Surface electronic structures of the Eu- and Ca-induced so-called Si(111)-(5x1) reconstructions

We have investigated the electronic structures of the so-called Eu- and Ca-induced Si(111)-(5x1) surfaces by using angle-resolved photoelectron spectroscopy (ARPES) and low-energy electron diffraction (LEED). The LEED patterns of these surfaces indicate that the periodicities of both surfaces are actually (5x4). In the ARPES study, seven surface states were observed on each (5x4) reconstruction. Of these surface states, the dispersions of five of them show good agreement with those of the Eu- and Ca-induced (3x2) honeycomb-chain-channel (HCC) surfaces and the dispersions of the two other states agree well with those of the Eu- and Ca-induced (2x1) Seiwatz surfaces along the [(1) over tilde 10] direction-i.e., the direction parallel to the adsorbate chain. Taking the dispersion behavior of these surface states into account, we conclude that the interaction between the nearest-neighbor HCC chain and Seiwatz chain is quite small and that the electronic structure of one chain hardly affects the electronic structure of its neighboring chain. We also discuss the atomic structure of the Eu- and Ca-induced Si(111)-(5x1) reconstructions based on their electronic structures.