Gallium-induced perturbations of the Ge(111)-c(2×8) reconstruction

With the scanning tunneling microscope we investigated defects produced by small amounts of Ga on Ge(111)-c(2×8). The studied surfaces were prepared either using Ga-doped crystals (concentration up to 1×${10}^{19}$ ${\mathrm{cm}}^{\mathrm{-}3}$) or depositing Ga (up to 0.05 monolayer) from an effusion cell. Each surface area was studied in the constant-current mode for two different bias values (dual-polarity imaging), thus providing electronic and structural information for each defect. Ga atoms were found to substitute for rest atoms preserving the c(2×8) reconstruction. Defects in which adatoms occupy ${\mathit{H}}_3$ sites as well as those which break the c(2×8) long-range order are discussed.