Kinetics study of antimony adsorption on Si(111)

In this paper, we use mass spectrometry (MS) and reflection high-energy electron (RHEED) to study the kinetics of adsorption of Sb on Si(1 1 1) surface and its relation to the corresponding surface structure. At high temperature (T > 800 degreesC) all the impinging Sb-4 molecules completely dissociate at the silicon surface and a 2D gas of Sb monomers reversibly adsorbs on the (1 x 1) surface. At low temperature (T < 600 degreesC) some impinging Sb-4 molecules act as precursors and can be partially reflected or desorbed while a 2D stable layer of Sb monomers irreversibly adsorbs. The surface continuously shifts from a blurred (7 x 7) surface to a (1 x 1) structure near completion of the 2D layer. In the intermediate range (600degreesC < T < 800 degreesC) provided that the coverage is large enough (theta similar to 2/3) the condensation of the 2D gas leads to a 2D (5root3 x 5root3) reconstruction. We show that introducing the formation of a condensed phase in a kinetics model allows us to reproduce our experimental data. Finally, we determine the adsorption geometry from ab initio calculations: Sb is adsorbed on top positions, somewhat passivating the Si surface dangling bonds. (C) 2003 Elsevier Science B.V. All rights reserved.