Occupied surface-state bands of the (1 x 2) ordered phase of Bi/InAs(110)
The ordered (1 x 2) monolayer of Bi on the InAs(110) surface is studied by means of angle-resolved high-resolution ultra-violet photoemission at room temperature. Four bands of Bi;induced surface states are singled out and their dispersion is mapped along the high-symmetry directions of the surface Brillouin zone. The highest occupied state S' lies inside the InAs(110) energy gap at 0.2 eV binding energy and spreads across the Fermi level, determining the semimetallic character of the system. The second-highest occupied state Sn is located at 0.83 eV binding energy (at <(Gamma)over bar>), while states Sm and SN are located near the internal gap edge at 2.57 eV and 3.3 eV binding energy, and present band dispersions along <(Gamma)over bar>(X) over bar of similar to 340 meV and 300 meV, respectively. The Pi-induced bands of the (1 x 2) phase are shifted in energy relative to the corresponding bands of the (1 x 1)-Bi/InAs(110) phase and their width is reduced. These differences are discussed in the light of the geometric structure of the two phases.