Adsorbate-mediated step transformations and terrace rearrangement of Si(100)-(2x1)

Scanning tunneling microscopy and density-functional theory have been combined to demonstrate structural transformations of steps of Si(100)-(2x1) induced by nondangling bond-terminated Cl adsorbates. We identify a stable, bridge-bonded step adsorption site and show that supersaturation facilitates the population of those sites, leading to rebonded atom etching, step retreat, and extensive terrace rearrangement from the diffusion of resultant atomic vacancy lines across the supersaturated surface. Similarities to H-Si(100) are briefly discussed.