Published online by Cambridge University Press: 15 February 2011
We have elucidated the atomic structure of the γ-phase, which appears at 1ML coverage of Al on the Si (111) surface, using scanning tunneling Microscopy (STM). The structure is based on the 9×9 dimer-adatom-stacking fault (DAS) structure. Al atoms replace Si atoms in the second layer of the DAS Model. As a result, excess silicon atoms are produced during the formation of the γ-phase and migrate on the surface to form Monatomic-height islands. The area ratio of the upper and lower terraces is in good agreement with the proposed formation Mechanism.