LEED AND AES STUDY OF THE ADSORPTION OF CHLORINE ON W(100) AT ROOM-TEMPERATURE

The surface structures formed on room temperature adsorption of chlorine on W(100) and subsequent annealing of the saturated surface have been characterised by LEED. The progress of gas adsorption was followed by AES which was also used to observe relative chlorine coverage on annealing. Room temperature adsorption was random up to the saturation exposure of 1.7 L. On annealing the chlorine adlayer ordering commenced at about 800 K. One-dimensional ordering into rows along the <1, 1> directions was followed by the ordering of these into two 2D structures: an interpenetrating 7 1 1 1 at 830 K and an interpenetrating 5 1 6 1 for 860 K and above. Desorption started after 1050 K annealing and was complete by 1440 K. Saturation chlorine coverage is inferred as 5 × 1014 atoms cm-2 and the single desorption peak coupled with the LEED analysis suggests that chlorine is bridge bonded to the W(100) surface for the ordered overlayer. © 1979.