Electronic and atomic structure of two-dimensional ErSi2 (1x1)-H on Si(111)

The electronic and atomic properties of H chemisorbed on the two-dimensional (2D) ErSi2 (1 x 1) surface are studied using the extended Huckel theory method. Calculated electronic density of states and 2D band structure of various H chemisorption geometries are compared with angle-resolved photoemission (ARP) data. From this comparison it is concluded that a geometry in which two H atoms are adsorbed per unit cell is the more consistent with the ARP data. They are bound respectively to the Si dangling bonds present at the ErSi2 surface and to Er in the interstitial voids of the Er hexagonal plane below Si species of the outermost atomic plane of the buckled Si top layer. We have also performed an overlap populations analysis, which allows us to trace back the unique buckling reversal of the Si top layer upon H saturation to an optimization of the Er-Si chemical bonding in H-saturated silicide.