Electronic band structure of single-crystal and single-layer WS2: Influence of interlayer van der Waals interactions - art. no. 205416

The valence band structure of the layered transition metal dichalcogenide W S2 has been determined experimentally by angle resolved photoelectron spect roscopy and theoretically by augmented spherical wave band structure calcul ations as based on density functional theory. Good agreement between experi mental and calculated band structure is observed for single crystal WS2. An experimental band structure of a single layer was determined from an elect ronically decoupled film prepared on a single crystalline graphite substrat e by metalorganic van der Waals epitaxy. The polarization dependent photoem ission selection rules of the single layer film are appropriate for a free standing film. The experimental single layer band structure shows some diff erences compared to band structure calculations using bulk atomic positions within the layer. We conclude that relaxation of the single layer occurs a s a consequence of the missing interlayer interactions leading to close agr eement between electronic structure of the single layer and single crystal. As a consequence of the missing interlayer interactions the valence band m aximum for the single layer is located at the K point of the Brillouin zone .