X-ray Photoemission Spectroscopy Studies of the Semiconducting Molybdenum Purple Bronze Bi0.2MoO3

The electronic structure of the quasi-two-dimensional (2D) semiconducting molybdenum purple bronze Bi0.2MoO3 was presented by X-ray photoemission spectroscopy. The valence band of Bi0.2MoO3 is made up of Opπ nonbonding level, π and σ bonding bands. The peak at 1.5 eV and the shoulder at 0.5 eV in the forbidden band may be formed from the non-bonding dxy orbitals of some Mo atoms. The O1s core-level spectrum demonstrates the presence of two inequivalent bonds of oxygen ions in Bi0.2MoO3. Bi4f core-level spectrum shows two bonding characters of Bi atoms in bismuth molybdenum single crystal. Mo3d core-level spectrum confirms two kinds of valence states of Molybdenum (Mo 5 and Mo 6). Ar ion irradiation induces more significant distortion of MoO6 octahedra.