AVS 47th International Symposium
    Surface Science Monday Sessions
       Session SS3-MoA

Paper SS3-MoA8
LEEM Study of Mass Transport on Si(111)

Monday, October 2, 2000, 4:20 pm, Room 210

Session: Surface Diffusion and Wetting
Presenter: H. Hibino, Arizona State University
Authors: H. Hibino, Arizona State University
C.-W. Hu, Arizona State University
T. Ogino, NTT Basic Research Laboratories, Japan
I.S.T. Tsong, Arizona State University
Correspondent: Click to Email
How does the surface morphology change during annealing, growth, and/or sublimation? In order to ask the question, we need understanding of the process of the mass transport. In this paper, we investigate two aspects of mass transport on Si(111) using LEEM. One aspect is the decay of 2-dimensional islands or holes near the phase transition between 1x1 and 7x7. The evolution of the island or hole provides the information about the rate-limiting process. The radii of the islands and holes show power-law dependences on time. The measured exponents are close to 1/3 rather than 1/2. This means that the decay is governed by the diffusion of atoms on the terraces rather than the attachment and detachment of atoms at the steps. We also measure the decay rate as a function of the temperature, and clarify that the decay rate changes steeply at the phase transition between 1x1 and 7x7. The decay rate is faster on 1x1 than on 7x7. The other aspect is the shape changes of the islands and holes during the 1x1-to-7x7 phase transition. The atom density in 1x1 is higher than that in 7x7. This difference in the atom density causes the steps to advance during the 1x1-to-7x7 phase transition. Comparing the changes of the islands and holes, the island tends to capture more atoms than the hole. More atoms are incorporated into the step from the lower terrace than the upper terrace. The 7x7 reconstruction nucleates at the upper step edges. Therefore, this result as well as the faster decay rates of islands and holes on 1x1 than on 7x7 suggest that the mass transport is faster on 1x1 than on 7x7.