INTERACTION OF NO2 WITH RU(001) - FORMATION AND DECOMPOSITION OF RUOXLAYERS

We have investigated, using temperature-programed desorption, high-res olution electron energy loss spectroscopy and low-energy electron diff raction, the formation and decomposition of the suboxides of Ru which form after exposure of NO2 to the Ru(001) surface. The NO2 (radical) m olecule is not limited by any significant kinetic barrier to its decom position even at the high oxygen coverages considered. It is this barr ier which restricts measurable rates of dissociative chemisorption of O-2 to surface coverages below 0.5 under ultrahigh vacuum conditions. We have identified a subsurface state which is occupied after saturati on of the surface overlayer. Utilizing isotopically labeled molecular oxygen and a detailed mixing/segregation model, we have been able to e lucidate and quantify the nature of mixing between the surface and sub surface oxygen as a function of total oxygen uptake. (C) 1996 American Institute of Physics.