LEED and ARPES study of oxygen induced surface reconstruction and electronic structure of Mo(110)

The adsorption of oxygen on Mo(110) surface is studied by a combination of Low Energy Electron Diffraction (LEED) and Angle-Resolved Photoemission Spectroscopy (ARPES) measurements with fine coverage dependence. Oxygen adsorption at Mo(110) surface corresponds to ordering in a single-phase region p(2×2) and in a two-phase coexistence region p(2×1) structure at low and medium coverage respectively. Energy degeneracy of adsorption sites plays a significant role in the occurrence of two-domain structure. For moderately higher coverage, we observe the occurrence of a single-phase p(2×6) structure. Higher temperature oxygen annealing forms Molybdenum oxide (MoO2 ) on top of Mo(110) substrate surface. Band structure of clean Mo(110) surface exhibits the presence of d-derived surface states in the mid-region of the Γ¯ to N¯ symmetry line. We also observe dispersive bands, including both positive and negative curvature due to adsorption of oxygen on Mo(110) surface. Curvature of the Oxygen induced surface band gets reversed along Γ¯ to N¯ symmetry direction. Dispersive nature of oxygen-induced band increases at Γ¯ point with increasing oxygen coverage on the Mo(110) surface.