Two reaction channels directly observed for atomic hydrogen on the Si(111)-7×7 surface

Using scanning tunneling microscopy and spectroscopy, we have investigated the reaction of atomic hydrogen with the Si(111)-7×{}7 reconstructed surface. A simple picture evolves in which the reaction proceeds concurrently along two channels: a direct binding of the hydrogen atoms to the existing dangling bonds of the surface, and a slower removal of the uppermost Si layer and binding of the hydrogen atoms to the created dangling bonds of the next layer.