Electronic structure of molybdenum disulphide

Abstract

X-ray emission spectra (S, Kβ_1,3 and L_2,3M; Mo, Lβ_2,15 and 5p→ 3d) and valence band X-ray photoelectron (X.p.) spectra from molybdenum disulphide were aligned on a common energy scale using X.p. core data. These spectra show that Mo 4d character is extensively present in the so-called “sulphur p band” and that sulphur 3p character is also present in the least tightly bound “Mo 4d_z²” orbital. Mo 5p and S 3s orbitals are also shown to play a part in covalent bond formation in the “p band”. The general picture that emerges is one of extensive covalent bonding between molybdenum and sulphur. The structure of the spectra can be adequately rationalised using a simple molecular orbital model based upon a MoS₆(D_3h) unit.