Coadsorbed oligolayers of beryllium and oxygen on molybdenum (1 1 2) surface: Formation and chemical composition, atomic structure and evaporation

Abstract

• Kinetics of oxygen adsorption and Be oxidation on the Be/Mo(1 1 2) surface was studied. • 2D honeycomb structures of BeO monolayer and nanoribbons on Mo(1 1 2) have been obtained. • Adsorbed BeO monolayers on Be/Mo(1 1 2) and Mo(1 1 2) decrease the work function. We have used Auger electron spectroscopy, low-energy electron diffraction, contact potential difference measurements and the density functional theory calculations to study oxygen adsorption on the supermonolayer Be/Mo(1 1 2) films as well as their composition and structure transformations under annealing. Adsorption of oxygen on Be–Mo(1 1 2) results in the synthesis of BeO at room temperature, and the film becomes a two-component system consisting of oxidized and non-oxidized Be. Under annealing in the temperature range 1100–1250 K, the non-oxidized Be desorbs and only BeO remains on the surface up to 1500−1600 K. Desorption of non-oxidized Be results in BeO ordering to a commensurate structure (1 × 1) identified as a 2D honeycomb nanosheet. Formation of overlayers depleted of Be and O is observed during desorption of BeO. A model of honeycomb nanoribbons is suggested for their structure. Adsorbed BeO monolayers were found to reduce the work function of the Mo(1 1 2) and Be/Mo(1 1 2) surfaces.