  Since more than twenty years it is known that deposition of Ag onto
Si(111)-(7\times7) leads under certain conditions to the formation of so-called
"ring-like" clusters, that are particularly stable among small clusters. In
order to resolve their still unknown atomic structure, we performed voltage
dependent scanning tunneling microscopy (STM) measurements providing
interesting information about the electronic properties of clusters which are
linked with their atomic structure. Based on a structural model of Au cluster
on Si(111)-(7\times7) and our STM images, we propose an atomic arrangement for
the two most stable Ag "ring-like" clusters.
