High-resolution Si 2p core-level and low-energy electron diffraction studies of the Ca/Si(1 1 1)-(3 × 2) surface

We have investigated the surface structure of the Ca/Si(1 1 1)-(3 × 2) surface using low-energy electron diffraction (LEED) and high-resolution core-level photoelectron spectroscopy. Weak ×2 streaks were observed in LEED at 300 K. After cooling the sample to 100 K, ×2 spots, which originate from both (3 × 2) and c(6 × 2) periodicities, appeared. By considering the energy shift and intensity of each surface component observed in the Si 2p core-level spectra, we conclude that the structure of the (3 × 2) surface is basically the same as that of the honeycomb-chain-channel model with a Ca coverage of 1/6 ML. Further, we propose that the weak ×2 streaks at 300 K result from thermally induced disorder.