Step structure and surface morphology of hydrogen-terminated silicon: (0 0 1) to (1 1 4)

We have determined the equilibrium step structures and surface morphology for the whole range of monohydride-terminated (0 0 1)-terrace-plus-step silicon surfaces using scanning tunneling microscopy. The transformation in the equilibrium Si surface morphology caused by H-termination can be categorized into three different regimes delineated by the types of steps present on the clean surfaces. On nominal Si(0 0 1), the single-layer height B-type steps (SB) are mostly non-rebonded and rougher after H passivation. On surfaces dominated by double-layer height B-type steps (DB), such as Si(1 1 11), the non-rebonded DB and SB steps show a lower formation energy. Measurements on post-annealed surfaces indicate that the DB step formation energies strongly depend on H chemical potential. Smoother morphologies are observed following H-termination of surfaces oriented approximately between (1 1 7) and (1 1 4). This effect is quite apparent on Si(1 1 5), where the monohydride surface exhibits large (1 1 5)-(2 × 2) domains, a structure not observed on the clean surface. All of these structural modifications result directly from a change in the relative energies of the possible single- and double-layer step configurations.