SURFACE ELECTRONIC-STRUCTURE OF SI(001)2X2-IN STUDIED BY ANGLE-RESOLVED PHOTOELECTRON-SPECTROSCOPY

Angle-resolved photoelectron spectroscopy (ARPES) using synchrotron ra diation was employed to study the electronic structure of a well-order ed single-domain Si(001)2x2-In surface. The existence of five surface state bands, denoted as S-1, S-2, S-2('), S-3, and S-3(') is revealed within the bulk band gap between 0.6 and 2.2 eV in binding energy (E(B )). The dispersions of these surface states are determined for most of the symmetry axes in the 2X2 surface Brillouin zone (SBZ), which turn out to be essentially identical to those observed for Si(001) 2X2-Al recently [Surf. Sci. Lett. 321, L177 (1994)]. Symmetries of the surfac e states with respect to two mirror axes of the SBZ are determined by the polarization dependence of ARPES intensities. A comparison to a th eoretical calculation makes it possible to determine that the smallest E(B) State S-1 is due to the In dimer bond and S-2, S-2('), S-3, and S-3(') are due to bonds between In dimers and topmost Si atoms, and th at the In dimers are parallel to the substrate Si dimers. Besides thes e five surface state bands, two other spectral features are observed w ithin the bulk band gap, which can be related to similar features obse rved for a clean Si(001) surface.