Transition from random to island growth mode during Si(100)-(2 x 1) dry oxidation and its description with autocatalytic reaction model

Time evolutions of O 2p intensity during the first monolayer growth of dry oxides on Si(100)-(2 X 1) surface as obtained by real-time ultraviolet-phot oelectron spectroscopy (UPS) shows two types of evolutions: Langmuir-Hishel wood type in the low-T/high-P region and a sigmoid-like type in the high-T/ low-P region. Preoxidation experiments demonstrates that the former corresp onds to the random-adsorption mode and the latter to the 2D-island growth m ode. The obtained time evolutions for the two modes, not only the initial s tage but also the one up to one monolayer coverage, are almost perfectly de scribed with the autocatalytic reaction model developed by the authors. The physical background of the model is discussed to show that the coalescence of islands is properly involved in the model, which accounts for its abili ty. (C) 2000 Elsevier Science B.V. All rights reserved.