Polarized X-ray absorption spectra and electronic structure of molybdenite (2H-MoS2)

Polarized S K- and L-edge, Mo L₃- and L₂-edge x-ray absorption near-edge structure (XANES) of natural molybdenite (2H-MoS₂) have been measured with synchrotron radiation. These results are qualitatively interpreted using the energy band model of molybdenite and provide important information on the unoccupied states of molybdenite. The valence band (VB) maximum of molybdenite is characterized by fully occupied Mo 4d_z², and the conduction band (CB) minimum of molybdenite is characterized by unoccupied Mo 4d states. The unoccupied Mo 4d band is split into two sub-bands, designated as t_2g^–/t_2g⁺and e_g^–/e_g⁺sets. Although the relative energy of these two sets are difficult to be evaluated, probably the former has the lower energy than the latter, both two sets have the combination wave functions of the other unoccupied Mo 4d components, rather than the simple 4d_x² — y₂ and 4d_xy states. The unoccupied Mo 4d sub-bands contain significant DOS of both S 3 p- and 3 s-like states, indicating strong hybridization with S 3s and 3 p states. In the lower energy sub-band, the DOS of the S p_z- and p_x,y-like states are very similar. However, in the higher energy sub-band, the DOS of the S 3 p_x,y-like state is lower than that of the S 3p_z state. Polarized S K-edge XANES also reveal the features of antibonding S p_z- and p_x,y-like states in molybdenite. The feature assigned to the S 3 p_z-like states is stronger and sharper, and shifts to lower energy by about 2 eV relative to that for the S 3 p_x,y-like states.