Br₂ Etching of Cu(100)

When Cu(100) is exposed to bromine, a c(2x2) layer of adsorbed Br atoms rapidly forms. In the c(2x2) layer, every other four-fold hollow adsorption site on the surface is filled. Continued exposure to Br₂ results in the slow formation of CuBr. Copper atoms for CuBr formation are preferentially withdrawn from steps on the surface. This image shows that the removal of Cu atoms from the step is not isotropic, rather some sections of the steps are more reactive than others resulting in the peninsula shown above. The image shows the c(2x2) structure of the adsorbed Br atoms and a peninsula that is one Cu atom higher than the rest of the surface. The CuBr formed by reaction aggregates into clusters that are observed on other areas of the surface. This image was recorded at room temperature, at temperatures above ~450 K, the CuBr formed by reaction sublimes, thus removing Cu and etching the surface.