Interaction of NF3 with Ru(0001): Order at steps

As part of a larger study of small fluorinated molecules on metal and semiconductor surfaces we investigated the adsorption of NF3 on Ru(0001) using measurements of electron-stimulated desorption ion angular distribution (ESDIAD), low-energy electron diffraction (LEED), thermal desorption spectroscopy, and Auger electron spectroscopy (AES). At 100 K, NF3 adsorbs with a high sticking probability. Some molecular NF3 desorbs on heating, with a peak maximum at 200 K. All molecular desorption is complete by 400 K, but AES shows that nitrogen and fluorine remain on the surface up to 1100 K. The LEED pattern of the majority of the surface remains (1 x 1) at all coverages and annealing conditions. At most locations on the Ru(0001) surface (planar regions), ESDIAD is dominated by F+ emission normal to the surface over the temperature range 100--1100 K. On stepped regions of the surface (near edges and defects) highly directional and intense hexagonal patterns of F+ emission are observed (200--1100 K). The off-normal beams desorb at 670 +- 30 away from the normal. It appears that most ESDIAD patterns in this system are derived from F or NF/sub x/ (x<3) fragments