Bromine adsorbed silver (111) surfaces with (root 3 x root 3)R30 degrees an
d (3 x 3) phases were studied by scanning tunneling microscopy at room temp
erature. For the (root 3 x root 3)R30 degrees surface, no feature associate
d with the Br overlayer could be obtained: only the substrate (1 x 1) struc
ture was observed. On the other hand, for the (3 x 3) phase, it was reveale
d that a bromine overlayer is formed with hexagonal arrangement, of which t
he lattice constant is 3/2 that of the substrate. It was also found that th
e coadsorbed cadmium atoms change the Br overlayer structure. (C) 1999 Else
vier Science B.V. All rights reserved.