Structural and electronic properties of barium-induced surfaces on Si(111): Barium disilicide and Si(111)2 × 8 reconstruction

Abstract

The structural and electronic properties of a BaSi2(100) film as well as Ba-induced surface reconstructions formed on Si(111) have been investigated by scanning tunneling microscopy and spectroscopy (STS). At a low Ba deposition rate (∼0.1 nm/min), no silicide structures grow but only Si surface reconstructions are formed. In contrast, when Ba atoms are evaporated onto the Si(111) surface at 600 °C at a deposition rate of ∼1 nm/min, most of the surface was covered with a striped structure, which is assigned to the BaSi2(100) surface terminated with Si4 tetrahedra, which is consistent with a previously reported structural model [Okasaka et al., Surf. Sci. 635, 115 (2015)]. On an identical sample, another surface phase having -R30° periodicity was observed. This would also be the surface terminated with Si4 tetrahedra but with two-thirds of Si4 tetrahedra missing owing to the shortage of Si supply from the substrate. STS spectra obtained for both the striped and -R30° periodic structures exhibit a bandgap of 1.3 eV.