Inhomogeneity of Cleaved Bulk MoS2 and Compensation of Its Charge Imbalances by Room‐Temperature Hydrogen Treatment

Abstract Synthetic single crystals of bulk molybdenum disulphide cleaved in ultrahigh vacuum are mapped across a large (≈25 mm2) area by X‐ray photoelectron spectroscopy, both statically and transiently following above‐bandgap excitation by an ultrafast laser. This work finds that: I) A cleaved surface typically displays spatially inhomogeneous properties, manifested by large (≈1 eV) variations in binding energy and band bending and variable degrees of stability of those over time as a result of variable gas uptakes from the residual atmosphere. II) Moderate (350 °C) annealing and exposure to molecular hydrogen can be cycled to switch between smaller and larger surface band bending, the switch being reversible but strongly sample‐position dependent. III) Upon exposure to atomic hydrogen, the binding energy of the entire surface levels out to a common (within