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

Paper SS3-MoA10
Surface Supercooling and Stability of Si(111)-"1x1" High Temperature Phase

Monday, October 2, 2000, 5:00 pm, Room 210

Session: Surface Diffusion and Wetting
Presenter: C.-W. Hu, Arizona State University
Authors: C.-W. Hu, Arizona State University
H. Hibino, NTT Basic Research Laboratories, Japan
T. Ogino, NTT Basic Research Laboratories, Japan
I.S.T. Tsong, Arizona State University
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Si(111) high temperature phase transition is one of the most studied surface processes. It is well known that high temperature "1x1" phase converts into the most stable (7x7) surface reconstruction at about 830°C by the first order phase transition. However, the high temperature "1x1" phase can be locked down to 10~20°C below the phase transition temperature. This supercooling behavior is in situ observed by low energy electron microscopy within µm-sized two-dimensional depressions on Si(111) surface. The phenomenon can be readily explained as the lack of the nucleus of (7x7) reconstruction in depressions because the step edges of upper terrace take the roles of nucleation centers for stable (7x7) reconstruction. The supercooling temperatures are observed strongly depending on the sizes of depressions and the cooling rates of Si substrate. A normal depression with (7x7) reconstruction on it is formed by fast cooling through phase transition temperature. In this way, the filling-up rates can be measured respectively for supercooling depressions and normal depressions. The preliminary experimental results exhibit the downward movement of Si adatoms from (7x7) upper terrace and the step-edge attachment within depressions are responsible for the stability of Si(111)-"1x1" supercooling phase.