Chlorine monolayers on the low-index faces of silver

Abstract

Chlorine chemisorption layers were obtained on the (100), (110) and (111) faces of silver single crystals by means of the reaction with dichloroethane. The structure and stability of the surface phases was studied mainly by LEED and Auger spectroscopy. On the (100) face, a c(2 × 2) superstructure was found at all coverages, which was interpreted as a reconstructed layer with a structure similar to that of the AgCl (100) planes. On the other two faces, different superstructures were observed, depending on the coverage. At low coverages, (2 × 1) and (√3 × √3)-R 30° superstructures were found on the (110) and (111) faces, respectively, which seem to be better interprétable as reconstructed layers. At maximum coverages, c(4 × 2) and (3 × 3) superstructures were observed respectively on the two faces. These phases were interpreted as mixed layers with a packing of the silver and chlorine atoms similar to that of the AgCl (111) planes. The proposed models are in agreement with the different thermal stabilities of the layers. The models of the maximum-coverage structures correspond to about the same chlorine amount on the three faces, in agreement with the Auger results. The structures are also discussed in relation to the known epitactic relations for the growth of AgCl on silver.