Interaction of molybdenum hexacarbonyl with metallic aluminum at high temperatures: Carbide and alloy formation

The reaction of Mo(CO)6 on aluminum films grown on a Mo(1 0 0) substrate at 700 K is explored in ultrahigh vacuum using temperature-programmed desorption (TPD) and Auger and X-ray photoelectron (XPS) spectroscopies. Reaction with Mo(CO)6 at 700 K results in some oxidation of the outer layer of the aluminum film, and the formation of a molybdenum carbide, which incorporates some oxygen. The carbide stoichiometry varies initially from approximately MoC for carbonyl reacting with the aluminum surface, to Mo2C for thicker films. Heating this film to ∼1200 K results primarily in the desorption of carbon monoxide due to a reaction between the carbide and aluminum oxide. Metallic aluminum diffuses from the bulk of the film and some aluminum is found to desorb from the surface at ∼1270 K so that aluminum is retained on the surface due to the presence of the carbonyl-derived film. It is suggested that the aluminum can form an alloy with molybdenum at these higher temperatures.