Stabilizing influence of double bonds on the Si(111)-(3 x 1) and Ge(111)-(3 x 1) surface reconstructions: new experimental evidence

We have obtained new real-space images of the filled dangling-bond states o f the alkali-metal-induced (3 x 1) reconstruction of the Si(111) surface as sociated with recently proposed Si=Si double-bond surface structures. Our n ew experimental evidence reveals significant subtle differences between thi s local bonding on Na/Si(111)-(3 x 1) and Na/Ge(111)-(3 x 1) which argues a strong case for the proposed 'honeycomb chain-channel model' but with a re laxation of a strict double-bond requirement, particularly on the germanium surface. (C) 2000 Elsevier Science B.V. All rights reserved.