We have investigated the structure of Bi-adsorbed Si(I 0 0) 2 x n surfaces with various Bi coverages by low-energy. electron diffraction (LEED) and impact-collision ion scattering spectroscopy (ICISS). Intensities of He+ scattered from Bi and Si atoms were measured as a function of ion incidence angle. Bi-Bi interatomic distances for the toplayer including Bi-dimers were estimated by the shadow-cone technique. Bi-signal peaks appeared even at considerably large angles of incidence, which are attributed to collisions with Bi atoms in sub-surface layers. Bi adsorption is not completed at a mono-layer level, but continues to form multiple layers, fitted in the Si lattice, in the Frank-van der Merwe growth mode. (C) 2003 Published by Elsevier Science B.V.