AVS 46th International Symposium
    Surface Science Division Thursday Sessions
       Session SS2+EM+NS-ThM

Paper SS2+EM+NS-ThM11
The Growth of High Density, Small Ag Islands at the Si(111)7x7 Surfaces with Adatom Defects

Thursday, October 28, 1999, 11:40 am, Room 607

Session: Nucleation and Growth
Presenter: H. Hirayama, Tokyo Institute of Technology, Japan
Authors: H. Hirayama, Tokyo Institute of Technology, Japan
H. Okamoto, Tokyo Institute of Technology, Japan
K. Takayanagi, Tokyo Institute of Technology, Japan
Correspondent: Click to Email
We studied the growth of Ag islands on the Si(111)7x7 surfaces with missing adatoms. The missing adatoms were created by 0.5keV Ar ion bombardment. Ag atoms were deposited on the surfaces at room temperature. The growths were observed by using scanning tunneling microscope (STM). At the Si(111)7x7 surface of no missing adatoms, several half unit triangular cells of the 7x7 reconstruction changed their contrast to be bright in the initial stage of the Ag deposition . Then, at the coverage above 0.03 monolayer (ML), each bright triangular cell changed to a bright spot. With the coverage, the number of bright spots increased, and occasionally two spots in neighboring cells kissed. At 0.8ML, the surface was covered by the two-dimensional (2D) percolating network of kissing spots. On the network, three-dimensional (3D) Ag islands grew. Meanwhile, at the Si(111)7x7 surfaces with missing adatoms, the bight spots appeared at the very early stage of the Ag deposition. The spots appeared as to avoid missing adatom sites. This resulted in an imperfect 2D network; the connection of kissing spots were cut into pieces here and there. On the imperfect 2D network, 3D islands grew above 0.7ML. At the stage of the 3D island growth, the missing adatom sites of the underlying 2D network was never filled up. However, we found strong dependence of the size and density of the 3D islands on the number of missing adatoms at the starting surfaces. With an increase of missing adatoms, the size of the islands decreased, while the density increased dramatically. The effects of the missing adatoms on the 3D Ag islands growth were attributed to the substantial increase of the super saturation and the decrease of the diffusion constant of Ag atoms on the imperfect 2D network.