Electronic structure of an ultrathin molybdenum oxide film

The electronic structure of an ultra-thin molybdenum oxide film obtained by oxidation of molybdenum at an oxygen pressure of 1 Torr and the effect of adsorption of sodium atoms Na on its electronic structure are studied by ultra-vacuum photoelectron spectroscopy in ultrahigh vacuum. Photoemission spectra from the valence band and core levels of O $2s$, Mo $3d$ Mo $3p$, and Na $1p$ are studied, upon synchrotron excitation in the photon energy range 80 – 600 eV. It is shown that in the formed oxide film, molybdenum is in two states: Mo$^{6+}$ and Mo$^{4+}$. On the surface of the oxide, oxygen is induced both in the composition of the oxides and in hydroxyl. It was shown that MoO$_3$ is formed on the surface, and MoO$_2$ at a distance from the surface. The deposition of Na atoms leads to intercalation of the molybdenum oxide layer.