The effect of electron beam irradiation on the chemistry of molybdenum hexacarbonyl on thin alumina films in ultrahigh vacuum

The interaction of incident electron beams with molybdenum hexacarbonyl (Mo(CO)6) adsorbed on thin, dehydroxylated alumina films grown on a molybdenum substrate is studied in ultrahigh vacuum using primarily temperature-programmed desorption (TPD) and reflection– absorption infrared spectroscopies (RAIRS). It is found that electron beams induce decarbonylation, forming both subcarbonyls and a stable surface oxalate species, where it is found that a Mo(CO)2 species is the precursor to the formation of oxalate species. A similar oxalate species is formed on dehydroxylated alumina by heating a Mo(CO)6-covered surface to above ∼205 K, but the amount formed by electron beam irradiation is ∼3.5 times larger. It is shown that electron beam energies of ∼10 eV or greater are required to cause extensive decarbonylation and that the majority of the surface decomposition is caused by an electron dose of ∼6 mC/cm2. © 2003 Elsevier B.V. All rights reserved.