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We have investigated the geometric structure of the so-called Ca/Si(111)-(5×1) surface using low-energy electron diffraction (LEED) and high-resolution core-level photoelectron spectroscopy. In LEED, dim extra spots besides the ×5 spots were observed after cooling the sample to 100 K. The positions of these dim spots reveal that this phase has a ×2 periodicity along its one-dimensional (1D) chains. In Si 2p core-level spectra, we observed five surface components. By considering the energy shift and intensity of each surface component and the 0.3 ML Ca coverage, we propose a structural model of this surface.

We have investigated the growth mechanism of SiC film by the thermal reaction of C60 molecules adsorbed on a Si(111)-(7×7) surface using photoelectron spectroscopy. The growth of SiC film, performed by repeating the sample annealing at 1370 K following the adsorption of C60 molecules, is confirmed by the profile of the valence spectrum. The bonding nature between C60 molecules and the SiC surface is considered to have a covalent character at 300 and 670 K, and both covalent and ionic characters at 870 K by the thermal-dependent valence and C 1s core level spectra of a 1 monolayer C60 film adsorbed on SiC. Furthermore, we determined that the breaking of the C60 cage and the formation of SiC occurred at 1070 K, i.e. at a temperature 100 K lower than that on a Si(111) surface.

We report here the temperature-dependent electronic structure of C60 molecules adsorbed on a Si(001)-(2×1) surface, measured by photoelectron spectroscopy. At room temperature, the valence spectra reveal that the interaction between a 1 monolayer (ML) C60 film and a Si(001)-(2×1) surface is mainly a physisorption. After annealing the 1 ML C60 film adsorbed on a Si(001)-(2×1) surface at 500 K, in the valence spectra the highest occupied molecular orbital (HOMO) of a C60 molecule splits into two peaks. The binding energies of the two peaks are 1.6 and 2.1 eV. We assign the 1.6-eV peak to the shifted HOMO and the 2.1-eV peak to the bonding state between C60 molecules and a Si(001)-(2×1) surface from the polarization-dependent measurement and the Si 2p core level spectrum. Moreover, the molecular orbitals and the C 1s core level of a C60 molecule shift to the lower binding energy side. These results indicate that the interaction between C60 molecules and the Si(001)-(2×1) surface changes from physisorption to chemisorption, which has both covalent and ionic characters, at 500 K.