Harumo Morikawa

Si(111)-√21×√21-(Ag+Cs) Surface Studied by Scanning Tunneling Microscopy and Angle-Resolved Photoemission Spectroscopy

Scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) were used to study the atomic and electronic structures of the Si(111)-√21×√21-(Ag+Cs) surface (√21-Cs in short), which was induced by depositing caesium atoms on the Si(111)-√3×√3-Ag surface at room temperature (RT). Compared with previously reported STM images of noble-metal induced √21×√21 phases including the Si(111)-√21×√21-(Ag+Ag) and Si(111)-√21×√21-(Ag+Au) surfaces (√21-Ag and √21-Au, respectively), the √21-Cs surface displayed quite different features in STM images. The ARPES data of the √21-Cs surface revealed an intrinsic dispersive surface-state band, together with a non-dispersive one near the Fermi level, which was also different from those of the √21-Ag and √21-Au surfaces. These results strongly suggest different atomic arrangements between Cs- and noble-metal induced √21×√21 phases. Unlike the √21-Ag and √21-Au phases, the framework of the initial Si(111)-√3×√3-Ag substrate is totally broken at the √21-Cs phase.