Mode transition between growth and decomposition of oxides on Si(001): Kinetically determined critical coverage for oxidation

Effects of preoxidation on the reaction kinetics of oxygen molecules at Si( 001) surface have been investigated by real-time ultraviolet photoelectron spectroscopy. A mode transition from decomposition to growth of surface oxi des was found to exist at a certain initial oxide coverage, which is kineti cally, not energetically, determined. By considering a change of balance be tween Si adatom and oxygen-monomer fluxes at the perimeter of oxide cluster s, this mode transition is quantitatively described as a bifurcation of an autocatalytic-reaction rate equation. (C) 2000 American Institute of Physic s. [S0003-6951(00)03346-5].