Dissociation preference of oxygen molecules on an inhomogeneously strained Cu(0 0 1) surface

Adsorption of oxygen molecules on an inhomogeneously strained Cu(0 0 1) surface is studied at room temperature by scanning tunneling microscopy using a grid pattern of the partly nitrogen-covered surface. On this surface, nitrogen-adsorbed patches with average size of 5 × 5 nm2 were separated by 1–2 nm wide clean Cu surface. Oxygen molecules are selectively dissociated on the clean Cu area, where the nitrogen-adsorbed patches inhomogeneously induce the compressive surface stress. The oxygen adsorbates are located at the fourfold hollow sites of the clean Cu surface, and migrate only on the clean surface without changing the nitrogen-adsorbed patches. Both the dissociation probability of oxygen molecule and the diffusion barrier of the oxygen adsorbates are small on the highly compressed area. When the local density of oxygen adsorbates exceeds 1/3 of the Cu atom density at (0 0 1) surface, the surface becomes disordered.