Non-compact oxide-island growth induced by surface phase transition of the intermetallic NiAl during vacuum annealing.

Crystal structure and composition are inter-dependent and decoupling their effects on surface reactivity is challenging. Using low-energy electron microscopy to spatially and temporally resolve the oxide film growth during the oxidation of NiAl(100), we differentiate such coupled effects by monitoring oxide growth while simultaneously fine-tuning the surface structure and composition during oxidation. We demonstrate that the oxidation of chemically ordered surfaces results in compact oxide island growth whereas non-compact oxide growth during the surface phase transition. By incorporating the surface phase transition induced chemical disordering into kinetic Monte Carlo simulations, we show that the non-compact oxide growth is induced by the composition effect on the surface diffusion of oxygen, which can be described by the concept of "ant in the labyrinth". Image, graphical abstract [ABSTRACT FROM AUTHOR]