(a) Large scale STM topograph of MoS2 islands on fully covered Gr/Ir(1 1 1) grown in two successive growth cycles and subsequently imaged in situ. The inset shows a zoomed in part of the image marked with a blue box. The arrows in the inset mark different features of the topograph. Green: monolayer MoS2 island, black: bilayer MoS2 island, white: mirror twin boundary, blue: metallic edge state. Image information: tunneling voltage -1.5 V, tunneling current 20 pA, image size 250 × 250 nm2. (b) Corresponding LEED pattern at 86 eV. (c) XPS spectra of the Mo 3d peak. The doublet peak is split into Mo 3d5/2 and Mo 3d3/2 components. The red color traces show the peak for elemental Mo, green color for MoS2 which is shifted by 0.95 eV to a higher binding energy. The additional peak in the green spectrum around 226.5 eV binding energy is due to the S 2s core level. The spectra were recorded using an excitation energy of 370 eV. (d) S 2p doublet.
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