Initial- and final-states effects in the conduction bands of 2H-MoS2(0001) studied by k//-resolved inverse photoemission spectroscopy

The conduction-band structure of the lamellar semiconductor molybdenum disulfide MoS2(0001) has been studied by k∥-resolved inverse photoemission spectroscopy (KRIPES) along two major symmetry directions (M¯′Γ¯ M¯ and K¯′Γ¯ K¯) of the surface Brillouin zone. Among the three observed features, the lowest-energy one (A) is attributed to antibonding combinations of Mo 4d and S 3p states. After decomposition, the experimental dispersion of its individual components is compared with theoretical band-structure calculations. An overall agreement is found with three calculations, except for a dispersionless shoulder observed just above the Fermi level near the Γ¯ point. This peak is interpreted as resulting from a narrow impurity band. The relatively high intensity of the A features is explained by a resonant optical transition with initial states found at 9.5 eV above the Fermi level, which are also detected in the modulations of the target current. Moreover, from both KRIPES and target current measurements, the intensity of the various A components is observed to behave differently along the two equivalent but opposite azimuths Γ¯M¯ and Γ¯ M¯′. This reflects the asymmetric atomic arrangement of MoS2 in this direction.