Observation of local electronic structures of adatom vacancies in Si(111)-(7x7) surface in real space

The evolution of the local electronic structure of the Si(111)-(7x7) surface containing adatom vacancies is resolved by energy-dependent scanning tunneling microscopy. The dI/dV images show clear and rich features that are bias dependent and can be sorted into several patterns. The probed dI/dV patterns reflect the different hybridized electronic features arising from the adatom vacancies. A typical electronic state associated with the single adatom vacancy in the surface is experimentally found to be at about 0.55 eV below the Fermi energy level, which is essentially attributed to the two upward backbone atoms around the adatom vacancy. We also find that adatom vacancies can induce the images of some rest atoms to be invisible in the dI/dV maps.