Ca-induced structural transformation of the single-domain Si(001) surface: CaF2/Si(001)-4° off

By scanning tunneling microscopy and synchrotron photoemission spectroscopy, it has been found that through CaF2 exposure to the single-domain Si(001)-4° off surface held at 750 °C, Si dimers on Si(001) terraces are replaced preferentially by dissociated Ca atoms while F atoms are desorbed. The resulting 2 × 3 reconstruction saturates the (001) terraces at a coverage between 0.1 and 0.3 monolayers. Additional CaF2 exposure triggers a structural transformation to a stable hill-and-valley structure composed of wider (001)-2 × 3 terraces and compensating facets comprised of (11 17) and (11 13) units, both with a 6 × 1 surface reconstruction. This study demonstrates that the periodic width of the single domain Si(001) surface can be modulated through adsorbing Ca atoms while maintaining one-dimensional symmetry along the DB steps and the semiconducting nature of the surface.