Growth kinetics of a chemisorbed overlayer in the presence of impurities.

Abstract

The effects of random impurities on the growth kinetics of oxygen chemisorbed on the W(112) surface at halfmonolayer coverage are studied by high-resolution low-energy electron diffraction. An apparent deviation of the Lifshitz-Allen-Cahn growth law of the (2\ifmmode\times\else\texttimes\fi{}1) domains has been observed in the presence of nitrogen impurities in the early stage after the mixed overlayer is quenched from a random-lattice-gas state. An effective power law for the domain growth with R${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{2}$\ensuremath{\sim}${\mathrm{t}}^{\mathrm{x}}$, where R\ifmmode\bar\else\textasciimacron\fi{} is the average size of the domain, can be established. The effective exponent x was found to decrease from 1 as the density of the impurity increased. This result is consistent with recent theoretical calculations based on a random-field Ising model.