Surface roughness of the strained polycrystalline copper during the early stage oxidation.

Using the reactive molecular dynamic simulation, the surface roughness and oxide layer morphology are studied during the early oxidation of polycrystalline copper under applied tensile strains at 900 K. We find that the surface roughness of oxide layer increases with the formation and growth of oxide islands. The transformation of oxide wetting layer to the island structure occurs as a result of atom diffusion triggered by the oxidation-induced growth stress. Such a transformation process is enhanced by promoting the free energy of copper atoms, especially along the grain boundary when the external tensile strain is applied. This new insight provides a fundamental interpretation of the instability of oxide layer and the origin of surface defects under applied tensile loadings. [ABSTRACT FROM AUTHOR]