Ab initio study of thallium nanoclusters on Si(111)-7x7

We have studied the stability of a thallium nanocluster of various numbers of atoms (N=1,2,...,10) on a Si(111)-7x7 substrate using density functional theory total energy calculations. We have compared it with clusters of other group III elements (Al, Ga, and In). Thallium is found to be unstable with the triangular cluster, which has been known to be stable for other group III elements. Instead, a slightly different structure, in which Si atop atoms are lower than thallium atoms in height by 2.56 angstrom, was found to be quite stable. Such an abnormal structure originates from the inert pair of 6s(2) electrons due to the significant spin-orbit interaction. The initial relaxed N=6 Tl cluster continues to grow with increasing N up to N=9 in the faulted-half unit cell, which is consistent with experimental observationsclose121

Scanning tunneling microscopy at multiple voltage biases of stable "ring-like" Ag clusters on Si(111)-(7×\times7)

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.Comment: 9 pages and 5 figure