The structure of atomic oxygen and carbon overlayers on the Mo(001) surface studied by low energy ion scattering

Abstract

The bonding geometry of atomic overlayers composed of submonolayer quantities of pure oxygen, pure carbon, and a mixture of carbon and oxygen on a Mo(100) surface has been studied for the first time by low energy angle-resolved K+ and Li+ ion backscattering. The surface composition and long range ordering of the clean and adsorbate-covered surfaces were also characterized by Auger and LEED. The overlayers were generated in UHV by dissociative adsorption of O2 or CO or by thermal cracking of C2H4 on the clean Mo(100) surface. The absence of double scattering along the [110] direction for the oxygen overlayer compared to the clean surface indicates that the oxygen atoms are located in fourfold hollows on the surface. This is confirmed by Monte Carlo simulations of the K+ scattering. Li+ scattering results corroborate this structural model. The K+ scattering energy distributions from pure carbon and mixed carbon/oxygen overlayers are very similar to the oxygen overlayer suggesting that carbon is also situated in the fourfold hollow.