBM for WS 2 is located at 1.38 eV below the Fermi level and is consistent with the observed VBM for sulfur-deficient edges in monolayer WS 2 (1.35 eV) 44 . Previous reports have placed the VBM for WS 2 on graphene/SiC between 1.13 eV and 1.84 eV below the Fermi level 27,28,43 .…”

Computational framework chinook for angle-resolved photoemission spectroscopy

“…At the bottom of the band, the dipole selection rules suppress photoemission intensity from even the main band. In the disorder-averaged supercell, a substantial broadening of the spectral lineshape is observed [38,39]. As indicated by the overlain bandstructures of Fig.…”

Toward Valley‐Coupled Spin Qubits

“…ARPES studies on the electronic properties on TMDC layered materials typically involved small size (≈micrometer) TMDC flakes obtained by direct exfoliation from single bulk crystal and then transferred onto a conductive substrate. [ 65–69 ] Band structure investigations were therefore mainly conducted by micro‐ARPES techniques at synchrotron radiation facilities where the reduced photon beam size (≈micrometer) combined with microscopy techniques can be achieved to allow an accurate selection of the probed micrometer‐size flakes. This technique was successfully employed in mapping the electronic band dispersion of TMDCs exfoliated layer of various thicknesses revealing, for example, the change of the valence band maximum position in the reciprocal space from K to Γ point and the increase of band branches near Γ when the layer thickness increases from monolayer to multilayer ( Figure 4a,b).…”

“…This technique was successfully employed in mapping the electronic band dispersion of TMDCs exfoliated layer of various thicknesses revealing, for example, the change of the valence band maximum position in the reciprocal space from K to Γ point and the increase of band branches near Γ when the layer thickness increases from monolayer to multilayer ( Figure 4a,b). [ 65–69 ]…”