Tunnel coupled dangling bond structures on hydrogen terminated silicon surfaces

We study both experimentally and theoretically the electronic behavior of dangling bonds (DBs) at a hydrogen terminated Si(100)-2×1 surface. Dangling bonds behave as quantum dots and, depending on their separation, can be tunnel coupled with each other or completely isolated. On n-type highly doped silicon, the latter have a net charge of -1e, while coupled DBs exhibit altered but predictable filling behavior derived from an interplay between interdot tunneling and Coulomb repulsion. We found good correlation between many scanning tunneling micrographs of dangling bond structures and our theoretical results of a corresponding extended Hubbard model. We also demonstrated chemical methods to prevent tunnel coupling and isolate charge on a single dangling bond.