Photoemission studies of α-Sn(1 0 0)2×1 surface

The electronic properties of a well ordered thick layer of α-Sn(1 0 0), grown on InSb(1 0 0), have been studied by core-level- and angle-resolved photoemission spectroscopy (ARPES). The surface was a double domain 2×1 showing a sharp LEED pattern with very low background at room temperature. ARPES spectra showed the presence of a surface state S1 dispersing along [0 1 0] direction towards higher binding energies with an overall dispersion of 1.2 eV. Such a behaviour has been observed for a similar surface state on Si(1 0 0)2×1 and Ge(1 0 0)2×1 (see [Semiconductor Surfaces and Interfaces, Springer, Berlin, 1995] and references therein) and undoubtedly attributed to Si or Ge asymmetric dimers. This result is in good agreement with the calculated S1 surface state band reported in [Phys. Rev. B 58 (1998) 13698]. The Sn 4d core levels lineshape was well fitted by four components, the bulk “B” and three chemically shifted doublets at binding energies +0.220, −0.230, and −0.490 eV with respect to “B”. Here again the energy positions and amplitudes are in good agreement with the predicted surface core-levels shifts of [Phys. Rev. B 58 (1998) 13698], taking into account final state effects, and attributed to down dimer-, second layer- and up-dimer-atoms, respectively.