Structural studies of the Mg/Si(111) interface formation

• Published in: Surface science 1990-01, Vol.225 (3), p.233-241
• Main Authors: Vandré, D., Incoccia, L., Kaindl, G.
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solid-gas interface; Surface physical chemistry
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(90)90443-C

Structural aspects of the formation of the Mg/Si(111) interface at room temperature were investigated by surface EXAFS at the Mg K threshold. Bond lengths and the symmetry of the adsorption sites were determined as a function of Mg coverage. The Mg atoms are found to adsorb on fourfold sites above second-layer Si atoms (T 4)it, with bond distances to first- and second-layer Si atoms equal to 2.60 ± 0.04 Å and 2.47 ± 0.04 Å, respectively. While in the initial stage of adsorption, no adsorbate-induced LEED pattern is observed, the Mg atoms on T 4it positions give rise to a (√3 × √3)R30° superstructure at a coverage of 1 3 ML. Further Mg deposition preserves the LEED pattern, while the polarization-dependent SEXAFS spectra reflect the presence of additional Mg atoms at off-centered T sites midway between two Mg atoms at T 4it sites. At coverages above 1 ML Mg, the LEED pattern disappears, and a contraction of the Mg-Mg bond distance to the bulk value is found.