Temperature-induced phase transitions of the Si(1 0 0) and (1 1 3) surfaces

We report in this paper the effect of adatoms and structural vibrations on temperature-induced phase transitions of surfaces at elevated temperatures. In the case of Si(1 0 0) surface, a temperature-induced metallization takes place at about 600 K without any change in low energy electron diffraction pattern. Photoemission spectroscopy reveals that the metallization is not related to the (instantaneous) symmetrization of asymmetric dimers. Si adatoms produced at elevated temperatures are suggested to play a role of donor, giving rise to the metallization. On the other hand, the Si(1 1 3) surface exhibits a structural phase transition between 3×2 and 3×1 phases at about 800 K. The local structure of the 3×2 surface at room temperature seems to be the same as that of the 3×1 surface at 800 K. We propose that the temperature-induced phase transition on Si(1 1 3) is an order–disorder transition due to the thermal fluctuation of two types of tetramer, which can be easily understood within the two-dimensional Ising model.