Scanning tunnelling microscopy and core-level photo-emission spectroscopy experiments demonstrated that an ordered surface reconstruction of Pb, Sn and Si adatoms (1/3ML overall coverage) could be formed with (√3 x √3)R30° symmetry on the Si(111) substrate. The Pb, Sn and Si atomically intermixed; occupying T4 sites as in the case of the well known pure 1/3ML Sn or Pb (√3 x √3)R30° reconstructions. The electronic structure of this surface, investigated with scanning tunnelling spectroscopy and valence band photo-emission, exhibited semiconducting behaviour (0.4eV band-gap), and two surface bands centred at ±0.7eV with respect to the Fermi level. These features were significantly different from those of the electronic structure of the binary Pb–Si/Si(111) and Sn–Si/Si(111) 2D alloys. This occurrence demonstrated that tailoring the electronic structure of a surface alloy was viable just by mixing adatoms with the same valence and different sizes.

Electronic Structure of a Two-Dimensional Alloy - Sn–Pb–Si on Si(111). C.Di Teodoro, B.Ressel, K.C.Prince, V.Cháb, S.Santucci, S.Faccani, G.Profeta, L.Ottaviano: Journal of Physics - Condensed Matter, 2004, 16[21], 3507-16