Sodium adsorption on the surface of thermally oxidized tungsten

Photoelectron spectroscopy was used to study the electronic structure in situ in an ultrahigh vacuum before and after the adsorption of sodium atoms on the surface of tungsten oxidized at an oxygen pressure of 1 Torr and a temperature of 950 K. The photoemission spectra from the valence band and the W 4$f$, O 2$s$, and Na 2$p$ core states were studied under synchrotron excitation in the photon energy range 80–600 eV. It is found that a tungsten oxide film is formed containing various tungsten oxides with an oxidation state of 6+ to 4+. The deposition of a 1.1 monolayer of sodium atoms on the surface of oxidized tungsten leads to the reduction of the W$^{6+}$ states to W$^{4+}$ and the reaction with oxygen in the hydroxyl composition, which is reflected in the change in the spectrum of the W 4$f$ and O 2$s$ core states. It is shown that the cathodoluminescence spectrum is associated with the luminescence of tungsten oxide.