The Ge(111)-c(2 x 8) and related surfaces were examined in detail using scanning tunnelling microscopy. A comparison of tunnelling images, in both the filled and empty states, for the Ge(111) surface and similar images for the Si(111)-(5 x 5), -(7 x 7) and -(9 x 9) surfaces revealed the structures to be inconsistent with previous models. A comparison with filled- or empty-state images for the laser-stabilized Si(111) surface showed that both this surface and Ge(111)-c(2 x 8) were most consistent with a simple model of alternating rows of 2 x 2 and c(4 x 2) adatoms on T4 sites on a 1 x 1 substrate. No evidence was found, in the tunnelling images of Ge(111)-c(2 x 8), to support the existence of a sub-surface stacking fault. Electronic and geometrical sources for the contrast in the tunnelling images were considered and it was concluded that the electronic structure formed the basis for the images of adatom-reconstructed semiconductor surfaces. Dimer–Adatom–Stacking-Fault (DAS) and Non-DAS (111) Semiconductor Surfaces - a Comparison of Ge(111)-c(2 x 8) to Si(111)-(2 x 2), -(5 x 5), -(7 x 7), and -(9 x 9) with Scanning Tunneling Microscopy. R.S.Becker, B.S.Swartzentruber, J.S.Vickers, T.Klitsner: Physical Review B, 1989, 39, 1633-47