Resonant photoelectron spectroscopy at the Mo 4p→4dabsorption edge inMoS2

A systematic study has been conducted of the resonant behavior of the valence-band photoelectron spectrum of ${\mathrm{MoS}}_2$ for hν=26–70 eV, spanning the Mo 4p→4d transition region. A broad Fano-like resonance appears at ∼42 eV in the constant-initial-state (CIS) intensity plot of the ${\mathit{d}}_{\mathit{z}}^2$ peak near the valence-band maximum [∼2 eV binding energy (BE)], confirming its predominantly Mo 4d character. A second shoulder on the higher-hν side of the maximum in the ${\mathit{d}}_{\mathit{z}}^2$ CIS intensity plot is suggested to result from transitions to unoccupied states in the 5sp band ∼10 eV above ${\mathit{E}}_{\mathit{F}}$, by comparison with a partial-yield spectrum and previous inverse-photoemission data. The region of the valence band in the range 3–4.5-eV BE also exhibits resonant behavior, indicating Mo 4d character, although somewhat less than for the ${\mathit{d}}_{\mathit{z}}^2$ peak. The 5–7-eV BE range does not exhibit resonance behavior at the Mo 4p edge and, therefore, contains negligible Mo 4d character. A feature at ∼30 eV in the CIS intensity plot for the 5–7-eV BE range could not be definitively assigned in this study, but may be due to a resonance between direct photoemission and a process involving absorption and autoionization of electronic states that contain Mo 5s and 5p character.