Electronically stimulated desorption of neutral atoms from Ar films on Ru(001): Desorption mechanisms and energy-transfer processes derived from distributions of kinetic energy

Desorption yields as well as kinetic-energy distributions of desorbing argon atoms were investigated for pure argon films of variable thickness (annealed and not annealed), and for Ar samples doped with ${\mathrm{N}}_2$, ${\mathrm{O}}_2$, and NO additives of (a) 1% and 5% concentration in the bulk, and (b) 1/4 to 1/2 monolayer on the surface. The preparation-dependent prevalence of different desorption processes is investigated. Bimodal energy distributions are obtained from clean, annealed samples which are drastically changed by dopants as well as lattice defects. From thick, annealed samples the yield ratio of fast to slow particles is found to be 1.6, which is much larger than reported for previous experiments. This indicates that perfect vacuum conditions are decisive for the study of such systems if mechanistic conclusions are to be drawn.