STM Movie of Cu(I) Halide Formation

After saturation of a chemisorbed layer of Br atoms, continued Br₂ exposure leads to the formation of CuBr.  This movie shows a 79 x 79 nm area of a Cu surface vicinal to (100) during reaction with Br₂ to form CuBr.  When the movie starts considerable reaction has already taken place.  There are several things to look for during the movie.  First, the reaction consumes Cu atoms from the steps causing the steps to recede.  This does not happen uniformly at the steps but rather the reaction is faster in some locations than others, in places this results in channels etched into the terraces.  The Cu halide formed by reaction nucleates clusters at locations other than where the reaction took place;  diffusion of some of the small halide nuclei can be seen in the movie.  At the top of the images, halide clusters can be seen along the step.  Notice that these clusters do not block the reaction.  Each frame of the movie was recorded in 7 sec.