RESONANT PHOTOELECTRON-SPECTROSCOPY AT THE MO 4P-]4D ABSORPTION-EDGE IN MOS2

A systematic study has been conducted of the resonant behavior of the valence-band photoelectron spectrum of MoS2 for hv = 26-70 eV, spanning the Mo 4p --> 4d transition region. A broad Fano-like resonance appears at approximately 42 eV in the constant-initial-state (CIS) intensity plot of the d(z)2 peak near the valence-band maximum [approximately 2 eV binding energy (BE)], confirming its predominantly Mo 4d character. A second shoulder on the higher-hv side of the maximum in the d(z)2 CIS intensity plot is suggested to result from transitions to unoccupied states in the 5sp band approximately 10 eV above E(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 d(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 approximately 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.