The Au adsorbed Si(111)5×2 surface structure with short range order is known by measurements of LEED and RHEED. It was believed that the Au adsorbates form the linear chain with lattice constant 2a (a is lattice constant of Si triangular lattice) and short range order between the chains would result streaks. However, the STM measurements reveal that the structure of this surface system is more complex than what was thought in the LEED and RHEED experiments.

Correlation function of adsorbed Au chain on Si(111) surface Y. Yagi, K. Kakitani and A. Yoshimori Surface Science, in press.

The Au adsorbed Si(111)5×2 surface structure with short range order has been seen through the STM measurements. Particularly, the one dimensional chains supposed to consist of adsorbed Au atoms are clearly observed. A one dimensional lattice gas model is constructed for this chain with repulsive interaction and some irregularity assumed corresponding to the STM observation. The theoretical positional correlation function of the adsorbed Au is obtained by Monte Carlo simulation with fitting parameters of the repulsive interaction and of the irregularity to the experimental ones. Almost complete fitting is obtained, from which reasonable values of the repulsive interaction and concentration of the irregularity are obtained. A rigorous analysis is made also on another one dimensional model to describe the interchain correlation on this surface to compare with the experiments.