The structure of adsorbed monolayers. The surface chemical bond

Results from new electron and ion spectroscopies with surface sensitivities of less than 1% of a monolayer have greatly increased our knowledge of structure and bonding at the solid-vacuum interface. We present here a case-history of some of the major conclusions of these surface structural studies. Results on metal single crystal surfaces of surface composition using Auger electron spectroscopy, bond energetics using thermal desorption spectroscopy, and bonding geometries using low-energy electron diffraction and high-resolution electron energy loss spectroscopy are highlighted. A wide variety of bonding geometries and bond energies are found — one of the major reasons for the diverse reactivity and chemistry of surfaces. Recent work combining vacuum, surface science techniques with studies at solid-gas and solid-liquid interfaces shows promise in extending our understanding of surface structure and bonding to these interfaces.