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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.

We pursue dynamic charge and occupancy modulation of silicon dangling bond sites on H-Si(100)-2 × 1 with a biased scanning tunneling microscope tip and demonstrate that the reactivity and mechanism of product formation of cyclobutylmethylketone (CBMK) on the surface at the active sites may be thus spatially regulated. Reactivity is observed to be dependent on the polarity between tip and surface while the area over which reactivity modulation is established scales according to the dopant concentration in the sample. We account for these observations with examination of the competition kinetics applicable to the CBMK/H-Si reaction and determine how said kinetics are affected by the charge state of DB sites associated with reaction initiation and propagation. Our experiments demonstrate a new paradigm in lithographic control of a self-assembly process on H-Si and reveal a variant to the well-known radical mediated chain reaction chemistry applicable to the H-Si surface where self-assembly is initiated with dative bond formation between the molecule and a DB site. [ABSTRACT FROM AUTHOR]