Resonance Photoelectron Spectroscopy of the MoS2 Conduction Band using Alkali Metal Intercalation

Recent valence band photoelectron spectroscopy (PES) studies of the semiconducting transition metal dichalcogenides (TMDs) MoS₂ and WS₂ after alkali metals were deposited on their surfaces provide indirect evidence of charge transfer to the TMD conduction band via the rigid band model. To provide more direct evidence, we conducted a synchrotron PES study of the MoS₂ (0001) surface after deposition of K. For low dosages, K was adsorbed on the MoS₂ (0001) surface; increasing dosages resulted in intercalation. Resonant PES data were taken of K/MoS₂ (0001) for hν= 30-70 eV, spanning the Mo 4p-4d transition region, similar to a previous study of pure MoS_2.(J.R. Lince, S.V. Didziulis, J.A. Yarmoff, Phys Rev B 43(6) (1991) 4641.) A strong Fano-like resonance in the region above the VBM provided direct evidence of electron transfer to the MoS₂ conduction band during adsorption/intercalation, and shows that the bottom of the MoS₂ conduction band contains considerabl e Mo 4d character.