AVS 53rd International Symposium
    Surface Science Wednesday Sessions
       Session SS1-WeA

Paper SS1-WeA2
Diffusion and Clustering of Ag Atoms on a Si(111)7x7 Surface

Wednesday, November 15, 2006, 2:20 pm, Room 2002

Session: Growth Processes on Metal and Semiconductor Surfaces
Presenter: S. Suto, Tohoku University, Japan
Authors: S. Suto, Tohoku University, Japan
J. Osiecki, Tohoku University, Japan
K. Takusari, Tohoku University, Japan
H. Kato, Tohoku University, Japan
A. Kasuya, Tohoku University, Japan
Correspondent: Click to Email
We report here the measurements of the diffusion and clustering of silver atoms on a Si(111)7x7 surface at room temperature using scanning tunneling microscopy (STM). The 7x7 structure is made of relatively large unit cells, which consist of faulted and unfaulted triangular half unit cells (HUCs). There are intercell hopping and intracell motion of Ag atoms. Up to now, the atomistic intercell diffusion of single Ag atoms and formation process of dimers was already reported by Sobotik et al.@footnote 1@ We evaporated the Ag between 0.001ML and 0.088ML on the Si(111)7x7 surface and then observed the relaxation of deposited Ag atoms for 150 min. The intercell hopping and clustering inside the HUCs were observed. First, we discuss the hopping rates and atomistic formation process of dimer, trimer, tetramer and pentamer with the theoretical model proposed by Vasco et al.@footnote 2@ The intercell hopping rates are 1.6 x 10@super -4@ 1/s from unfaulted to faulted HUCs and 1.3 x 10@super -5@ 1/s vice versa. The cluster formation process indicates the cooperative diffusion growth; the hopping rates depend on the occupation numbers of target HUCs. Second, we present the intracell motion of dimers and trimers. Third, we discuss the initial stage of nucleation. The conformation of tetramer adjacent to monomer is very stable. The monomer doesn't jump to teteramer. The tetramer doesn't show the intracell motion and the motion may contribute clustering and stability. We discuss the significance of the intercell and intracell diffusion upon clustering and nucleation. @FootnoteText@ @footnote 1@P. Sobotik et al., Surf. Sci. Lett. 537, L442(2003).@footnote 2@E. Vasco et al., Phys. Rev. B 67, 2355412(2003).