The initial stages of Yb/Si(l 0 0) interface growth have been studied by scanning tunneling microscopy, low-energy electron diffraction, Auger electron spectroscopy (AES), thermal desorption spectroscopy, and work-function change measurements. It is shown that a two-dimensional (2D) adsorbed layer of Yb forms at low coverage (<0.5-0.6 monolayers (ML)), followed by three-dimensional (3D) growth of Yb silicide phase at higher coverages. The two surface reconstructions of Yb/Si(l 0 0), 2 x 3 and 2 x 6 phases, are identified in submonolayer regime. The submonolayer adsorbed phases are found to exhibit higher thermal stability compared to the silicide one. The formation of adsorbed phases results in a large decrease of work-function (by up to 1.8 eV), which suggests that the reconstructions are terminated by Yb and a charge transfer occurs from top Yb atoms to underlying Si substrate. Moreover, the structural model of the 2 x 3 reconstruction is proposed and the features of the 2 x 6 phase are interpreted. (C) 2003 Elsevier Science B.V. All rights reserved.