Compositional change of (0001) WS₂ surfaces induced by ion beam bombardment with energies between 100 and 1500 eV

Ion beam bombardment at low ion energies is of interest in both surface analysis and thin film deposition, however, concerns exist regarding preferential sputtering and chemical reduction at the surface. In this study, the rate of reduction and extent of alteration of (0001) WS₂ was examined with respect to type of ion beam (Ne⁺, Ar⁺, and Kr⁺), incident ion energy and ion beam dosage using x‐ray photoelectron spectroscopy. At saturation, the surface stoichiometry was reduced to approximately WS_0.4, in general agreement with preferential sputtering models. By decreasing the atomic mass of the ion or the energy of the ion beam, the resolution of the surface species formed was enhanced. With ion bombardment, the W(4f) spectrum shows the formation of a reduced W species representing metallic W. In addition, the enhanced W concentration at the surface causes an increased density of states up to the Fermi level as well as a 0.5 eV band bending due to pinning at surface defects. The corresponding S(2p) spectrum shows the formation of a reduced S species. This reduced S species is associated with S surrounded by metallic W, which causes a final state polarization effect, decreasing the binding energy.