Direct STM observation of surface modification and growth of AgCl islands on Ag(111) upon chlorination at room temperature

The results of STM, AES and TDS study of a Ag(lll) surface treated by molec ular chlorine in UHV with doses up to 100000 L are presented. We obtained d irect evidence of AgCl island formation on the surface upon chlorine adsorp tion at room temperature. The specific feature of the modified silver surfa ce is AgCl islands surrounded by ditches with 50-150 Angstrom depth and unt reated atomic plateaux. The atomic structure and chemical state of the surf ace area with no AgCl islands corresponds to saturated chlorine monolayer w ith a Ag(111)-(17 x 17)-Cl structure. A strong influence of AES primary ele ctron beam on the morphology of the silver chloride film was observed by ST M. A small (0.1 C cm(-2)) electron beam dose caused a tremendous modificati on of the AgCl island film forming 'giant' AgCl islands surrounded by a smo oth surface covered by chemisorbed chlorine. This surface modification coul d be an origin of discrepancy in the interpretation of previous electron sp ectroscopy results. (C) 1999 Elsevier Science B.V. All rights reserved.