Si(100) suface undergoes surface reconstruction phase transition from the low temperature c(4×2) structure to the high temperature 2x at about 200K. It has an anisotropic short range order above the transition temperature.

Step induced short range order on Si(100) reconstructed surfaces^{1)}

There are two kinds of interaction model proposed to the asymmetric dimer model of Si(100) reconstructed surface. One is the short ranged interaction model and the other is the one including the longer ranged electric dipolar interaction. Short range order structures at step edges are examined for the two kinds of the interaction model. Some differences are found between the two kinds of model. Comparison of the results to the STM images are attempted.

Theoretical Analyses of Thermal Desorption Spectra of Alkali Adsorbed Si(100) Surface ^{2)}

The thermal desorption spectra(TDS) observed of K on Si(100)2×1 reconstructed surface show two peaks and those peak temperatures shift with initial K coverage. In addition, the recent first principles calculation gives adsorption energy of this system for several coverages. TDS are calculated by making use of Monte Carlo simulation on the lattice gas model with parameters obtained from the results of the first principles calculation. The spectra agree qualitatively with the experimental ones and, however, they show quantitative disagreement on some important points. The next nearest neighbor interaction improves the calculated spectra and longer-ranged interactions seem to be needed to explain the spectra.